The authors would like to thank Prof. Sze-Bi Hsu and Ms. Zhenzhen for useful discussions and help in the theoretical analysis and numerical simulation. Y. T. Y. would like to acknowledge funding support from the Ministry of Science and Technology under grant numbers MOST 103-2220-E-007-026 and MOST 104-2220-E-007-011, and from the National Tsing Hua University under grant numbers 103N2042E1, 104N2042E1, and 105N518CE1.

1. Montaggio e Pretesting del dispositivo Morbidostat <ol><li> Assemblea della Morbidostat <ol><li> Punzone 3 fori sul tappo del flacone di coltura con una siringa 18 G. Tagliare tre pezzi di tubo di polietilene ~ 7 cm di lunghezza. Inserire questi tre pezzi di tubo di polietilene sul tappo. </li><li> Utilizzare nastro per avvolgere il bordo della calotta per servire come il cast per la miscela polidimetilsilossano (PDMS). Miscelare 5 g di un componente e 0,5 g di componente B dei PDMS in un contenitore di plastica 150 ml agitando manualmente con uno stuzzicadenti. Caricare il composto in una siringa da 10 ml. <ol><li> Versare il composto PDMS sul tappo con la siringa. Cuocere tutto il tappo per curare il PDMS per 8 ore in forno a 70 ° C. </li></ol></li><li> Saldare l&#39;anodo LED con il filo calibro 24 e catodo LED con il resistore carbonio con un saldatore. Saldare una resistenza di 680 Ω carbonio con un filo di 24 g. Isolare il collegamento del filo con nastro isolante. </li><li> Cosìlder collettore del fotorivelatore con il filo 24 G e l&#39;emettitore del fotorivelatore con una resistenza di carbonio 100 k. Isolare il collegamento del filo con nastro isolante. </li><li> Posizionare il diodo emettitore di luce nel supporto coltura flacone. Seguendo lo schema del circuito di Figura integrativa 2, collegare il diodo emettitore di luce e potenza con una alimentazione di 5 V. Assicurarsi che il LED funziona utilizzando una fotocamera digitale in grado di rilevare IR (ad esempio, una fotocamera del cellulare). </li><li> Posizionare il fotorivelatore nel supporto coltura flacone. Seguendo lo schema circuitale di figura integrativa 2, collegare il fotorivelatore e potenza con una alimentazione di 5 V. Collegare il filo su entrambi i lati dei resistori fotorivelatori per misurare la tensione attraverso la scheda elettronica di controllo. </li><li> Colla un magnete sull&#39;albero della ventola di raffreddamento, che serve come unità di agitatore magnetico. Si noti che il alignment dell&#39;albero del ventilatore alla fiala coltura, e la distanza tra il flaconcino coltura e il magnete è molto critico per il corretto funzionamento dell&#39;unità agitazione magnetica. </li><li> Collegare ogni pezzo di tubo in polietilene del flaconcino cultura nel corrispondente pezzo di tubo in silicone per le micro-pompe, bottiglie medie, e di scarto. Accendere la pompa per 1 ora e misurare il volume totale pompato dalla bottiglia mezzo al flaconcino coltura per determinare la velocità della pompa. Notare che la velocità di pompaggio tipica dovrebbe essere ~ 4 ml / hr, che corrisponde al grado di diluizione D = 0.33 h -1 per 12 ml di volume del flacone coltura lavorativi. </li><li> Mettere il tutto in una di medie dimensioni (34 cm x 34 cm x 43,5 centimetri) agitatore incubatore. </li></ol></li><li> Pretesting il Morbidostat <ol><li> Imposta la tensione di alimentazione del ventilatore freddo a 5 V per iniziare il suo motore di testare la barra di agitazione magnetica. Si noti che l&#39;azione di agitazione può essere ispezionato visivamente. La tensione che guidanos il motore della ventola di raffreddamento è controllato con precisione da modulazione di larghezza di impulso (PWM). </li><li> Preparare una serie di wild type E. campioni coli con densità ottica a 600 nm in genere vanno 0,07-0,3 per la calibrazione. Posizionare un test E. campione coli nella fiala cultura e registrare la tensione cellula fotoelettrica. <ol><li> Inserire ~ 100 microlitri dello stesso campione nel lettore di piastre e registrare la densità ottica. Utilizzare la tensione fotorilevatore contro i dati della densità ottica per tracciare la curva di calibrazione. Si noti che in genere, una variazione unitaria di densità ottica corrisponde a ~ 7,6 V cambiamento nella cellula fotoelettrica con lo schema di polarizzazione usato qui. </li></ol></li></ol></li></ol> 2. L&#39;esecuzione del Morbidostat <ol><li> Preparazione Prima di iniziare l&#39;esperimento giornaliera <ol><li> Preparare la fiala cultura con tre resistenti tubi ultra-chimici TYGON con diametro interno 1/32 pollici e diametro esterno 3/32 di pollice per ingressi per formare il dispositivo come nella sezione1.1 e nella Figura 1 supplementare. </li><li> Preparare il supporto M9 minima (0,2% di glucosio) e trimetoprim (TMP) farmaco contenente mezzo. Sterilizzare il mezzo, la bottiglia mezzo, la bottiglia mezzo droga, la bottiglia degli scarti e la fiala coltura in autoclave a 121 ° C. NOTA: Il TMP è una soluzione madre che viene utilizzato per realizzare successivamente le concentrazioni in tabella 1 e il farmaco contenente TMP mezzo non è autoclave. </li></ol></li><li> Esecuzione del Morbidostat <ol><li> Il primo giorno dell&#39;esperimento, scongelare 1 ml di tipo selvaggio congelato E. cellule coli MG1655 per 5 min a temperatura ambiente e trasferimento 120 ml di cellule al flacone di coltura contenente ~ 12 ml di mezzo di crescita M9. Dopo il primo giorno, scongelare 1 ml di E. congelati coli cellule dal giorno precedente per 5 minuti e il trasferimento 120 ml di cellule ad una nuova fiala di coltura contenente ~ 12 ml di mezzo di crescita M9. </li><li> Accendere l&#39;incubatore shaker e impostare la tempe<html> ratura di 30 ° C senza agitazione. </li><li> Avviare l&#39;operazione morbidostat accendendo la micro-pompa, l&#39;unità di agitazione magnetica, e la misurazione della densità ottica. NOTA: Durante il funzionamento, un algoritmo di soglia di feedback è utilizzato per controllare l&#39;iniezione di droga. Quando la densità ottica misurata supera una soglia prefissata, la pompa di iniezione farmaco potrebbe essere attivata e la pompa mezzo verrebbe disattivata. Altrimenti, la pompa di iniezione di droga rimane spento e la pompa del mezzo è acceso. </li><li> Monitorare la tensione di volta in volta a garantire il crescita microbica. Nota: A causa del gelo e disgelo, E. coli cellule mostrano un ritardo di ~ 4 ore durante la crescita di ogni giorno. </li><li> Dopo ~ 23 ore, fermare la micro-pompa disattivando la sua tensione di alimentazione ed estrarre la fiala cultura. Aggiungere 15% glicerolo nel flaconcino coltura e congelare il campione a -80 ° C per la conservazione. </li><li> Ripetere i passaggi da 2.2.1 a 2.2.5. </li></ol></li></ol>Le &quot;&gt; 3. antibiotico suscettibilità Misura in 96 Well Format NOTA: Eseguire la misurazione tasso di crescita in un lettore di piastre con un formato ben 96 per determinare il livello di resistenza agli antibiotici. <ol><li> Scongelare il campione congelato giornaliera a temperatura ambiente per 5 minuti e trasferire 15 microlitri della cella alla fiala di coltura contenente ~ 15 ml M9 medie. Consentire loro di crescere fino a quando la densità ottica a 600 nm raggiunge ~ 0.1. Dividere i 15 ml in 1 ml flaconi e aggiungere il farmaco TMP in questa fase per ottenere le concentrazioni di farmaco desiderati come mostrato nella Tabella 1. </li><li> Prendete 200 ml di campione dal punto 3.1 e il luogo in ciascun bene nel lettore di piastre e permettere loro di crescere per 12 ore 5. La densità ottica alla lunghezza d&#39;onda di 600 nm viene registrato automaticamente durante la misurazione. NOTA: Per ogni punto di dati, le misurazioni triplice copia sono registrati e una media per garantire la coerenza dei dati. I dati sulla densità ottica in funzione del tempo può be utilizzato per ottenere il tasso di crescita. </li><li> Tracciare i dati tasso di crescita rispetto al concentrazione di farmaco per ottenere IC50. Notare che IC 50 è definita come la concentrazione di farmaco in cui la velocità di crescita è il cinquanta per cento del tasso di crescita massimo 5. </li></ol> 4. Single Cell Morfologia ed un antibiotico suscettibilità di misura in dispositivi microfluidici <ol><li> Eseguire la fabbricazione dei dispositivi microfluidici tramite litografia soft multistrato da PDMS come descritto altrove 15. <ol><li> Utilizzare fotolitografia per fare lo stampo photoresist per gli strati di controllo e di flusso. Si noti che per il livello di controllo, utilizzare fotoresist negativo (~ 15 micron altezza) e photoresist positivo (~ 8 micron altezza) per produrre uno stampo su un wafer di silicio nudo. </li><li> Preparare miscele PDMS con rapporti reticolazione 5: 1 e 20: 1 per il livello di controllo e lo strato flusso rispettivamente. Mettere le miscele in un essiccatore sotto vuoto per eliminare eventuali bolle, Per 1 ora. </li><li> Esporre i controllo stampi strato di resina fotosensibile su wafer di silicio per trimetilclorosilano (TMCS) vapore. Rendere il livello di controllo dello spessore ~ ​​6 mm con colata la miscela PDMS (con rapporto di reticolazione 5: 1) sul wafer di silicio sullo stampo di controllo strato di resina fotosensibile. Cuocere il livello di controllo per 40 min a 80 ° C per 1 ora in forno. </li><li> Rendere lo strato flusso mediante centrifuga rivestendo una miscela PDMS (con rapporto di reticolazione 20: 1, velocità di centrifuga 3000 rpm per 60 sec) su uno stampo photoresist strato di flusso. Cuocere il livello di flusso per 30 min a 80 ° C per 1 ora in forno. </li><li> Utilizzare una lama di rasoio per tagliare il livello di controllo nella dimensione del chip desiderato (in genere tre centimetri x 2 cm) e staccare manualmente il livello di controllo. Posizionare il livello di controllo sulla parte superiore dello strato flusso e allinearli allo stereomicroscopio. Curare il gruppo allineato a 80 ° C nella notte forno. Successivamente, immergere l&#39;assemblaggio in 250 ml di acqua deionizzata in un contenitore di plastica per 5 ore per sciogliere il residuo TMCS. </li><li> Successivamente, perforare i fori di ingresso con 20 aghi G e legare l&#39;intera elastomero su un vetrino rivestito con uno strato PDMS vuoto (PDMS reticolazione rapporto 5: 1, velocità di centrifuga di 2000 rpm per 30 sec) mediante trattamento plasma ad aria per 40 sec a 1.2 pressione dell&#39;aria Torr. </li><li> Effettuare vasta cottura per 36 ore a 80 ° C per ridurre gli effetti citotossici di PDMS. Si noti che questa fase di cottura è fondamentale per minimizzare la tossicità per le cellule batteriche. </li></ol></li><li> On Chip crescita Experiment <ol><li> Prima di caricare nel dispositivo microfluidica, lavare con acqua deionizzata per 1 ora e mezzo di M9 per 1 ora. </li><li> Scongelare il campione congelato giornaliera a temperatura ambiente per 5 minuti e inoculare una nuova provetta con terreno M9 fresco. Trasferire il campione in un incubatore shaker a 37 ° C durante la notte. </li><li> Diluire il microbica campione di 10 volte con media M9 e caricarlo nel dispositivo microfluidica facendo pressioni il contenitore del campione microbica a 5 psi. Quindi caricare il farmaco TMPmedio nel chip facendo pressioni contenitore mezzo farmaco a 5 psi. Eseguire la miscelazione tra microbi e droga azionando la valvola micromeccanico tra le due camere sul chip microfluidico per 15 min. </li><li> Posizionare il chip microfluidico nell&#39;incubatore microscopio montato sul microscopio invertito. Acquisire l&#39;immagine cellule nella camera di crescita ogni ora per 8 ore con la camera CCD montata sul microscopio invertito. </li><li> Utilizzare lo script programma personalizzato per calcolare i numeri di cellulare attraverso un algoritmo di soglia sui dati di immagine cellule 18. Si noti che i dati numerici delle cellule sono in media in genere oltre tre camere microfluidica. </li></ol></li></ol>

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The authors have nothing to disclose.

Un dispositivo morbidostat a basso impatto da componenti a basso costo è dimostrata. Gli aumenti di livello resistenza ai farmaci registrati dal dispositivo sono coerenti con quelli di precedenti rapporti di 5. Progettato per gli studi evolutivi di resistenza ai farmaci, il dispositivo è potenzialmente applicabile a molti altri esperimenti. In primo luogo, un database completo di mutazioni indotte da farmaci può essere stabilita per un ampio insieme di antibiotici clinicamente rilevanti. Ad esempio, il per...

Dal momento che l&#39;introduzione del primo penicillina antibiotico, microbica resistenza agli antibiotici è trasformata in un problema di salute globale 1. Sebbene l&#39;acquisizione di resistenza agli antibiotici può essere studiato retrospettivamente in vivo, le condizioni di questi esperimenti sono spesso non controllati durante l&#39;intera evoluzione 2. In alternativa, adaptive evoluzione di laboratorio può rivelare l&#39;evoluzione molecolare di una specie microbiche sotto stress ambientali o pressione selettiva da un farmaco antibiotico 3. Recentemente, molti esperimenti evolutivi ben controllati di resistenza ai farmaci antibiotici hanno chiarito la comparsa di resistenza ai farmaci antibiotici. Ad esempio, il gruppo di Austin ha dimostrato rapido emergere in un microfluidica correttamente progettato ambiente compartimenti 4. Il morbidostat recentemente sviluppato induce mutazioni sistematiche sotto farmaco pressione selettiva 5,6. Il morbidostat, un Selec microbicaDispositivo zione che regola continuamente la concentrazione di antibiotico per mantenere una popolazione quasi costante, è un importante progresso dal test di fluttuazione utilizzato in microbiologia 7,8. Nel test di fluttuazione, un antibiotico viene iniettato ad alta concentrazione, ei mutanti sopravvissuti sono schermate e contati. Invece, i microbi in un morbidostat sono costantemente in discussione e acquisiscono mutazioni multiple. Il morbidostat funziona in modo simile al chemostat, un dispositivo di cultura inventato da Novick e Szliard nel 1950 che mantiene una popolazione costante fornendo continuamente nutrienti mentre diluendo la popolazione microbica 9. Fin dalla sua introduzione, il chemostat è stata avanzata e migliorata. Attuali chemostati microfluidica hanno raggiunto capacità nanolitri e unicellulari. Tuttavia, questi dispositivi non sono adatti per esperimenti evoluzione adattativa, che richiedono una grande popolazione di cellule con molti eventi mutazione 10,11. Recentemente, mini-chemostati con volumi di lavoro del ~ 10 ml sono stati sviluppati per colmare il divario tra bioreattori scala litri e la microfluidica chemostat 12,13. Qui vi presentiamo la progettazione e l&#39;utilizzo di un basso costo, morbidostat automatizzato per uno studio della resistenza ai farmaci antibiotici. Il modulo proposto può essere impiegato in un incubatore shaker in un laboratorio di microbiologia con requisiti hardware minimi. Il firmware open-source è anche facilmente su misura per applicazioni specifiche di evoluzione adattativa, come l&#39;ingegneria metabolica 3. Infine, il morbidostat è integrato in una piattaforma microfluidica multiplato per i test di suscettibilità antibiotica 14.

<table border="0" cellpadding="0" cellspacing="0" width="797">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Environmental Shaker Incubator</td>
			<td style="width:135px;">BioSan</td>
			<td style="width:163px;">ES-20</td>
			<td style="width:227px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Arduino Leonardo board</td>
			<td style="width:135px;">Arduino</td>
			<td style="width:163px;">Leonardo</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">680 Ohm Carbon Resistor</td>
			<td style="width:135px;">Digikey</td>
			<td style="width:163px;"></td>
			<td>Bias resistor for LED</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">100k Ohm Carbon resistor</td>
			<td style="width:135px;">Digikey</td>
			<td style="width:163px;"></td>
			<td>Bias resistor for phototransistor</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:275px;">940 nm light emitting diode</td>
			<td style="width:135px;">Bright LED Electronic</td>
			<td style="width:163px;">BIR-BM13E4G-2</td>
			<td>Optical density measurement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">940 nm phototransistor</td>
			<td style="width:135px;">Kodenshi&#160;</td>
			<td style="width:163px;">ST-2L2B</td>
			<td>Optical density measurement</td>
		</tr>
		<tr height="57">
			<td height="57" style="height:57px;">Darlington pair IC Toshiba</td>
			<td style="width:135px;">Mouser</td>
			<td style="width:163px;">ULN2803APG</td>
			<td style="width:227px;">&#160;this IC drives micropumps and magnetic stirring unit</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:275px;">5V DC brushless fan&#160;</td>
			<td style="width:135px;">ADDA</td>
			<td style="width:163px;">AD0405LX-G70</td>
			<td style="width:227px;">spec: 5V supply voltage and 80mA available www.jameco.com</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Piezoelectric micropump</td>
			<td style="width:135px;">CurieJet</td>
			<td style="width:163px;">PS15I-FT-5L</td>
			<td>Pressure &#62;3kPa&#160; Flow rate &#62;5 ml/min</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Tygon 3350 Tuning</td>
			<td style="width:135px;">Saint Gobain</td>
			<td style="width:163px;">ABW00001</td>
			<td>ID: 1/32&#34; OD: 3/32&#34; L:50&#39;&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Magnetic Stir bar</td>
			<td style="width:135px;">COWIE</td>
			<td style="width:163px;"></td>
			<td>tapered shape dim: 10 mm x 4mm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:275px;">Glass scintillation 20ml vial</td>
			<td style="width:135px;">DGS</td>
			<td style="width:163px;"></td>
			<td>Pyrex glass 28mm(dia.)x 61 mm(h)</td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:275px;">Culture vial holder</td>
			<td style="width:135px;"></td>
			<td style="width:163px;"></td>
			<td>Custom made from Polyformaldehyde&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Silicone&#160;</td>
			<td style="width:135px;">Dow Corning</td>
			<td style="width:163px;">Sylgald 184</td>
			<td>used to seal the glass vial</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Medium bottle</td>
			<td style="width:135px;">VWR</td>
			<td style="width:163px;">66022-065</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Difco M9 minimal salt 5x</td>
			<td style="width:135px;">BD</td>
			<td style="width:163px;"></td>
			<td>Medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Cadamino Acid</td>
			<td style="width:135px;">BD</td>
			<td style="width:163px;"></td>
			<td>Medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">glucose</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:163px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Agar Bateriological</td>
			<td style="width:135px;">Oxoid</td>
			<td style="width:163px;"></td>
			<td>for agar plate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Luria Bertani medium</td>
			<td style="width:135px;"></td>
			<td style="width:163px;"></td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:275px;">Inverted microscope</td>
			<td style="width:135px;">Leica Microsystems</td>
			<td style="width:163px;">Leica DMI-LED</td>
			<td style="width:227px;">used for microfluidic measurement Use X40 objective NA=0.55</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:275px;">Microscope Incubator</td>
			<td style="width:135px;">Live Cell Instrument</td>
			<td style="width:163px;">CU-109</td>
			<td>used for microfluidic measurement</td>
		</tr>
		<tr height="49">
			<td height="49" style="height:49px;width:275px;">Solenoidal valves</td>
			<td style="width:135px;">Pneumadyne</td>
			<td style="width:163px;">S10MM-31-12-3</td>
			<td>Normally open 1.3 Watt 12 Vdc</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">USB interface card</td>
			<td style="width:135px;">Hobby Engineering</td>
			<td>USBIO24-R Digital I/O Module&#160;</td>
			<td>for microfluidics measurement</td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:275px;">Air compressor</td>
			<td style="width:135px;">Rocker Scientific</td>
			<td style="width:163px;">ROCKER 440</td>
			<td style="width:227px;">Pressure source for microfluidcs Max. Pressure 80 Psi</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Male luer-lock fittings to 1/8&#34; barb</td>
			<td>ValuePlastics.com</td>
			<td style="width:163px;">MTLL230-1</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1/8&#34; barb to 10-32 threaded port</td>
			<td>ValuePlastics.com</td>
			<td style="width:163px;">B-1</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Female luer-lock fittings to 10-32 threaded port</td>
			<td>ValuePlastics.com</td>
			<td style="width:163px;">KFTL-1</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NPN darlington transistor 500mA, 40V (2N6427)</td>
			<td>DigiKey.com</td>
			<td>2N6427GOS-ND</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">10kOhm, carbon film resistor, 0.25W</td>
			<td>DigiKey.com</td>
			<td>P10KBACT-ND</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tantalum capacitor, 10uF, 25V, 10%</td>
			<td>DigiKey.com</td>
			<td>478-1841-ND</td>
			<td>used for microfluidic control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Andor CCD camera</td>
			<td style="width:135px;">Andor</td>
			<td style="width:163px;">Zyla 4.2 Plus SCMOS</td>
			<td>used for microfluidic on chip imaging</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">ELISA plate reader</td>
			<td style="width:135px;"></td>
			<td style="width:163px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">two component Silicone&#160;</td>
			<td style="width:135px;">Momentive</td>
			<td style="width:163px;">RTV 615</td>
			<td>used for microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">SU-8 photoresist</td>
			<td style="width:135px;">Micrchem</td>
			<td style="width:163px;">SU8 2015</td>
			<td>used for microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">AZ4620 photoresist</td>
			<td style="width:135px;">Clariant</td>
			<td style="width:163px;">AZ 4620</td>
			<td>used for microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Plasma cleaner</td>
			<td style="width:135px;">Harrick Plasma</td>
			<td style="width:163px;">PDC 32G</td>
			<td>used for microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">20 Gauge Syringe Needle</td>
			<td style="width:135px;">BD</td>
			<td style="width:163px;"></td>
			<td>used for microfluidic chip fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Labcycler</td>
			<td style="width:135px;">Sensoquest</td>
			<td style="width:163px;">Labcycler</td>
			<td>PCR&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">DNA polymerase</td>
			<td style="width:135px;">Toyobo</td>
			<td style="width:163px;">KDO Plus</td>
			<td>PCR amplification</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Trimethoprim</td>
			<td style="width:135px;">Sigma</td>
			<td style="width:163px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:275px;">Plate reader</td>
			<td style="width:135px;">Biotek</td>
			<td style="width:163px;">Synergy H1 hybrid&#160;</td>
			<td>antibiotic resistane measurement</td>
		</tr>
	</tbody>
</table>

design and use of a low cost, automated morbidostat for adaptive evolution of bacteria under antibiotic drug selection

Descriviamo un basso costo, morbidostat configurabile per caratterizzare il percorso evolutivo della resistenza agli antibiotici. Il morbidostat è un dispositivo di coltura batterica che controlla continuamente la crescita batterica e regola dinamicamente la concentrazione di farmaco di sfidare costantemente i batteri si evolvono per acquisire resistenza ai farmaci. Il dispositivo è dotato di un volume di lavoro di ~ 10 ml ed è completamente automatizzato e dotato di misura della densità ottica e micro-pompe per medio e la somministrazione di farmaci. Per convalidare la piattaforma, abbiamo misurato l&#39;acquisizione graduale della resistenza trimetoprim in Escherichia coli MG 1655, e integrato il dispositivo con una piattaforma microfluidica multiplex per indagare la morfologia cellulare e sensibilità agli antibiotici. L&#39;approccio può essere up-scalata a studi di laboratorio di resistenza ai farmaci antibiotici, ed è estendibile a adattivo evoluzione per i miglioramenti di deformazione in ingegneria metabolica e altri esperimenti di coltura batterica.

Il morbidostat sopra descritto è schematizzato in Figura 1. Le operazioni morbidostat comuni, tra evoluzione sperimentale, test di sensibilità agli antibiotici e controllo della morfologia cellulare, sono stati convalidati in E. cultura coli MG1655 esposti a trimetoprim (TMP), un antibiotico comunemente usato 5,6. TMP induce molto particolari graduali aumenti di resistenza ai farmaci, e le mutazioni sono raggruppati intorno al gene diidrofo...

Watch this Scientific Journal Video about Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection at JoVE.com

Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection

We describe a low cost, configurable morbidostat that enables the characterization of antibiotic drug resistance by dynamically adjusting the drug concentration. The device can be integrated with a multiplexed microfluidic platform. The approach can be scaled up for laboratory antibiotic drug resistance studies.

Progettazione e l&#39;uso di un basso costo, Automated Morbidostat per Adaptive Evolution di batteri sotto antibiotici selezione dei farmaci

We describe a low cost, configurable morbidostat for characterizing the evolutionary pathway of antibiotic resistance. The morbidostat is a bacterial ...

design-use-low-cost-automated-morbidostat-for-adaptive-evolution

Research

JoVE Journal

Genetics

9.6K Views.  National Tsing Hua University. We describe a low cost, configurable morbidostat that enables the characterization of antibiotic drug resistance by dynamically adjusting the drug concentration. The device can be integrated with a multiplexed microfluidic platform. The approach can be scaled up for laboratory antibiotic drug resistance studies.

Video: Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection

Procedure for Adaptive Laboratory Evolution of Microorganisms Using a Chemostat

Natural evolution involves genetic diversity such as environmental change and a selection between small populations. Adaptive laboratory evolution (ALE) refers to the experimental situation in which evolution is observed using living organisms under controlled conditions and stressors; organisms are thereby artificially forced to make evolutionary changes. Microorganisms are subject to a variety of stressors in the environment and are capable of regulating certain stress-inducible proteins to increase their chances of survival. Naturally occurring spontaneous mutations bring about changes in a microorganism's genome that affect its chances of survival. Long-term exposure to chemostat culture provokes an accumulation of spontaneous mutations and renders the most adaptable strain dominant. Compared to the colony transfer and serial transfer methods, chemostat culture entails the highest number of cell divisions and, therefore, the highest number of diverse populations. Although chemostat culture for ALE requires more complicated culture devices, it is less labor intensive once the operation begins. Comparative genomic and transcriptome analyses of the adapted strain provide evolutionary clues as to how the stressors contribute to mutations that overcome the stress. The goal of the current paper is to bring about accelerated evolution of microorganisms under controlled laboratory conditions.

Here, we present a protocol to obtain adaptive laboratory evolution of microorganisms under conditions using chemostat culture. Also, genomic analysis of the evolved strain is discussed.

Procedura per l&#39;Adaptive Laboratorio evoluzione dei microrganismi Utilizzando un chemostat

Natural evolution involves genetic diversity such as environmental change and a selection between small populations. Adaptive laboratory evolution (ALE) ...

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Genetica

Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

Multicopy plasmids are extremely abundant in prokaryotes but their role in bacterial evolution remains poorly understood. We recently showed that the increase in gene copy number per cell provided by multicopy plasmids could accelerate the evolution of plasmid-encoded genes. In this work, we present an experimental system to test the ability of multicopy plasmids to promote gene evolution. Using simple molecular biology methods, we constructed a model system where an antibiotic resistance gene can be inserted into Escherichia coli MG1655, either in the chromosome or on a multicopy plasmid. We use an experimental evolution approach to propagate the different strains under increasing concentrations of antibiotics and we measure survival of bacterial populations over time. The choice of the antibiotic molecule and the resistance gene is so that the gene can only confer resistance through the acquisition of mutations. This &#34;evolutionary rescue&#34; approach provides a simple method to test the potential of multicopy plasmids to promote the acquisition of antibiotic resistance. In the next step of the experimental system, the molecular bases of antibiotic resistance are characterized. To identify mutations responsible for the acquisition of antibiotic resistance we use deep DNA sequencing of samples obtained from whole populations and clones. Finally, to confirm the role of the mutations in the gene under study, we reconstruct them in the parental background and test the resistance phenotype of the resulting strains.

Here we present an experimental method to test the role of multicopy plasmids in the evolution of antibiotic resistance.

Prova il ruolo dei plasmidi multicopia nell'evoluzione della resistenza agli Antibiotico

Multicopy plasmids are extremely abundant in prokaryotes but their role in bacterial evolution remains poorly understood. We recently showed that the ...

Genome-wide Surveillance of Transcription Errors in Eukaryotic Organisms

Accurate transcription is required for the faithful expression of genetic information. Surprisingly though, little is known about the mechanisms that control the fidelity of transcription. To fill this gap in scientific knowledge, we recently optimized the circle-sequencing assay to detect transcription errors throughout the transcriptome of Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans. This protocol will provide researchers with a powerful new tool to map the landscape of transcription errors in eukaryotic cells so that the mechanisms that control the fidelity of transcription can be elucidated in unprecedented detail.

This protocol provides researchers with a new tool to monitor the fidelity of transcription in multiple model organisms.

Sorveglianza di genoma di errori di trascrizione in organismi eucarioti

Accurate transcription is required for the faithful expression of genetic information. Surprisingly though, little is known about the mechanisms that ...

Producing Gene Deletions in Escherichia coli by P1 Transduction with Excisable Antibiotic Resistance Cassettes

A first approach to study the function of an unknown gene in bacteria is to create a knock-out of this gene. Here, we describe a robust and fast protocol for transferring gene deletion mutations from one Escherichia coli strain to another by using generalized transduction with the bacteriophage P1. This method requires that the mutation be selectable (e.g., based on gene disruptions using antibiotic cassette insertions). Such antibiotic cassettes can be mobilized from a donor strain and introduced into a recipient strain of interest to quickly and easily generate a gene deletion mutant. The antibiotic cassette can be designed to include flippase recognition sites that allow the excision of the cassette by a site-specific recombinase to produce a clean knock-out with only a ~100-base-pair-long scar sequence in the genome. We demonstrate the protocol by knocking out the tamA gene encoding an assembly factor involved in autotransporter biogenesis and test the effect of this knock-out on the biogenesis and function of two trimeric autotransporter adhesins. Though gene deletion by P1 transduction has its limitations, the ease and speed of its implementation make it an attractive alternative to other methods of gene deletion.

Producing Gene Deletions in Escherichia coli by P1 Transduction with Excisable Antibiotic Resistance Cassettes

Here we present a protocol for the use of pre-existing antibiotic resistance-cassette deletion constructs as a basis for making deletion mutants in other E. coli strains. Such deletion mutations can be mobilized and inserted into the corresponding locus of a recipient strain using P1 bacteriophage transduction.

Produzione di delezioni del Gene in Escherichia coli di trasduzione P1 con cassette di resistenza agli antibiotici soggetti ad accisa

A first approach to study the function of an unknown gene in bacteria is to create a knock-out of this gene. Here, we describe a robust and fast protocol ...

qKAT: Quantitative Semi-automated Typing of Killer-cell Immunoglobulin-like Receptor Genes

Killer cell immunoglobulin-like receptors (KIRs) are a set of inhibitory and activating immune receptors, on natural killer (NK) and T cells, encoded by a polymorphic cluster of genes on chromosome 19. Their best-characterized ligands are the human leukocyte antigen (HLA) molecules that are encoded within the major histocompatibility complex (MHC) locus on chromosome 6. There is substantial evidence that they play a significant role in immunity, reproduction, and transplantation, making it crucial to have techniques that can accurately genotype them. However, high-sequence homology, as well as allelic and copy number variation, make it difficult to design methods that can accurately and efficiently genotype all KIR genes. Traditional methods are usually limited in the resolution of data obtained, throughput, cost-effectiveness, and the time taken for setting up and running the experiments. We describe a method called quantitative KIR semi-automated typing (qKAT), which is a high-throughput multiplex real-time polymerase chain reaction method that can determine the gene copy numbers for all genes in the KIR locus. qKAT is a simple high-throughput method that can provide high-resolution KIR copy number data, which can be further used to infer the variations in the structurally polymorphic haplotypes that encompass them. This copy number and haplotype data can be beneficial for studies on large-scale disease associations, population genetics, as well as investigations on expression and functional interactions between KIR and HLA.

Quantitative killer cell immunoglobulin-like receptor (KIR) semi-automated typing (qKAT) is a simple, high-throughput, and cost-effective method to copy number type KIR genes for their application in population and disease association studies.

qKAT: Quantitative sulla tipizzazione di assassino-cellula immunoglobulina-come geni del ricevitore

Killer cell immunoglobulin-like receptors (KIRs) are a set of inhibitory and activating immune receptors, on natural killer (NK) and T cells, encoded by a ...

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other important cellular biology questions. The technologies available to genetically manipulate Dictyostelium cells are well-developed. Transfections can be performed using different selectable markers and marker re-cycling, including homologous recombination and insertional mutagenesis. This is supported by a well-annotated genome. However, these approaches are optimized for axenic cell lines growing in liquid cultures and are difficult to apply to non-axenic wild-type cells, which feed only on bacteria. The mutations that are present in axenic strains disturb Ras signaling, causing excessive macropinocytosis required for feeding, and impair cell migration, which confounds the interpretation of signal transduction and chemotaxis experiments in those strains. Earlier attempts to genetically manipulate non-axenic cells have lacked efficiency and required complex experimental procedures. We have developed a simple transfection protocol that, for the first time, overcomes these limitations. Those series of large improvements to Dictyostelium molecular genetics allow wild-type cells to be manipulated as easily as standard laboratory strains. In addition to the advantages for studying uncorrupted signaling and motility processes, mutants that disrupt macropinocytosis-based growth can now be readily isolated. Furthermore, the entire transfection workflow is greatly accelerated, with recombinant cells that can be generated in days rather than weeks. Another advantage is that molecular genetics can further be performed with freshly isolated wild-type Dictyostelium samples from the environment. This can help to extend the scope of approaches used in these research areas.

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is a popular model organism to study complex cellular processes such as cell migration, endocytosis, and development. The utility of the organism is dependent on the feasibility of genetic manipulation. Here, we present methods to transfect Dictyostelium discoideum cells that overcome existing limitations of culturing cells in liquid media.

Ingegneria genetica di Dictyostelium discoideum cellule basata sulla selezione e crescita sui batteri

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other ...

Designing Automated, High-throughput, Continuous Cell Growth Experiments Using eVOLVER

Continuous culture methods enable cells to be grown under quantitatively controlled environmental conditions, and are thus broadly useful for measuring fitness phenotypes and improving our understanding of how genotypes are shaped by selection. Extensive recent efforts to develop and apply niche continuous culture devices have revealed the benefits of conducting new forms of cell culture control. This includes defining custom selection pressures and increasing throughput for studies ranging from long-term experimental evolution to genome-wide library selections and synthetic gene circuit characterization. The eVOLVER platform was recently developed to meet this growing demand: a continuous culture platform with a high degree of scalability, flexibility, and automation. eVOLVER provides a single standardizing platform that can be (re)-configured and scaled with minimal effort to perform many different types of high-throughput or multi-dimensional growth selection experiments. Here, a protocol is presented to provide users of the eVOLVER framework a description for configuring the system to conduct a custom, large-scale continuous growth experiment. Specifically, the protocol guides users on how to program the system to multiplex two selection pressures &#8212; temperature and osmolarity &#8212; across many eVOLVER vials in order to quantify fitness landscapes of Saccharomyces cerevisiae mutants at fine resolution. We show how the device can be configured both programmatically, through its open-source web-based software, and physically, by arranging fluidic and hardware layouts. The process of physically setting up the device, programming the culture routine, monitoring and interacting with the experiment in real-time over the internet, sampling vials for subsequent offline analysis, and post experiment data analysis are detailed. This should serve as a starting point for researchers across diverse disciplines to apply eVOLVER in the design of their own complex and high-throughput cell growth experiments to study and manipulate biological systems.

The eVOLVER framework enables high-throughput continuous microbial culture with high resolution and dynamic control over experimental parameters. This protocol demonstrates how to apply the system to conduct a complex fitness experiment, guiding users on programming automated control over many individual cultures, measuring, collecting, and interacting with experimental data in real-time.

Progettare esperimenti di crescita cellulare automatizzati, ad alta produttività e continui utilizzando eVOLVER

Continuous culture methods enable cells to be grown under quantitatively controlled environmental conditions, and are thus broadly useful for measuring ...

Use of Frozen Tissue in the Comet Assay for the Evaluation of DNA Damage

The comet assay is gaining popularity as a means to assess DNA damage in cultured cells and tissues, particularly following exposure to chemicals or other environmental stressors. Use of the comet assay in regulatory testing for genotoxic potential in rodents has been driven by adoption of an Organisation for Economic Co-operation and Development (OECD) test guideline in 2014. Comet assay slides are typically prepared from fresh tissue at the time of necropsy; however, freezing tissue samples can avoid logistical challenges associated with simultaneous preparation of slides from multiple organs per animal and from many animals per study. Freezing also enables shipping samples from the exposure facility to a different laboratory for analysis, and storage of frozen tissue facilitates deferring a decision to generate DNA damage data for a given organ. The alkaline comet assay is useful for detecting exposure-related DNA double- and single-strand breaks, alkali-labile lesions, and strand breaks associated with incomplete DNA excision repair. However, DNA damage can also result from mechanical shearing or improper sample processing procedures, confounding the results of the assay. Reproducibility in collection and processing of tissue samples during necropsies may be difficult to control due to fluctuating laboratory personnel with varying levels of experience in harvesting tissues for the comet assay. Enhancing consistency through refresher training or deployment of mobile units staffed with experienced laboratory personnel is costly and may not always be feasible. To optimize consistent generation of high quality samples for comet assay analysis, a method for homogenizing flash frozen cubes of tissue using a customized tissue mincing device was evaluated. Samples prepared for the comet assay by this method compared favorably in quality to fresh and frozen tissue samples prepared by mincing during necropsy. Moreover, low baseline DNA damage was measured in cells from frozen cubes of tissue following prolonged storage.

This protocol describes several procedures for preparing high quality frozen tissue samples at the time of necropsy for use in the comet assay to assess DNA damage: 1) minced tissue, 2) scraped epithelial cells from the gastrointestinal tract, and 3) cubed tissue samples, requiring homogenization using a tissue mincing device.

Uso di tessuto congelato nel saggio Cometa per la valutazione del danno del DNA

The comet assay is gaining popularity as a means to assess DNA damage in cultured cells and tissues, particularly following exposure to chemicals or other ...

Use of Drosophila S2 Cells for Live Imaging of Cell Division

Drosophila S2 cells are an important tool in studying mitosis in tissue culture, providing molecular insights into this fundamental cellular process in a rapid and high-throughput manner. S2 cells have proven amenable to both fixed- and live-cell imaging applications. Notably, live-cell imaging can yield valuable information about how loss or knockdown of a gene can affect the kinetics and dynamics of key events during cell division, including mitotic spindle assembly, chromosome congression, and segregation, as well as overall cell cycle timing. Here we utilize S2 cells stably transfected with fluorescently tagged mCherry:&#945;-tubulin to mark the mitotic spindle and GFP:CENP-A (referred to as &#8216;CID&#8217; gene in Drosophila) to mark the centromere to analyze the effects of key mitotic genes on the timing of cell divisions, from prophase (specifically at Nuclear Envelope Breakdown; NEBD) to the onset of anaphase. This imaging protocol also allows for the visualization of the spindle microtubule and chromosome dynamics throughout mitosis. Herein, we aim to provide a simple yet comprehensive protocol that will allow readers to easily adapt S2 cells for live imaging experiments. Results obtained from such experiments should expand our understanding of genes involved in the cell division by defining their role in several simultaneous and dynamic events. Observations made in this cell culture system can be validated and further investigated in vivo using the impressive toolkit of genetic approaches in flies.

Use of Drosophila S2 Cells for Live Imaging of Cell Division

Cell divisions can be visualized in real time using fluorescently tagged proteins and time-lapse microscopy. Using the protocol presented here, users can analyze cell division timing dynamics, mitotic spindle assembly, and chromosome congression and segregation. Defects in these events following RNA interference (RNAi)-mediated gene knockdown can be assessed and quantified.

Uso di celle Drosophila S2 per l'imaging live della divisione cellulare

Drosophila S2 cells are an important tool in studying mitosis in tissue culture, providing molecular insights into this fundamental cellular process in a ...

A FACS-based Protocol to Isolate RNA from the Secondary Cells of Drosophila Male Accessory Glands

To understand the function of an organ, it is often useful to understand the role of its constituent cell populations. Unfortunately, the rarity of individual cell populations often makes it difficult to obtain enough material for molecular studies. For example, the accessory gland of the Drosophila male reproductive system contains two distinct secretory cell types. The main cells make up 96% of the secretory cells of the gland, while the secondary cells (SC) make up the remaining 4% of cells (about 80 cells per male). Although both cell types produce important components of the seminal fluid, only a few genes are known to be specific to the SCs. The rarity of SCs has, thus far, hindered transcriptomic analysis study of this important cell type. Here, a method is presented that allows for the purification of SCs for RNA extraction and sequencing. The protocol consists in first dissecting glands from flies expressing a SC-specific GFP reporter and then subjecting these glands to protease digestion and mechanical dissociation to obtain individual cells. Following these steps, individual, living, GFP-marked cells are sorted using a fluorescent activated cell sorter (FACS) for RNA purification. This procedure yields SC-specific RNAs from ~40 males per condition for downstream RT-qPCR and/or RNA sequencing in the course of one day. The rapidity and simplicity of the procedure allows for the transcriptomes of many different flies, from different genotypes or environmental conditions, to be determined in a short period of time.

A FACS-based Protocol to Isolate RNA from the Secondary Cells of Drosophila Male Accessory Glands

Here, we present a protocol to dissociate and sort a specific cell population from the Drosophila male accessory glands (secondary cells) for RNA sequencing and RT-qPCR. Cell isolation is accomplished through FACS purification of GFP-expressing secondary cells after a multistep-dissociation process requiring dissection, proteases digestion and mechanical dispersion.

Un protocollo basato su FACS per isolare l'RNA dalle cellule secondarie delle ghiandole accessorie maschili della Drosophila

To understand the function of an organ, it is often useful to understand the role of its constituent cell populations. Unfortunately, the rarity of ...

Progettazione e l'uso di un basso costo, Automated Morbidostat per Adaptive Evolution di batteri sotto antibiotici selezione dei farmaci

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Procedura per l'Adaptive Laboratorio evoluzione dei microrganismi Utilizzando un chemostat