We are grateful to the Pacific Northwest National Laboratory (PNNL) Earth and Biological Sciences (EBD) mission seed Laboratory Directed Research and Development (LDRD) fund for support. Instrumental access was provided through a W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL) General User Proposal. EMSL is a national scientific user facility sponsored by the Office of Biological and Environmental Research (BER) at PNNL. The authors thank Dr. Yuanzhao Ding for proof reading the manuscript and providing useful feedback. PNNL is operated by Battelle for the DOE under Contract DE-AC05-76RL01830.

1. Preparation of Materials
<ol>
	<li>Preparation of Medium Tubing
	<ol>
		<li>Serum Bottles (one needed per biofilm culture and three needed per growth curve) 
		Note: As mentioned in the introduction, any growth medium suitable to provide the nutrients needed for the strain of bacteria of interest can be utilized for this procedure; in this case, &#34;nanowires&#34; media and TSB without dextrose medium was used for the growth of S. oneidensis MR-1 GFP.13
		<ol>
...

<ol>
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C., Wingender, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biofilm+matrix.">The biofilm matrix.</a> Nat Rev Microbiol. 8 (9), 623-633 (2010).</li><li>Aldeek, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterned+hydrophobic+domains+in+the+exopolymer+matrix+of+Shewanella+oneidensis+MR-1+biofilms.">Patterned hydrophobic domains in the exopolymer matrix of Shewanella oneidensis MR-1 biofilms.</a> Appl Environ Microbiol. 79 (4), 1400-1402 (2013).</li><li>Hua, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+molecular+imaging+of+a+hydrated+biofilm+in+a+microfluidic+reactor+by+ToF-SIMS.">In situ molecular imaging of a hydrated biofilm in a microfluidic reactor by ToF-SIMS.</a> Analyst. 139 (7), 1609-1613 (2014).</li><li>Yu, X. Y., Yang, L., Cowin, J. P., Iedema, M., Zhu, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systems+and+methods+for+analyzing+liquids+under+vacuum.">Systems and methods for analyzing liquids under vacuum.</a> US Patent. , (2013).</li><li>Yu, X. Y., Liu, B., Yang, L., Zhu, Z., Marshall, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+electrochemical+device+and+process+for+chemical+imaging+and+electrochemical+analysis+at+the+electrode-liquid+interface+in+situ.">Microfluidic electrochemical device and process for chemical imaging and electrochemical analysis at the electrode-liquid interface in situ.</a> US Patent. , (2014).</li><li>Yang, L., Yu, X. Y., Zhu, Z. H., Thevuthasan, T., Cowin, J. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+liquid+surfaces+under+vacuum+using+SEM+and+ToF-SIMS.">Probing liquid surfaces under vacuum using SEM and ToF-SIMS.</a> Lab Chip. 11 (15), 2481-2484 (2011).</li><li>Ding, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Situ+Molecular+Imaging+of+the+Biofilm+and+Its+Matrix.">In Situ Molecular Imaging of the Biofilm and Its Matrix.</a> Anal Chem. , (2016).</li><li>Yang, J., Ghobadian, S., Montazami, R., Hashemi, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Proceedings of the Asme 11th Fuel Cell Science, Engineering, and Technology Conference, 2013. , (2013).</li><li>Yu, F., Wang, C. X., Ma, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+Graphene-Modified+Electrodes+in+Microbial+Fuel+Cells.">Applications of Graphene-Modified Electrodes in Microbial Fuel Cells.</a> Materials. 9 (10), (2016).</li><li>Yu, J., Zhou, Y., Hua, X., Zhu, Z., Yu, X. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Situ+Characterization+of+Hydrated+Proteins+in+Water+by+SALVI+and+ToF-SIMS.">In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS.</a> J Vis Exp. (108), e53708 (2016).</li><li>Hill, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Effects of Electron-Transport-System Impairment on Hydrogen Gas Production by the Bacterium Shewanella oneidensis MR-1. , (2007).</li><li>McCormick, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biophotovoltaics:+oxygenic+photosynthetic+organisms+in+the+world+of+bioelectrochemical+systems.">Biophotovoltaics: oxygenic photosynthetic organisms in the world of bioelectrochemical systems.</a> Energy Environ Sci. 8 (4), 1092-1109 (2015).</li><li>Liu, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+chemical+probing+of+the+electrode-electrolyte+interface+by+ToF-SIMS.">In situ chemical probing of the electrode-electrolyte interface by ToF-SIMS.</a> Lab Chip. 14, 855-859 (2014).</li><li>Keune, K., Hoogland, F., Boon, J. J., Peggie, D., Higgitt, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+"added+value"+of+SIMS:+A+mass+spectrometric+and+spectroscopic+study+of+an+unusual+Naples+yellow+oil+paint+reconstruction.">Evaluation of the "added value" of SIMS: A mass spectrometric and spectroscopic study of an unusual Naples yellow oil paint reconstruction.</a> Int J mass Spectrom. 284 (1-3), 22-34 (2009).</li><li>Lee, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Mass Spectrometry Handbook. , 988 (2012).</li><li>Petrovic, M., Barcelo, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+anionic+and+nonionic+surfactants,+their+degradation+products,+and+endocrine-disrupting+compounds+in+sewage+sludge+by+liquid+chromatography/mass+spectrometry.">Determination of anionic and nonionic surfactants, their degradation products, and endocrine-disrupting compounds in sewage sludge by liquid chromatography/mass spectrometry.</a> Anal Chem. 72 (19), 4560-4567 (2000).</li><li>Vickerman, J. 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The authors have nothing to disclose.

After inoculating at log-phase, it is important to test the number of days and temperature at which the biofilm should grow before it is healthy and thick enough for imaging, as described in step 3.1. This procedure specifically covers culturing a S. oneidensis MR1 biofilm at room temperature; however different room temperatures can influence the rate of growth. Therefore, it is critical to use optical imaging to understand whether the biofilm is ready before proceeding to ToF-SIMS analysis. Similarly, different strains ...

Bacterial biofilms are surface-associated communities which have evolved over time as a defense for bacteria to survive varying adverse physical and mechanical stimuli, wherein cells are able to attach and survive in many possible environments.1,2 Biofilms are vastly investigated and have applications in many fields such as biomedicine, biomedical engineering, agriculture, and industrial research and development.1,2 Understanding the chemical mapping of these complex microbial communities, including their self-produced extracellular polymeric substances (EPS) and their local water-cluster environment, is essential to gaining an accurate and detailed depiction of their biological activities.2
Biofilms exist and grow within a highly hydrated state. This presents a great challenge in using vacuum-based surface analysis techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) due to the difficulty in studying volatile liquids in vacuum. As a result, vacuum-based surface analysis techniques have been limited almost exclusively to studying biofilm samples at only their dried state. However, studying a biofilm in its dried state inhibits the accurate investigation of its true biological microenvironment. It often causes drastic changes to the EPS integrity and biofilm morphology, which has been demonstrated after comparing dry biofilm mass spectral results to in situ liquid studies.3,4 This article presents a solution for studying biofilms within their natural hydrated state by employing the use of our System for Analysis at the Liquid Vacuum Interface (SALVI),5,6 a microfluidic reactor that contains liquid under its thin silicon nitride (SiN) membrane in a microchannel made of polydimethylsiloxane (PMDS), thus providing direct access to the secondary ion probe beam while still maintaining the structural integrity of the liquid matrix within a vacuum chamber.7,8
S. oneidensis MR-1 mutated to express green fluorescence protein (GFP) was chosen as a model organism for this biofilm procedure illustration due to its metabolic versatility and common use in environmental and applied microbiology, which was based heavily on its unique capability for metal reduction and extracellular electron transfer.9,10,11 Additionally, the presence of GFP allowed for easy continuous biofilm-thickness monitoring through fluorescence microscopy, using a fluorescein isothiocyanate (FITC) filter. Our previous studies have shown evidence of this bacteria favoring attachment to the SiN window using in operando fluorescence imaging for biofilm growth to a thickness of up to one hundred micrometers.4,12 While this paper will only discuss the confirmation of biofilm&#39;s presence through fluorescence microscopy, the SALVI is compatible with other optical imaging methods such as super-resolution fluorescence imaging (i.e., structured illumination microscopy (SIM)9) and confocal laser scanning microscopy (CLSM) imaging4). Optical imaging can serve to measure the biofilm thickness, and obtain a 3D image of, the shape of the biofilm as it appears, confirming its thickness and its attachment to the SiN window.9 While GFP was used in the SIMS analysis, S. oneidensis without GFP was used for the growth curve, as this only required measurement of optical density and did not require any fluorescent imaging. Generally, the difference between the GFP tagged and untagged species in the growth curve is insignificant. Additionally, while this protocol uses S. oneidensis MR-1 GFP as a model organism to describe the procedure, this procedure is designed for any bacterial strain that may be needed for cultivation within SALVI. Although, given knowledge of the bacterial strain needed, some growth conditions such as time, temperature, and oxygen environment may need to be modified to accommodate the strain of bacteria to be used. For growth medium, this procedure uses &#34;nanowires&#34; medium, tryptic soy broth (TSB) without dextrose, and tryptic soy agar (TSA) without dextrose for culturing. The composition of &#34;nanowires&#34; medium has been specially formulated for the growth and for monitoring of extensions of the membrane and periplasm of S. oneidensis that appear to take the shape of small wires, and the medium composition has been established within previous research.13,14
Our previous protocol on in situ liquid ToF-SIMS has illustrated the benefit that SALVI has to offer for protein immobilization and attachment to the SiN, as well as a detailed protocol on ToF-SIMS analysis and data reduction.12 Rather than reiterate data reduction steps, this paper will serve to instead focus on the unique approach of setting up and cultivating biofilms within our SALVI microchannel, as well as the imaging steps to detect biofilm presence and thickness prior to ToF-SIMS analysis. While biofilms have been previously limited to only dried samples within the chamber of vacuum-based surface analytical techniques, detailed EPS and biofilm chemical mapping of live biofilms can now be obtained in situ because of this new capability.

<table width="2446">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">ToF-SIMS</td>
			<td style="width:260px;">IONTOF</td>
			<td style="width:123px;">TOF.SIMS 5</td>
			<td style="width:1675px;">Resolution:&#62;10,000 m/&#916;m for mass resolution;&#62;4,000 m/&#916;m for high spatial resolution</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">System for Analysis at the Liquid Vacuum Interface (SALVI)</td>
			<td style="width:260px;">Pacific Northwest National Laboratory</td>
			<td style="width:123px;">N/A</td>
			<td>SALVI is a unique, self-contained, portable analytical tool that, for the first time, enables vacuum based scientific instruments such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze liquid surfaces in their natural state at the molecular level.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">-80&#176;C Freezer</td>
			<td style="width:260px;">New Brunswick Scientific</td>
			<td style="width:123px;">N/A</td>
			<td>U410 Premium Energy Efficient Ultra-Low Temperature Freezer</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">4&#176;C Refrigerator</td>
			<td style="width:260px;">BioCold Scientific</td>
			<td style="width:123px;">N/A</td>
			<td>COLDBOX1</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Orbital Shaker</td>
			<td style="width:260px;">New Brunswick Scientific</td>
			<td style="width:123px;">N/A</td>
			<td style="width:1675px;">Innova 4900 Multi-Tier Environmental Shaker, set at 30 degrees Celsius for serum bottle and flask culturing, set at 150rpm.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Syringe Pump</td>
			<td style="width:260px;">Cole-Parmer</td>
			<td style="width:123px;">EW-74905-02</td>
			<td>Cole-Parmer Syringe Pump, Infusion Only, Touchscreen Control 74905-02, used for injecting liquid into the tubing system and SALVI at a constant flowrate.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Incubator</td>
			<td style="width:260px;">Barnstead International</td>
			<td style="width:123px;">LT1465X3</td>
			<td>Lab-Line incubator, set at 30 degrees Celsius for plate culturing.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Autoclave</td>
			<td style="width:260px;">Getinge</td>
			<td style="width:123px;">533LS</td>
			<td>Used to sterilize PEEK fittings, tubing systems, serum vials, and medium. Model 533LS Vacuum Steam Sterilizer</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Spectrophotometer</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">4001-000</td>
			<td>GENESYS 20 spectrophotometer for OD600 readings of cuvettes for growth curves.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Biological Safety Cabinet</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">1385</td>
			<td>1300 Series AZ Biological Safety Cabinet</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Fluorescence Microscope</td>
			<td style="width:260px;">Nikon</td>
			<td style="width:123px;">N/A</td>
			<td>Nikon OPTIPHOT-2 fluorescence microscope with camera and super high pressure mercury lamp power supply.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">pH Meter</td>
			<td style="width:260px;">Mettler Toledo</td>
			<td style="width:123px;">51302803</td>
			<td>Used to test the pH of the &#8220;nanowires&#8221; medium after finished and before autoclaving.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">PEEK Union</td>
			<td style="width:260px;">Valco</td>
			<td style="width:123px;">ZU1TPK</td>
			<td>For connecting the inlet and outlet of SALVI, the syringe to the tubing system, and the inlet of the SALVI to the drip chamber of the tubing system.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">5 Axes Sample Stage</td>
			<td style="width:260px;">IONTOF</td>
			<td style="width:123px;">N/A</td>
			<td>Stage is self-made for mounting SALVI in ToF-SIMS.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Barnstead Nanopure Water Purification System</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">D11921</td>
			<td>ROpure LP Reverse Osmosis filtration module (D2716)</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Pipette</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">21-377-821</td>
			<td>Range: 100 to 1,000 &#181;L.</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Pipette Tip</td>
			<td style="width:260px;">Neptune</td>
			<td style="width:123px;">2112.96.BS</td>
			<td>1,000 &#181;L pipette tips</td>
		</tr>
		<tr height="20">
			<td height="20" style="width:389px;height:20px;">Razor Blade Handle</td>
			<td style="width:260px;">Stanley</td>
			<td style="width:123px;">N/A</td>
			<td>Stanley Bostitch Razor Blade Scraper with 5 Single-Edge Blades, used for cutting PTFE tubing</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Syringe</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">309659</td>
			<td>1 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Syringe</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">309657</td>
			<td>3 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Syringe</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">309646</td>
			<td>5 mL; Used for making the drip chamber</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Syringe</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">309604</td>
			<td>10 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Syringe</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">302830</td>
			<td>20 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Disposable Pipette</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">13-678-11</td>
			<td>25 mL Fisherbrand&#8482; Sterile Polystyrene Disposable Serological Pipets with Magnifier Stripe, for filling serum bottles.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Electric Pipette Filler</td>
			<td style="width:260px;">Pipet-aid</td>
			<td style="width:123px;">P-57260</td>
			<td>Vacuum pressure electric serological pipette filler</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Serum Bottle</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">33109-U</td>
			<td>Holds approximately 69 mL of liquid for culture growth, optimum for use of 20mL culture per bottle.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Anaerobic Culture Tube</td>
			<td style="width:260px;">VWR</td>
			<td style="width:123px;">89167-178</td>
			<td>Anaerobic Tubes, 18 x 150 mm, Supplied with 20 mm Blue Butyl Rubber Stopper and Aluminum Seal.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Rubber Stopper</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">27235-U</td>
			<td>Silicone stopper, used for sealing serum bottles and for creating the tubing system/drip chamber.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Aluminum Crimp Seal (without septum)</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">27227-U</td>
			<td>Aluminum seal for top of serum bottle for use with serum bottle crimper.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Serum Bottle Aluminum Seal Crimper</td>
			<td style="width:260px;">Wheaton</td>
			<td style="width:123px;">224307</td>
			<td>30 mm crimper with standard seal.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">PTFE Tubing</td>
			<td style="width:260px;">Supelco</td>
			<td style="width:123px;">58697-U</td>
			<td>1.58 mm OD x 0.5 mm ID 50 ft. PTFE Teflon tubing, used for creating the tubing system.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Disposable Cuvettes</td>
			<td style="width:260px;">GMBH</td>
			<td style="width:123px;">759085D</td>
			<td>1.5 Ml for use with spectrophotometer.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Needle</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">303015</td>
			<td>22G; used for serum bottle injection.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Needle</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">305120</td>
			<td>23G; used for punching-through rubber stopper to create drip tubing system.</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Shewanella oneidensis MR-1 with GFP</td>
			<td style="width:260px;">N/A</td>
			<td style="width:123px;">N/A</td>
			<td>Matthysse AG, Stretton S, Dandie C, McClure NC, &#38; Goodman AE (1996) Construction of GFP vectors for use in Gram-negative bacteria other than Escherichia coli. FEMS Microbiol Lett 145(1):87-94.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Ethanol</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">&#160;S25310A</td>
			<td>95% Denatured</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">TSA</td>
			<td style="width:260px;">BD</td>
			<td style="width:123px;">212305</td>
			<td>Tryptic soy agar for culturing the model organism (S. oneidensis) used in this protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">PIPES Buffer</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">P-1851</td>
			<td>Used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Hydroxide</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">S-5881</td>
			<td>Used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Ammonium Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">A-5666</td>
			<td>Used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Potassium Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">P-4504</td>
			<td>Used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Phosphate Monobasic</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">S-9638</td>
			<td>Used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Chloride</td>
			<td style="width:260px;">Thermo Fisher Scientific</td>
			<td style="width:123px;">S271-3</td>
			<td>Used for &#8220;nanowires&#8221; medium, and used to make mineral solution used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium lactate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">L-1375</td>
			<td>60%(w/w) syrup @ 98% pure, d=1.3 g/mL, 7M, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Bicarbonate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">S-5761</td>
			<td>Used to make ferric NTA solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Nitrilotriacetic Acid Trisodium Salt</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">N-0253</td>
			<td>Used to make ferric NTA solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Iron (III) Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">451649</td>
			<td>Used to make ferric NTA solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Magnesium Sulfate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">208094</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Manganese (II) Sulfate Monohydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">M-7634</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Iron(II) Sulfate Heptahydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">215422</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Calcium Chloride Dihydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">223506</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Cobalt(II) Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">60818</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Zinc Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">229997</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Copper(II) Sulfate Pentahydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">C-8027</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Aluminum Potassium Sulfate Dodecahydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">237086</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Boric Acid</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">B-6768</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Molybdate Dihydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">331058</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Nickel(II) Chloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">339350</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Sodium Tungstate Dihydrate</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">14304</td>
			<td>Used to make minerals solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">D-Biotin</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">47868</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Folic Acid</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">F-7876</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Pyridoxine Hydrochloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">P-9755</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Riboflavin (B2)</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">47861</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Thiamine Hydrochloride</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">T-4625</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Nicotinic Acid</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">N4126</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">D-Pantothenic Acid Hemicalcium Salt</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">21210</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Vitamin B12</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">V-2876</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">4-Aminobenzoic Acid</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">A-9878</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:389px;height:21px;">Thioctic Acid</td>
			<td style="width:260px;">Sigma</td>
			<td style="width:123px;">T-1395</td>
			<td>Used to make vitamin solution, used for &#8220;nanowires&#8221; medium {Hill, E.A. 2007}</td>
		</tr>
	</tbody>
</table>

in situ characterization of shewanella oneidensis mr1 biofilms by salvi and tof-sims

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) and their roles in environmental microbiology. This study outlines a method to cultivate biofilm attachment to the System for Analysis at the Liquid Vacuum Interface (SALVI) and achieve in situ chemical mapping of a living biofilm by time-of-flight secondary ion mass spectrometry (ToF-SIMS). This is done through the culturing of bacteria both outside and within the SALVI channel with our specialized setup, as well as through optical imaging techniques to detect the biofilm presence and thickness before ToF-SIMS analysis. Our results show the characteristic peaks of the Shewanella biofilm in its natural hydrated state, highlighting upon its localized water cluster environment, as well as EPS fragments, which are drastically different from the same biofilm's dehydrated state. These results demonstrate the breakthrough capability of SALVI that allows for in situ biofilm imaging with a vacuum-based chemical imaging instrument.

These representative results serve to show how the chemical profile of the attached biofilm can be identified and interpreted, as obtained through ToF-SIMS. After plotting mass spectra from ToF-SIMS data acquisition, highlighted briefly in the procedures section, peak identification should be conducted in order to assign identities to each respective m/z value. This can be done through extensive literature review on mass spectrometry on bacteria and specific chemical fragments that are ex...

Watch this Scientific Journal Video about In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS at JoVE.com

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

This article presents a method for growing a biofilm for in situ time-of-flight secondary ion mass spectrometry for chemical mapping in its hydrated state, enabled by a microfluidic reactor, System for Analysis at the liquid Vacuum Interface. The Shewanella oneidensis MR-1 with green fluorescence protein was used as a model.

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) ...

The overall goal of this procedure is to culture bacteria in the system for analysis at the liquid vacuum interface, or SALVI, for subsequent imagining of the biofilms in their natural hydrated state with vacuum-based techniques such as Time-of-Flight Secondary Ion Mass Spectrometry. We present a method that helps answer key questions in environmental microbiology by visualizing the chemical-spatial distribution of living biofilms using imaging mass spectrometry like SIMS. The main advantage of this technique is that we can introduce biofilms alive to a mass spectrometer and many other analytical platforms to obtain multiplex measurements.Although Shewanella oneidensis is used in this video, this method can also be applied to anaerobic chambers for biofilm growth. The latter requires a more stringent growth environment. Visual demonstration of this method is critical as the tubing setup steps are difficult to learn.Specific placement of tubing and care are necessary when transferring to the biosafety cabinet. Using a 22 gauge needle, carefully punch a hole through a serum bottle rubber stopper. Cut 20 inches of 1/32 inch PTFE tubing with a razor, such that one end of the tubing is pointed.Using the pointed end, thread the PTFE tubing through the hole in the top portion of the rubber stopper. Push the tube through until roughly two centimeters is through the stopper and cut the pointed end of the PTFE tube with a razor to have a flat end. Remove the plunger of a five milliliter syringe and fit the rubber stopper into the open end of the syringe.The two centimeter end of PTFE tubing is within the barrel of the syringe. This is the bubble trap. Wrap the bubble trap with aluminum foil and secure it with autoclave tape.Then autoclave the foil package to sterilize the tubing with a gravity cycle at 121 degrees celsius for 30 minutes. Store the sealed foil package at room temperature until it is ready for use. This procedure specifically covers culturing a Shewanella oneidensis MR-1 biofilm at room temperature after 24 hours of incubation.However, different strains of bacteria require different growth conditions and lengths to achieve a desirable thickness for analysis. The SALVI tubing system is made up of the syringe containing the liquid reservoir, which is attached with a PEEK injector to the PTFE tubing. This is attached to the drip chamber, which has a PEEK injector fitting attached to the SALVI inlet tubing.The drip chamber is also attached to the outlet container that the SALVI outlet tubing is sealed to. To promote sterility of the tubing system, detach the syringe from the syringe pump by unscrewing the metal syringe holder. Then bring the syringe with the attached tubing to a sterile biological safety cabinet.Use a new SALVI device and attach a PEEk fitting and injector to one end of a PTFE tubing. SALVI devices are prepared fresh for each experiment following the device fabrication, which is detailed in previous research and patents. Next, aspirate two milliliters of 70%ethanol and deionized water into a syringe and connect the syringe to the PEEK fitting on the SALVI.After connecting the syringe to a syringe pump and attaching the outlet of the SALVI to a waste bottle, allow the ethanol solution to run through the SALVI at 20 microliters per minute for one and a half hours. Then aspirate four milliliters of sterilized deionized water into a syringe and connect it to the inlet of the same SALVI. After connecting the syringe to a syringe pump, allow the water to run through the SALVI at 20 microliters per minute for at least three hours.Within a biosafety cabinet, open the prepared foil packet and connect a sterile PEEK injector and fittings to the end of the PTFE tubing. Aspirate approximately three milliliters of sterile medium into a syringe and attach it to the PTFE tube. Invert the five milliliter drip chamber and using a sterile syringe inject the growth medium into the drip chamber until it reaches a total volume of one milliliter.Next, connect the end of the five milliliter syringe drip chamber to the inlet of the SALVI. Aspirate 10 milliliters of growth medium into a sterile syringe and connect it to the inlet of the drip tubing. Allow the drip tubing to be vertical.The syringe pump should be placed on an elevated surface with drip tubing secured by tape and with the SALVI secured on a flat surface below. Cover the outlet bottle with foil or plastic paraffin film to minimize the probability of medium contamination. Allow the medium to run through the SAVLI at 20 microliters per minute for 12 hours.This ensures that all traces of ethanol have been removed from the microchannel and tubing of the SALVI before inoculating with bacteria. For added protection, keep the SALVI microchannel chamber within a sterilized petri dish with the sides cut to fit the inlet and outlet tubing. Additionally, keep tape always on the window to protect the silicone nitride membrane and channel prior to image analysis.We move the whole tubing system from the syringe pump to bring it to a sterilized biosafety cabinet. Additionally, remove the serum bottle from the incubator that has been inoculated as described in the text protocol. Clean the surface of the serum bottle stopper with 70%ethanol to prevent any contamination.Then use a sterile syringe with an attached sterile 22 gauge needle to extract four milliliters of bacteria from the bottle. Detach the SALVI from the five milliliter chamber of the drip tubing and connect the syringe with inoculated medium directly to the inlet of the SALVI. Leave the drip tubing within the sterile aluminum foil packet or within the biosafety cabinet.Attach the syringe with the SALVI and outlet bottle to the syringe pump. Run at 20 microliters per minute for three hours to inoculate the channel of the SALVI and allow for a multiple volume changes of the liquid contained within the SALVI. Following inoculation, disconnect the syringe with the SALVI from the syringe pump and bring it to the biosafety cabinet.Attach the inlet of the SALVI back to the five milliliter drip chamber. Then aspirate 20 milliliters of growth medium into a sterile syringe and attach it to the inlet of the drip tubing. The flow rate should never be increased or decreased, as changing the flow rate would create sheer stress within the channel and detach the biofilm.To avoid flow rate changes ensure there are no bubbles in the tubing the day before SIMS. It is important to be cautious of bubbles within the bottom of the five milliliter drip tubing where it connects to the SALVI tubing. Fresh medium can be injected into the end of the PEEK injector to ensure that no air will be forced into the SALVI.Bring the tubing attached to the SALVI from the biosafety cabinet to the syringe pump. Allow the medium to pass through the tubing at at rate of two microliters per minute for six to ten days. Refill the SALVI with fresh medium as it runs out within the biosafety cabinet by attaching a new sterile syringe filled with 10 milliliters of growth medium to the SALVI.Using light microscopy or confocal fluorescence imaging, the presence of a biofilm can be detected on the window of the SALVI. Shown here is the negative mass spectrum of a hydrated Shewanella oneidensis MR-1 biofilm within the microfluidic channel. It's obtained by NC2 liquid Time-of-Flight Secondary Ion Mass Spectrometry.The deionized water spectrum is also shown. A comparison of 2-D images of peaks of interest in the MR-1 biofilm to deionized water are shown. Once interesting m over z values can be identified from studying the mass spectra potential peak identification is performed through the software library, in lab reference spectra, and a literature survey.Once mastered, this technique takes three days to set up, in addition to the specific time required for the biofilm to grow within the microchannel, which is about five to six days at room temperature for Shewanella. After watching this video, you should have a good understanding of how to grow insatiable biofilms in SALVI devices. Generally, individuals new to this method will struggle because bubbles may form within the growth medium due to bacteria growth.It is necessary to get rid of bubbles before the SIMS analysis. While attempting this procedure, it's important to remember to never change the flow rate after inoculation of bacteria is completed. Even in fluorofil dying steps before optical imaging.Following this procedure, other methods like confocal fluorescence imaging can be performed in order to answer additional questions, like how thick the biofilm was at the time the SIMS took place. After it's development, the technique paved the way for researchers in analytical chemistry and microbiology to explore the chemical profiles of biofilms in their naturally hydrated states.

in-situ-characterization-shewanella-oneidensis-mr1-biofilms-salvi-tof

Research

JoVE Journal

Chemistry

8.9K Views.  Pacific Northwest National Laboratory. The overall goal of this procedure is to culture bacteria in the system for analysis at the liquid vacuum interface, or SALVI, for subsequent imagining of the biofilms in their natural hydrated state with vacuum-based techniques such as Time-of-Flight Secondary Ion Mass Spectrometry. We present a method that helps answer key questions in environmental microbiology by visualizing the chemical-spatial distribution of living biofilms using imaging mass spectrometry like SIMS. The main advantage ...