This work has been supported by Elizabeth E. Kennedy Research Award.

1. إعداد منتج سلالة <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> خط سلالة المكورات الرئوية لفحصها لإنتاج مبيد جرثومي على 5٪ الأغنام الدم الصويا زيتية لوحة أجار من -80 ° C الأسهم الفريزر. ملاحظة: استخدام لوحات الدم للنمو الأولي من سلالة لفحصها لتثبيط يزيد كثيرا من استنساخ للمقايسة. بالإضافة إلى ذلك، وغيرها من السلالات غير الرئوية التي تنتج bacteriocins يمكن استخدامها على الرغم من أن قد تحتاج إلى تعديل لكائن معين ظروف النمو. وقد استخدمنا العقدية الهينة وLactococcus اللبنية في مقايسة تراكب بنجاح. </li><li style=";text-align:right;direction:rtl"> احتضان لوحة بين عشية وضحاها (O / N) عند 37 درجة مئوية مع 5٪ CO 2. </li><li style=";text-align:right;direction:rtl"> بعد مرور فترة الحضانة من سلالة منتج، وإعداد زيتية أجار الصويا (TSA) لوحة من قبل pipetting 3،000 إلى 4،000 وحدة من الكاتلاز على لوحات تحتوي على 25 مل من TSA ونشر الحل الكاتلاز باستخدام الخرز الزجاجي معقمة. السماح لوحة جافة لمدة 10 دقيقة تحتخزانة السلامة البيولوجية. </li><li style=";text-align:right;direction:rtl"> جمع كمية مرئية من البكتيريا على طرف ماصة. طعن غيض ماصة في لوحة TSA المجففة. ملاحظة: أكثر من سلالة واحدة منتج ويمكن طعن في لوحة واحدة TSA. من المهم أن الفضاء خارج طعنات بحيث الناتجة هالات لا تتداخل. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إذا كان ذلك ممكنا، وتشمل يعرف مبيد جرثومي منتج كعنصر تحكم إيجابية والسلالة لاستخدامها في تراكب كعنصر تحكم السلبية. ملاحظة: الضوابط الإيجابية والسلبية هي تم نشرها سابقا ومتاحة عند الطلب 10. </li></ol></li><li style=";text-align:right;direction:rtl"> احتضان TSA وحة تحتوي طعنات متعددة في 37 درجة مئوية مع 5٪ CO 2 لمدة 6 ساعة. </li></ol> 2. جعل الأسهم الجلسرين من سلالة تراكب <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إعداد مخزونات الجلسرين (ثقافات نمت إلى مرحلة منتصف الأسي ثم تخزينها في -80 درجة مئوية بعد إضافة الجلسرين) قبل يوم من الفحص تراكب. تطعيم 5-10 مستعمرات شارع المكورات الرئويةعين لفحصها للحساسية أو إفراز فرمون تود هيويت في المتوسط ​​0.5٪ مع مستخلص الخميرة (THY). ملاحظة: بناء BlpC صحفيين محرض وقد وصفت سابقا 2 و هم سلالات متاحة عند الطلب. </li><li style=";text-align:right;direction:rtl"> احتضان 5-10 المستعمرات في أنابيب زجاجية مع 5 مل من THY مع الأغطية مغلقة بإحكام في 37 ° C حمام الماء دون أن تهتز. </li><li style=";text-align:right;direction:rtl"> احتضان الثقافات في 37 درجة مئوية حتى التوصل الى OD 620 من 0،3-0،5. ملاحظة: هذا سوف يستغرق حوالي 4-5 ساعة اعتمادا على السلالة المستخدمة. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> عكس بلطف الأنبوب عدة مرات قبل قياس OD. </li></ol></li><li style=";text-align:right;direction:rtl"> إذا كانت التجربة لا يمكن أن يؤديها في نفس اليوم أو سيتم استخدام سلالة عدة مرات في المستقبل، وجعل الأسهم الجلسرين واستئناف التجربة في وقت لاحق. للأسهم الجلسرين، إضافة الجلسرين على الثقافات إلى تركيز النهائي من 20٪. الثقافات قسامة إلى 1.5 مل أنابيب microcentrifuge وتخزينها في -80 درجة مئوية. ملاحظة: يمكن أن تكون عينات قtored لشهور في -80 درجة مئوية. إن لم يكن جعل الأسهم الجلسرين، واستخدام عينات للفحص مباشرة تراكب. </li></ol> 3. تراكب الفحص <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> قبيل تراكب التطبيق، خلط مكونات تراكب. في 15 مل أنبوب مخروطي الشكل، إضافة 5 مل من THY، 3،000-4،000 U من الكاتلاز، و 200 ميكرولتر من ثقافة مرق سلالة تراكب التي كانت إما نمت ذلك اليوم أو الأسهم الجلسرين من الثقافة التي تم إذابة في درجة حرارة الغرفة. إذا باستخدام سلالة المراسل، إضافة 50 ميكرولتر من X-غال (40 ملغ / مل) إلى الخليط تراكب. استخدام أنبوب مخروطي واحد لكل لوحة. </li><li style=";text-align:right;direction:rtl"> تتوازن مزيج تراكب في درجة حرارة الغرفة قبل إضافة المنصهر TSA. </li><li style=";text-align:right;direction:rtl"> إزالة لوحة TSA مع سلالة طعن من الحاضنة. تذوب الصلبة TSA في الميكروويف والحفاظ في 55 ° C حمام الماء حتى جاهزة للاستخدام. إضافة 3 مل من المنصهر TSA مع 1.5٪ أجار تبرد إلى 55 درجة مئوية إلى تراكب الخليط. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إعداد مزيج تراكب مباشرة قبل pipetting ل، ستبدأ الخليط إلى ترسيخ جدابسرعة. ملاحظة: إذا يبدأ تراكب لترسيخ قبل الطلاء، فإن النتائج ستكون uninterpretable. </li></ol></li><li style=";text-align:right;direction:rtl"> مزج الخليط تراكب بواسطة pipetting صعودا وهبوطا عدة مرات مع 5 مل الماصة والحرص على عدم إدخال فقاعات في الخليط. ماصة ببطء خليط تراكب مباشرة على لوحة TSA طعن. إبقاء لوحة على الفوق لبضع دقائق مما يسمح للأجار لتتصلب. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> لا تدوير لوحة لتوزيع الخليط تراكب، وهذا سيسحب من نمو ثقافة طعن في تراكب. </li></ol></li><li style=";text-align:right;direction:rtl"> وضع بعناية TSA وحة مع تراكب في الحاضنة 37 درجة مئوية تحتوي على 5٪ CO 2 O / N (حوالي 16-18 ساعة). </li><li style=";text-align:right;direction:rtl"> مراقبة لوحات بعد نمو بين عشية وضحاها. يجب أن تظهر لوحات مبهمة من النمو من سلالة تراكب إلا في المناطق التي حدث تثبيط أو فرمون إشارات. سوف تظهر هذه كمناطق إما واضحة أو الزرقاء حول سلالة طعن، على التوالي. ملاحظة: على الرغم من أن قياس آثافةيمكن تحديد تظهر عناصر من القطر من المقاصة زرقاء أو التقييم الكمي، والاختلافات في القطر ويمكن أيضا أن تختلف تبعا لكمية البكتيريا التي طعن في لوحة. الفحص تراكب هو فحص نوعي، ينبغي تفسير أي تقييم كمي بحذر. يعتبر أي المقاصة واضحة بالمقارنة مع سيطرة سلبية والنشاط. </li></ol>

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The authors have nothing to disclose.

هذا الاختبار تراكب هو وسيلة سريعة لتحديد نطاق النشاط للمنتجين مبيد جرثومي وإظهار التفاعلات التنافسية التي قد تحدث بين سلالات المكورات الرئوية. الفحص تراكب يمكن تكييفها لاستخدامها لفحص سلالات متعددة لإنتاج مبيد جرثومي على لوحة واحدة. قمنا بنجاح فحص مجموعات سلالة كب...

العقدية الرئوية، وهي المستعمر المشترك للمجتمع متعدد المكروبات من البلعوم الأنفي، غير قادرة على المنافسة مع الآخرين، والمكورات الرئوية وثيقي الصلة من خلال إنتاج الببتيدات المضادة للميكروبات أنتجت البكتريا (bacteriocins). كل سلالة المكورات الرئوية التسلسل بالكامل بحثت حتى الآن يحتوي على نسخة من ب acteriocin- ل آيك ص eptide موضع، BLP. وقد تجلى إنتاج مبيد جرثومي من المكورات الرئوية إلى أن تكون مهمة في نتائج سواء في المختبر وفي الجسم الحي المنافسة 1-4. وتتأثر ديناميكية تنافسية من خلال التعبير عن bacteriocins المتنوعة جنبا إلى جنب مع البروتينات الحصانة وما شابه ذلك ردا على الببتيد فرمون محددة. يتم التحكم تحريض موضع BLP عن طريق نظام الاستشعار عن النصاب فيه فرمون الببتيد، BlpC، بربط كيناز الاستشعار، BlpH، ويبدأ شلال يشير مما أدى إلىالنسخ من موضع 5،6 BLP. هناك أربعة اختلافات أليلية من BlpC أن كل مأزق لBlpH المشابهة لها 6. للخلية من أجل البقاء آثار مبيد جرثومي الخاص بها، ونسخه الجينات التي تشفر البروتينات الحصانة وما شابه ذلك على نفس الاوبرون حيث أن كل من الجينات مبيد جرثومي. يحدث إذا قتل سلالة منافس غير قادر على upregulate موضع BLP ردا على فرمون خارجي أو، إذا كان يفتقر إلى سلالة الجين الحصانة معين المطلوبة للحماية. مجمع نقل، مطلوب BlpAB عن إفراز وتجهيز فرمون الببتيد والببتيدات مبيد جرثومي 2،4. في الآونة الأخيرة، فقد تبين أن نسبة كبيرة من سلالات المكورات الرئوية هي &quot;الغشاشون&quot; يعني لديهم طفرة في الجين الحفظ blpA مما يجعلها غير قادرة على إفراز الفيرمونات وbacteriocins 1،2. هذه السلالات هي قادرة على الاستجابة لBlpC خارجية المنشأ 2 يفرزها صهيلسلالات مملة السماح لإنتاج البروتينات الحصانة. وعلى الرغم من الاستعدادات الخام من bacteriocins من supernatants يمكن إعداد من سلالات منتج باستخدام أساليب الخطوات البيوكيميائية لتحقيق النقاء، وهذا النهج ليس مفيدا لفحص مجموعات كبيرة من العزلات وإذا كان مستوى التعبير مبيد جرثومي منخفضة في مرق نمت الثقافات 2،7- 9. يستخدم الفحص تراكب كوسيلة سريعة للتحقيق في الديناميات التنافسية بين السلالات التي قد تكون موجودة في المختبر. للقيام بذلك، سلالة المكورات الرئوية هو على لوحة آغار وسمح لتنمو لتحقيق تركيزات البكتيرية محلية كافية لتحريض موضع BLP تلقيح مسبقا. ثم يتم تلقيح سلالة الثاني في حل أجار لينة المنصهر التي يتم بعد ذلك تطبيقها على سلالة تلقيح قبل لاختبار حساسية. لتقييم لنشاط موضع BLP (مستقلة عن النشاط المثبطة)، سلالات يمكن مضافين مع سلسلة من عشرالعناصر الأرضية النادرة التي سبق وصفها سلالات مراسل BlpC. شيدت هذه السلالات لاحتواء واحد من ثلاثة blpH الأليلات المختلفة التي تستجيب لالفيرومونات BlpC الثلاثة الأكثر شيوعا التي يفرزها المكورات الرئوية. سلالات مراسل لها الجين lacZ المتكاملة التي هي تحت سيطرة المروج يعتمد BlpH وتحمل الحذف في الجينات blpC يمنع التحفيز الذاتي 10،11.

<table border="0" cellpadding="0" cellspacing="0" width="753">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Name of Material/ Equipment</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:351px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Trypticase Soy Agar with 5% Sheep Blood</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">B21261X&#160;</td>
			<td>For growth from freezer cultures</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Catalase</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">C100-500mg</td>
			<td>4,741 Units per plate</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Todd Hewitt Broth + Yeast Extract (THY)</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">DF0492-17-6&#160;</td>
			<td>30 g of THB, 5 g yeast extract, 1 L ddH20 autoclave</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">Trypticase Soy Broth + Agar plates (TSA)</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">B11768&#160;</td>
			<td>30 g of TS, 15 g agar, 1 L ddH20 autoclave</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:212px;">5-Bromo-4-chloro-3-indolyl &#946;-D-galactopyranoside (X-gal)</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">B4252-50MG</td>
			<td>Dissolve in dimethylformamide</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Petri dishes</td>
			<td style="width:71px;">Fisher</td>
			<td>FB0875712</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">Spectrophometer</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>Measures the OD620 of cultures</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">37 &#176;C water bath</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">37 &#176;C incubator with 5% CO2</td>
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			<td height="21" style="height:21px;width:212px;">15 ml conical tube</td>
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using the overlay assay to qualitatively measure bacterial production of and sensitivity to pneumococcal bacteriocins

Streptococcus pneumoniae colonizes the highly diverse polymicrobial community of the nasopharynx where it must compete with resident organisms. We have shown that bacterially produced antimicrobial peptides (bacteriocins) dictate the outcome of these competitive interactions. All fully-sequenced pneumococcal strains harbor a bacteriocin-like peptide (blp) locus. The blp locus encodes for a range of diverse bacteriocins and all of the highly conserved components needed for their regulation, processing, and secretion. The diversity of the bacteriocins found in the bacteriocin immunity region (BIR) of the locus is a major contributor of pneumococcal competition. Along with the bacteriocins, immunity genes are found in the BIR and are needed to protect the producer cell from the effects of its own bacteriocin. The overlay assay is a quick method for examining a large number of strains for competitive interactions mediated by bacteriocins. The overlay assay also allows for the characterization of bacteriocin-specific immunity, and detection of secreted quorum sensing peptides. The assay is performed by pre-inoculating an agar plate with a strain to be tested for bacteriocin production followed by application of a soft agar overlay containing a strain to be tested for bacteriocin sensitivity. A zone of clearance surrounding the stab indicates that the overlay strain is sensitive to the bacteriocins produced by the pre-inoculated strain. If no zone of clearance is observed, either the overlay strain is immune to the bacteriocins being produced or the pre-inoculated strain does not produce bacteriocins. To determine if the blp locus is functional in a given strain, the overlay assay can be adapted to evaluate for peptide pheromone secretion by the pre-inoculated strain. In this case, a series of four lacZ-reporter strains with different pheromone specificity are used in the overlay.

هناك نوعان من النتائج المحتملة في مقايسة تراكب. يجب أن يكون من الممكن أن نرى النمو من سلالة طعن بعد الحضانة بين عشية وضحاها. في الشكل 1A، سلالة تراكب حساس لbacteriocins التي يتم إنتاجها. منطقة التخليص يمكن تصور المحيطة سلالة طعن. بالإضافة إلى ذلك، دوامات من سلالة طع?...

Watch this Scientific Journal Video about Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins at JoVE.com

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Competition in Streptococcus pneumoniae is mediated by bacteriocins, small antimicrobial peptides with inhibitory activity towards pneumococcus and other related species.&#160; Here we describe an optimized bacterial overlay assay that allows for the characterization of bacteriocin activity and inhibitory spectrum, bacteriocin-specific immunity, and detection of secreted quorum sensing peptides.

باستخدام تراكب الفحص لقياس نوعيا الإنتاج الجرثومي من والحساسية للالرئوية Bacteriocins

Streptococcus pneumoniae colonizes the highly diverse polymicrobial community of the nasopharynx where it must compete with resident organisms.  We have ...

using-overlay-assay-to-qualitatively-measure-bacterial-production

Research

JoVE Journal

Immunology and Infection

13.4K Views.  University of Michigan. Competition in Streptococcus pneumoniae is mediated by bacteriocins, small antimicrobial peptides with inhibitory activity towards pneumococcus and other related species.  Here we describe an optimized bacterial overlay assay that allows for the characterization of bacteriocin activity and inhibitory spectrum, bacteriocin-specific immunity, and detection of secreted quorum sensing peptides. 

Video: Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Using Luciferase to Image Bacterial Infections in Mice

Imaging is a valuable technique that can be used to monitor biological processes. In particular, the presence of cancer cells, stem cells, specific immune cell types, viral pathogens, parasites and bacteria can be followed in real-time within living animals 1-2. Application of bioluminescence imaging to the study of pathogens has advantages as compared to conventional strategies for analysis of infections in animal models3-4. Infections can be visualized within individual animals over time, without requiring euthanasia to determine the location and quantity of the pathogen. Optical imaging allows comprehensive examination of all tissues and organs, rather than sampling of sites previously known to be infected. In addition, the accuracy of inoculation into specific tissues can be directly determined prior to carrying forward animals that were unsuccessfully inoculated throughout the entire experiment. Variability between animals can be controlled for, since imaging allows each animal to be followed individually. Imaging has the potential to greatly reduce animal numbers needed because of the ability to obtain data from numerous time points without having to sample tissues to determine pathogen load3-4.
This protocol describes methods to visualize infections in live animals using bioluminescence imaging for recombinant strains of bacteria expressing luciferase. The click beetle (CBRLuc) and firefly luciferases (FFluc) utilize luciferin as a substrate5-6. The light produced by both CBRluc and FFluc has a broad wavelength from 500 nm to 700 nm, making these luciferases excellent reporters for the optical imaging in living animal models7-9. This is primarily because wavelengths of light greater than 600 nm are required to avoid absorption by hemoglobin and, thus, travel through mammalian tissue efficiently. Luciferase is genetically introduced into the bacteria to produce light signal10. Mice are pulmonary inoculated with bioluminescent bacteria intratracheally to allow monitoring of infections in real time. After luciferin injection, images are acquired using the IVIS Imaging System. During imaging, mice are anesthetized with isoflurane using an XGI-8 Gas Anethesia System. Images can be analyzed to localize and quantify the signal source, which represents the bacterial infection site(s) and number, respectively. After imaging, CFU determination is carried out on homogenized tissue to confirm the presence of bacteria. Several doses of bacteria are used to correlate bacterial numbers with luminescence. Imaging can be applied to study of pathogenesis and evaluation of the efficacy of antibacterial compounds and vaccines.

Methods for bioluminescence imaging of bacterial infections in living animals are decribed. Pathogens are modified to express luciferase allowing optical whole body imaging of infections in live animals. Animal models can be infected with luciferase expressing pathogens and the resulting course of disease visualized in real-time by bioluminescence imaging.

Luciferase به لالتهابات جرثومية في صورة الفئران

Imaging is a valuable technique that can be used to monitor biological processes.  In particular, the presence of cancer cells, stem cells, specific ...

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb (BCG lux/M.Tb lux)

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal titers. Studies of serum bactericidal titers in response to childhood vaccines have enabled us to develop and validate cut-off levels for protective immune responses and such cut-offs are in routine use. No such assays have been taken forward into the routine assessment of vaccines that induce primarily cell-mediated immunity in the form of effector T cell responses, such as TB vaccines. In the animal model, the performance of a given vaccine candidate is routinely evaluated in standardized bactericidal assays, and all current novel TB-vaccine candidates have been subjected to this step in their evaluation prior to phase 1 human trials. The assessment of immunogenicity and therefore likelihood of protective efficacy of novel anti-TB vaccines should ideally undergo a similar step-wise evaluation in the human models now, including measurements in bactericidal assays.
Bactericidal assays in the context of tuberculosis vaccine research are already well established in the animal models, where they are applied to screen potentially promising vaccine candidates. Reduction of bacterial load in various organs functions as the main read-out of immunogenicity. However, no such assays have been incorporated into clinical trials for novel anti-TB vaccines to date.
Although there is still uncertainty about the exact mechanisms that lead to killing of mycobacteria inside human macrophages, the interaction of macrophages and T cells with mycobacteria is clearly required. The assay described in this paper represents a novel generation of bactericidal assays that enables studies of such key cellular components with all other cellular and humoral factors present in whole blood without making assumptions about their relative individual contribution. The assay described by our group uses small volumes of whole blood and has already been employed in studies of adults and children in TB-endemic settings. We have shown immunogenicity of the BCG vaccine, increased growth of mycobacteria in HIV-positive patients, as well as the effect of anti-retroviral therapy and Vitamin D on mycobacterial survival in vitro. Here we summarise the methodology, and present our reproducibility data using this relatively simple, low-cost and field-friendly model.
Note: Definitions/Abbreviations
BCG lux = M. bovis BCG, Montreal strain, transformed with shuttle plasmid pSMT1 carrying the luxAB genes from Vibrio harveyi, under the control of the mycobacterial GroEL (hsp60) promoter. 
CFU = Colony Forming Unit (a measure of mycobacterial viability).

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb BCG lux/M.Tb lux

We describe an alternative approach to the enumeration of mycobacteria in vitro, which uses reporter-gene tagged mycobacteria instead of colony-forming units (CFU). &#x201C;Survival&#x201D; of organisms as well as host response-markers are measured simultaneously, providing a low-cost, versatile and functional system for studies of host/pathogen interactions in the context of tuberculosis.

وظيفية فحص الدم لقياس الجامعة صلاحية مايكوباكتيريا ، وذلك باستخدام الجينات المرتبطة دلاليا مراسل بي سي جي إم أو السل (BCG لوكس / M. التربيوم لوكس)

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal ...

A Visual Assay to Monitor T6SS-mediated Bacterial Competition

Type VI secretion systems (T6SSs) are molecular nanomachines allowing Gram-negative bacteria to transport and inject proteins into a wide variety of target cells1,2. The T6SS is composed of 13 core components and displays structural similarities with the tail-tube of bacteriophages3. The phage uses a tube and a puncturing device to penetrate the cell envelope of target bacteria and inject DNA. It is proposed that the T6SS is an inverted bacteriophage device creating a specific path in the bacterial cell envelope to drive effectors and toxins to the surface. The process could be taken further and the T6SS device could perforate other cells with which the bacterium is in contact, thus injecting the effectors into these targets. The tail tube and puncturing device parts of the T6SS are made with Hcp and VgrG proteins, respectively4,5.
The versatility of the T6SS has been demonstrated through studies using various bacterial pathogens. The Vibrio cholerae T6SS can remodel the cytoskeleton of eukaryotic host cells by injecting an "evolved" VgrG carrying a C-terminal actin cross-linking domain6,7. Another striking example was recently documented using Pseudomonas aeruginosa which is able to target and kill bacteria in a T6SS-dependent manner, therefore promoting the establishment of bacteria in specific microbial niches and competitive environment8,9,10.
In the latter case, three T6SS-secreted proteins, namely Tse1, Tse2 and Tse3 have been identified as the toxins injected in the target bacteria (Figure 1). The donor cell is protected from the deleterious effect of these effectors via an anti-toxin mechanism, mediated by the Tsi1, Tsi2 and Tsi3 immunity proteins8,9,10. This antimicrobial activity can be monitored when T6SS-proficient bacteria are co-cultivated on solid surfaces in competition with other bacterial species or with T6SS-inactive bacteria of the same species8,11,12,13.
The data available emphasized a numerical approach to the bacterial competition assay, including time-consuming CFU counting that depends greatly on antibiotic makers. In the case of antibiotic resistant strains like P. aeruginosa, these methods can be inappropriate. Moreover, with the identification of about 200 different T6SS loci in more than 100 bacterial genomes14, a convenient screening tool is highly desirable. We developed an assay that is easy to use and requires standard laboratory material and reagents. The method offers a rapid and qualitative technique to monitor the T6SS-dependent bactericidal/bacteriostasis activity by using a reporter strain as a prey (in this case Escherichia coli DH5&alpha;) allowing a-complementation of the lacZ gene. Overall, this method is graphic and allows rapid identification of T6SS-related phenotypes on agar plates. This experimental protocol may be adapted to other strains or bacterial species taking into account specific conditions such as growth media, temperature or time of contact.

We describe a qualitative assay to monitor bacterial competition mediated by the Pseudomonas aeruginosa type VI secretion system (T6SS). The assay relies on the survival/killing of Escherichia coli target cells carrying a lacZ-reporter. This technique is adjustable to assess the bactericidal/bacteriostasis activity of T6SS-proficient microorganisms.

A الفحص المرئي لمراقبة T6SS بوساطة المسابقة الجرثومي

Type VI secretion systems (T6SSs) are molecular  nanomachines allowing Gram-negative bacteria to transport and inject proteins  into a wide variety of ...

Using Click Chemistry to Measure the Effect of Viral Infection on Host-Cell RNA Synthesis

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, it is therefore important to have a quick and reliable way of measuring transcriptional activity in infected cells. Traditionally, transcription has been measured either by incorporation of radioactive nucleosides such as 3H-uridine followed by detection via autoradiography or scintillation counting, or incorporation of halogenated uridine analogs such as 5-bromouridine (BrU) followed by detection via immunostaining. The use of radioactive isotopes, however, requires specialized equipment and is not feasible in a number of laboratory settings, while the detection of BrU can be cumbersome and may suffer from low sensitivity.
The recently developed click chemistry, which involves a copper-catalyzed triazole formation from an azide and an alkyne, now provides a rapid and highly sensitive alternative to these two methods. Click chemistry is a two step process in which nascent RNA is first labeled by incorporation of the uridine analog 5-ethynyluridine (EU), followed by detection of the label with a fluorescent azide. These azides are available as several different fluorophores, allowing for a wide range of options for visualization.
This protocol describes a method to measure transcriptional suppression in cells infected with the Rift Valley fever virus (RVFV) strain MP-12 using click chemistry. Concurrently, expression of viral proteins in these cells is determined by classical intracellular immunostaining. Steps 1 through 4 detail a method to visualize transcriptional suppression via fluorescence microscopy, while steps 5 through 8 detail a method to quantify transcriptional suppression via flow cytometry. This protocol is easily adaptable for use with other viruses.

This method describes the use of click chemistry to measure changes in host cell transcription after infection with the Rift Valley fever virus (RVFV) strain MP-12. Results can be visualized qualitatively via fluorescence microscopy or obtained quantitatively through flow cytometry. This method is adaptable for use with other viruses.

باستخدام الكيمياء فوق لقياس تأثير عدوى فيروسية في خلية المضيف RNA التجميعي

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, ...

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a prerequisite for pneumococcal infections such as pneumonia and otitis media. In vitro adherence assays can be used to study the attachment of pneumococci to epithelial cell monolayers and to investigate potential interventions, such as the use of probiotics, to inhibit pneumococcal&#160;colonization.&#160;The protocol described here is used to investigate the effects of the probiotic Streptococcus salivarius on the adherence of pneumococci to the human epithelial cell line CCL-23 (sometimes referred to as HEp-2 cells). The assay involves three main steps: 1) preparation of epithelial and bacterial cells, 2) addition of bacteria to epithelial cell monolayers, and 3) detection of adherent pneumococci by viable counts (serial dilution and plating) or quantitative real-time PCR (qPCR). This technique is relatively straightforward and does not require specialized equipment other than a tissue culture setup. The assay can be used to test other probiotic species and/or potential inhibitors of pneumococcal colonization and can be easily modified to address other scientific questions regarding pneumococcal adherence and invasion.

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

In vitro adherence assays can be used to study the attachment of Streptococcus pneumoniae to epithelial cell monolayers and to investigate potential interventions such as the use of probiotics for inhibiting pneumococcal colonization.

التحقيق في آثار البروبيوتيك على المكورات الرئوية الاستعمار باستخدام<em&gt; في المختبر</em&gt; الالتزام الفحص

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a ...

Cell-based Flow Cytometry Assay to Measure Cytotoxic Activity

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells to kill CD4+ T cells loaded with their cognate peptide. Target CD4+ T cells are divided into two populations, labeled with two different concentrations of CFSE. One population is pulsed with the peptide of interest (CFSE-low) while the other remains un-pulsed (CFSE-high). Pulsed and un-pulsed CD4+ T cells are mixed at an equal ratio and incubated with an increasing number of purified CD8+ T cells. The specific killing of autologous target CD4+ T cells is analyzed by flow cytometry after coculture with CD8+ T cells containing the antigen-specific effector CD8+ T cells detected by peptide/MHCI tetramer staining. The specific lysis of target CD4+ T cells measured at different effector versus target ratios, allows for the calculation of lytic units, LU30/106 cells. This simple and straightforward assay allows for the accurate measurement of the intrinsic capacity of CD8+ T cells to kill target CD4+ T cells.

This protocol describes a sensitive, cell-based cytotoxicity assay. By enumerating the decrease in frequency of live target CD4+ T cells in the presence of an increasing number of effector CD8+ T cells, this assay allows for the direct assessment of cytolytic activity of antigen-specific CD8+ T cells.

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells ...

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal epidemiology, capsular serotyping can provide useful information for vaccine efficacy and impact studies.&#160;The Quellung reaction is the gold standard method for pneumococcal capsular serotyping. The method involves testing a pneumococcal cell suspension with pooled and specific antisera directed against the capsular polysaccharide. The antigen-antibody reactions are observed microscopically. The protocol has three main steps: 1) preparation of a bacterial cell suspension, 2) mixing of cells and antisera on a glass slide, and 3) reading the Quellung reaction using a microscope. The Quellung reaction is reasonably simple to perform and can be applied wherever a suitable microscope and antisera are available.

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

The Quellung reaction is the gold standard technique for serotyping Streptococcus pneumoniae. This technique utilizes a microscope and specific pneumococcal antisera and is commonly used in reference and research laboratories worldwide.

المحفظة المصلي من<em&gt; العقدية الرئوية</em&gt; باستخدام تفاعل الانتباج

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal ...

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major cause of morbidity and mortality world-wide. Current vaccines target the pneumococcal capsule, and there are over 90 capsular serotypes. Serotyping pneumococcal isolates is therefore important for assessing the impact of vaccination programs and for epidemiological purposes. The World Health Organization has recommended latex agglutination as an alternative method to the &#8216;gold standard&#8217; Quellung test for serotyping pneumococci. Latex agglutination is a relatively simple, quick and inexpensive method; and is therefore suitable for resource-poor settings as well as laboratories with high-volume workloads. Latex agglutination reagents can be prepared in-house utilizing commercially-sourced antibodies that are passively attached to latex particles. This manuscript describes a method of production and quality control of latex agglutination reagents, and details a sequential testing approach which is time- and cost-effective. 
This method of production and quality control may also be suitable for other testing purposes.

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination testing is a simple, rapid and inexpensive method for serotyping Streptococcus pneumoniae, and has also been widely applied in diagnostic microbiology. This manuscript describes the in-house production of latex agglutination reagents, quality control procedures and the application of this technique to pneumococcal serotyping.

المحفظة المصلي من<em&gt; العقدية الرئوية</em&gt; من جانب تراص اللاتكس

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major ...

Methods to Inhibit Bacterial Pyomelanin Production and Determine the Corresponding Increase in Sensitivity to Oxidative Stress

Pyomelanin is an extracellular red-brown pigment produced by several bacterial and fungal species. This pigment is derived from the tyrosine catabolism pathway and contributes to increased oxidative stress resistance. Pyomelanin production in Pseudomonas aeruginosa is reduced in a dose dependent manner through treatment with 2-[2-nitro-4-(trifluoromethyl)benzoyl]-1,3-cyclohexanedione (NTBC). We describe a titration method using multiple concentrations of NTBC to determine the concentration of drug that will reduce or abolish pyomelanin production in bacteria. The titration method has an easily quantifiable outcome, a visible reduction in pigment production with increasing drug concentrations. We also describe a microtiter plate method to assay antibiotic minimum inhibitory concentration (MIC) in bacteria. This method uses a minimum of resources and can easily be scaled up to test multiple antibiotics in one microtiter plate for one strain of bacteria. The MIC assay can be adapted to test the affects of non-antibiotic compounds on bacterial growth at specific concentrations. Finally, we describe a method for testing bacterial sensitivity to oxidative stress by incorporating H2O2 into agar plates and spotting multiple dilutions of bacteria onto the plates. Sensitivity to oxidative stress is indicated by reductions in colony number and size for the different dilutions on plates containing H2O2 compared to a no H2O2 control. The oxidative stress spot plate assay uses a minimum of resources and low concentrations of H2O2. Importantly, it also has good reproducibility. This spot plate assay could be adapted to test bacterial sensitivity to various compounds by incorporating the compounds in agar plates and characterizing the resulting bacterial growth.

Bacterial pyomelanin production results in increased resistance to oxidative stress and virulence. We report on techniques that can be used to determine inhibition of pyomelanin production and assay the resulting increase in sensitivity to oxidative stress in bacteria, as well as determine antibiotic minimum inhibitory concentration (MIC).

طرق لمنع البكتيرية Pyomelanin الإنتاج وتحديد الزيادة المقابلة في الحساسية للإجهاد التأكسدي

Pyomelanin is an extracellular red-brown pigment produced by several bacterial and fungal species. This pigment is derived from the tyrosine catabolism ...

Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds

The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, including work with bacteriophages and bacteriocins, proteinaceous antibacterial agents. This approach is relatively inexpensive, with minimal resource requirements. This technique consists of spotting supernatant from a donor strain (potentially harboring a toxic compound(s)) onto a solidified soft agar overlay that is seeded with a bacterial test strain (potentially sensitive to the toxic compound(s)). We utilized this technique to screen a library of Pseudomonas syringae strains for intraspecific killing. By combining this approach with a precipitation step and targeted gene deletions, multiple toxic compounds produced by the same strain can be differentiated. The two antagonistic agents commonly recovered using this technique are bacteriophages and bacteriocins. These two agents can be differentiated using two simple additional tests. Performing a serial dilution on a supernatant containing bacteriophage will result in individual plaques becoming less in number with greater dilution, whereas serial dilution of a supernatant containing bacteriocin will result a clearing zone that becomes uniformly more turbid with greater dilution. Additionally, a bacteriophage will produce a clearing zone when spotted onto a fresh soft agar overlay seeded with the same strain, whereas a bacteriocin will not produce a clearing zone when transferred to a fresh soft agar lawn, owing to the dilution of the bacteriocin.

We describe a simple method for screening bacterial cultures for the production of compounds inhibitory towards other bacteria.