Real-Time Monitoring of Single Bacterium Lysis and Leakage Events by Chemiluminescence Microscopy

The small size of bacteria makes it difficult to study the biochemistry inside single cells. The amount of material inside is limited; therefore, an ultrasensitive method is required to interrogate single cells. Using a sensitive ICCD detector to record chemiluminescence (CL) from an optimized firefly luciferase−ATP bioluminescence reaction system, we report for the first time real-time imaging of lysis and leakage of single bacterium with 10-s temporal resolution. Movies are generated to visualize how the cell membrane was damaged by phage lysis, antibiotics attack, or dehydration, as well as the wall repair and cell recovery processes. The results show single-cell variations that are not obtainable from bulk measurements, confirming that CL microscopy of luciferase-expressing bacteria is a powerful tool for studying the fundamental biology of cells

Real-Time Monitoring of Single Bacterium Lysis and Leakage Events by Chemiluminescence Microscopy

The small size of bacteria makes it difficult to study the biochemistry inside single cells. The amount of material inside is limited; therefore, an ultrasensitive method is required to interrogate single cells. Using a sensitive ICCD detector to record chemiluminescence (CL) from an optimized firefly luciferase−ATP bioluminescence reaction system, we report for the first time real-time imaging of lysis and leakage of single bacterium with 10-s temporal resolution. Movies are generated to visualize how the cell membrane was damaged by phage lysis, antibiotics attack, or dehydration, as well as the wall repair and cell recovery processes. The results show single-cell variations that are not obtainable from bulk measurements, confirming that CL microscopy of luciferase-expressing bacteria is a powerful tool for studying the fundamental biology of cells

Adhesive Tape Microfluidics with an Autofocusing Module That Incorporates CRISPR Interference: Applications to Long-Term Bacterial Antibiotic Studies

The ability to study bacteria at the single cell level has advanced our insights into microbial physiology and genetics in ways not attainable by studying large populations using more traditional culturing methods. To improve methods to characterize bacteria at the cellular level, we developed a new microfluidic platform that enables cells to be exposed to metabolites in a gradient of concentrations. By designing low-cost, three-dimensional devices with adhesive tapes and tailoring them for bacterial imaging, we avoided the complexities of silicon and polymeric microfabrication. The incorporation of an agarose membrane as the resting substrate, along with a temperature-controlled environmental chamber, allows the culturing of bacterial cells for over 10 h under stable growth or inhibition conditions. Incorporation of an autofocusing module helped the uninterrupted, high-resolution observation of bacteria at the single-cell and at low density population levels. We used the microfluidic platform to record morphological changes in Escherichia coli during ampicillin exposure and to quantify the minimum inhibitory concentration of the antibiotic. We further demonstrated the potential of finely-tuned, incremental gene regulation in a concentration gradient utilizing CRISPR interference (CRISPRi). These low-cost engineering tools, when implemented in combination with genetic approaches such as CRISPRi, should prove useful to uncover new genetic determinants of antibiotic susceptibility and evaluate the long-term effectiveness of antibiotics in bacterial cultures

Adhesive Tape Microfluidics with an Autofocusing Module That Incorporates CRISPR Interference: Applications to Long-Term Bacterial Antibiotic Studies

The ability to study bacteria at the single cell level has advanced our insights into microbial physiology and genetics in ways not attainable by studying large populations using more traditional culturing methods. To improve methods to characterize bacteria at the cellular level, we developed a new microfluidic platform that enables cells to be exposed to metabolites in a gradient of concentrations. By designing low-cost, three-dimensional devices with adhesive tapes and tailoring them for bacterial imaging, we avoided the complexities of silicon and polymeric microfabrication. The incorporation of an agarose membrane as the resting substrate, along with a temperature-controlled environmental chamber, allows the culturing of bacterial cells for over 10 h under stable growth or inhibition conditions. Incorporation of an autofocusing module helped the uninterrupted, high-resolution observation of bacteria at the single-cell and at low density population levels. We used the microfluidic platform to record morphological changes in Escherichia coli during ampicillin exposure and to quantify the minimum inhibitory concentration of the antibiotic. We further demonstrated the potential of finely-tuned, incremental gene regulation in a concentration gradient utilizing CRISPR interference (CRISPRi). These low-cost engineering tools, when implemented in combination with genetic approaches such as CRISPRi, should prove useful to uncover new genetic determinants of antibiotic susceptibility and evaluate the long-term effectiveness of antibiotics in bacterial cultures

Data_Sheet_1_Methionyl-tRNA synthetase synthetic and proofreading activities are determinants of antibiotic persistence.PDF

Bacterial antibiotic persistence is a phenomenon where bacteria are exposed to an antibiotic and the majority of the population dies while a small subset enters a low metabolic, persistent, state and are able to survive. Once the antibiotic is removed the persistent population can resuscitate and continue growing. Several different molecular mechanisms and pathways have been implicated in this phenomenon. A common mechanism that may underly bacterial antibiotic persistence is perturbations in protein synthesis. To investigate this mechanism, we characterized four distinct metG mutants for their ability to increase antibiotic persistence. Two metG mutants encode changes near the catalytic site of MetRS and the other two mutants changes near the anticodon binding domain. Mutations in metG are of particular interest because MetRS is responsible for aminoacylation both initiator tRNAMet and elongator tRNAMet indicating that these mutants could impact translation initiation and/or translation elongation. We observed that all the metG mutants increased the level of antibiotic persistence as did reduced transcription levels of wild type metG. Although, the MetRS variants did not have an impact on MetRS activity itself, they did reduce translation rates. It was also observed that the MetRS variants affected the proofreading mechanism for homocysteine and that these mutants’ growth is hypersensitive to homocysteine. Taken together with previous findings, our data indicate that both reductions in cellular Met-tRNAMet synthetic capacity and reduced proofreading of homocysteine by MetRS variants are positive determinants for bacterial antibiotic persistence.</p

Adhesive Tape Microfluidics with an Autofocusing Module That Incorporates CRISPR Interference: Applications to Long-Term Bacterial Antibiotic Studies

The ability to study bacteria at the single cell level has advanced our insights into microbial physiology and genetics in ways not attainable by studying large populations using more traditional culturing methods. To improve methods to characterize bacteria at the cellular level, we developed a new microfluidic platform that enables cells to be exposed to metabolites in a gradient of concentrations. By designing low-cost, three-dimensional devices with adhesive tapes and tailoring them for bacterial imaging, we avoided the complexities of silicon and polymeric microfabrication. The incorporation of an agarose membrane as the resting substrate, along with a temperature-controlled environmental chamber, allows the culturing of bacterial cells for over 10 h under stable growth or inhibition conditions. Incorporation of an autofocusing module helped the uninterrupted, high-resolution observation of bacteria at the single-cell and at low density population levels. We used the microfluidic platform to record morphological changes in Escherichia coli during ampicillin exposure and to quantify the minimum inhibitory concentration of the antibiotic. We further demonstrated the potential of finely-tuned, incremental gene regulation in a concentration gradient utilizing CRISPR interference (CRISPRi). These low-cost engineering tools, when implemented in combination with genetic approaches such as CRISPRi, should prove useful to uncover new genetic determinants of antibiotic susceptibility and evaluate the long-term effectiveness of antibiotics in bacterial cultures

Adhesive Tape Microfluidics with an Autofocusing Module That Incorporates CRISPR Interference: Applications to Long-Term Bacterial Antibiotic Studies

The ability to study bacteria at the single cell level has advanced our insights into microbial physiology and genetics in ways not attainable by studying large populations using more traditional culturing methods. To improve methods to characterize bacteria at the cellular level, we developed a new microfluidic platform that enables cells to be exposed to metabolites in a gradient of concentrations. By designing low-cost, three-dimensional devices with adhesive tapes and tailoring them for bacterial imaging, we avoided the complexities of silicon and polymeric microfabrication. The incorporation of an agarose membrane as the resting substrate, along with a temperature-controlled environmental chamber, allows the culturing of bacterial cells for over 10 h under stable growth or inhibition conditions. Incorporation of an autofocusing module helped the uninterrupted, high-resolution observation of bacteria at the single-cell and at low density population levels. We used the microfluidic platform to record morphological changes in Escherichia coli during ampicillin exposure and to quantify the minimum inhibitory concentration of the antibiotic. We further demonstrated the potential of finely-tuned, incremental gene regulation in a concentration gradient utilizing CRISPR interference (CRISPRi). These low-cost engineering tools, when implemented in combination with genetic approaches such as CRISPRi, should prove useful to uncover new genetic determinants of antibiotic susceptibility and evaluate the long-term effectiveness of antibiotics in bacterial cultures

Average mice weight gain for the three diets over the duration of behavioral testing.

<p>The weights of the mice were determined every other day for the duration of testing. Values represent the mean weight in each group ± SEM, n = 16/group.</p

Behavioral and locomotion tests.

<p>10A. The number of entries to the open arm for the three groups. There were no significant differences detected between NCS and OS-HA7 or HA7 and OS-HA7, but there were significant differences between NCS and HA7. Values represent the mean number of entries to open arm in each group ± SEM, n = 16/group. *<i>p</i><0.05. 10B. Time spent in the open arm for the three groups. There were no significant differences detected between NCS and OS-HA7, but there were significant differences between NCS and HA7 and OS-HA7 and HA7. Values represent the mean time spent in the open arm in each group ± SEM, n = 16/group. *<i>p</i><0.05. 10C. Time spent in the closed arm for the three groups. There were no significant differences detected between NCS and OS-HA7, but there were significant differences between NCS and HA7 and OS-HA7 and HA7. Values represent the mean time spent in the closed arm in each group ± SEM, n = 16/group. *<i>p</i><0.05. 10D. Overall locomotion of mice during the open field test (10D). Values represent the mean time spent in each quadrant in each group ± SEM, n = 16/group. *<i>p</i><0.05. 10E. Overall locomotion of mice during the open field test (10E). Values represent the mean distance travelled ± SEM, n = 16/group.</p

Bacterial Community Profiling of Milk Samples as a Means to Understand Culture-Negative Bovine Clinical Mastitis

<div><p></p><p>Inflammation and infection of bovine mammary glands, commonly known as mastitis, imposes significant losses each year in the dairy industry worldwide. While several different bacterial species have been identified as causative agents of mastitis, many clinical mastitis cases remain culture negative, even after enrichment for bacterial growth. To understand the basis for this increasingly common phenomenon, the composition of bacterial communities from milk samples was analyzed using culture independent pyrosequencing of amplicons of 16S ribosomal RNA genes (16S rDNA). Comparisons were made of the microbial community composition of culture negative milk samples from mastitic quarters with that of non-mastitic quarters from the same animals. Genomic DNA from culture-negative clinical and healthy quarter sample pairs was isolated, and amplicon libraries were prepared using indexed primers specific to the V1–V2 region of bacterial 16S rRNA genes and sequenced using the Roche 454 GS FLX with titanium chemistry. Evaluation of the taxonomic composition of these samples revealed significant differences in the microbiota in milk from mastitic and healthy quarters. Statistical analysis identified seven bacterial genera that may be mainly responsible for the observed microbial community differences between mastitic and healthy quarters. Collectively, these results provide evidence that cases of culture negative mastitis can be associated with bacterial species that may be present below culture detection thresholds used here. The application of culture-independent bacterial community profiling represents a powerful approach to understand long-standing questions in animal health and disease.</p> </div