Characterization of E. coli E38???s Persistence to Bacterial Predation

Abstract

Department of Biological SciencesThe threat of multidrug-resistant bacteria is a major problem the world is facing currently. As many of the antibiotics available continue to fail at combating the ???superbugs???, the necessity of finding new methods or ways to combat them becomes a priority. As an alternative or supplement to chemical antibiotics, predatory bacteria, such as Bdellovibrio bacteriovorus, are thought to be promising candidates since they can prey on a wide range of the other gram-negative bacteria, including more than 100 human pathogens and antibiotic-resistant strains. However, some recent researchers have found that some bacterial strains appear to be resistant to predation by B. bacteriovorus, with no knowledge on the how or why. One such strain is the pathogen Escherichia coli E38. We found out that E. coli E38 appeared to be resistant to predation by cell viability test, however with cell viability assay and confocal microscopy, we also found that there was some level of predation occurred. This result is similar to that of antibiotic persisters in that the sub-population remains viable even in the presence of B. bacteriovorus. Bacteria persisters is a sub-population of bacteria that can survive from antibiotics without a genetic basis of resistance but due to metabolic/phenotypic variations within the entire population. These survivors are clinically important since they are relevant to chronic infection and relapse. Through further studies, we found that E. coli MG1655 antibiotic persisters (AP), which were induced by pre-treatment with antibiotics, were resistant to predation by B. bacteriovorus. Conversely, the sub-population of prey which survived predation, i.e., predation persisters (PP), were more resistant to antibiotics. Moreover, a starved population of E. coli E38 showed similar survival when exposed to antibiotics to predation persister while those of E. coli MG1655 did not. This demonstrates that the persistence tendency of the two E. coli is not identical. Consequently, our work shows persistence is a mechanism that bacteria could utilize to prevent their predation, and this persistence could be a potential answer for explaining E. coli E38???s resistance against bacterial predation. The difference in persistence tendencies between both E. coli strains suggests that the stress factor triggering this phenomenon and which evokes persistence in E. coli E38 is not clear and may be due to the numerous TA systems present within this bacterium, an idea that should be studied further.clos