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The formation of persister cells is one mechanism by which bacteria can survive exposure to environmental stresses. We show that Campylobacter jejuni 11168H forms persister cells at a frequency of 10−3 after exposure to 100 × MIC of penicillin G for 24 h. Staining the cell population with a redox sensitive fluorescent dye revealed that penicillin G treatment resulted in the appearance of a population of cells with increased fluorescence. We present evidence, to show this could be a consequence of increased redox protein activity in, or associated with, the electron transport chain. These data suggest that a population of penicillin G treated C. jejuni cells could undergo a remodeling of the electron transport chain in order to moderate membrane hyperpolarization and intracellular alkalization; thus reducing the antibiotic efficacy and potentially assisting in persister cell formation.

Vibrio parahaemolyticus is the lead causative agent for seafood-borne human gastroenteritis. While its occurrence has traditionally been uncommon in Europe and the United Kingdom, rising sea surface temperatures have resulted in an increased prevalence. Here, we present the complete genome sequences of four novel V. parahaemolyticus strains isolated in the United Kingdom.

Viable but non-culturable (VBNC) cells are cells that are metabolically active, but are unable to form colonies on standard culture media. Following environmental stimuli, such as temperature upshift, some VBNC cells can ‘resuscitate’ restoring their ability to grow on media. Currently, over 80 bacterial species are reported to enter the VBNC state. The ability of VBNC cells to go undetected by conventional microbiological practices could lead to an underestimation of total viable cells in environmental and clinical samples. Furthermore, their capacity to retain virulence potential and their ability for renewed metabolic activity means the VBNC state in pathogens may pose a risk to human health and thus warrants further investigation. This research project has investigated the ability of the human pathogen Vibrio parahaemolyticus to form VBNC cells when exposed to stressful conditions. V. parahaemolyticus is a bacterium that is present in the marine environment and can be found in seawater, shellfish (such as oysters and mussels) and in crustacea (such as crab). This bacterium is the leading cause of seafood associated gastroenteritis worldwide and often results in watery/bloody diarrhea and vomiting. We have developed robust models to generate V. parahaemolyticus VBNC cells in the laboratory and report that different sub populations of VBNC cells can occur based upon their metabolic activity, cell shape and the ability to grow and cause disease in Galleria mellonella. Using mass spectrophotometry we have identified several proteins which may play roles in VBNC formation and resuscitation in V. parahaemolyticus.

A putative biosynthetic mechanism for selenium nanoparticles (SeNPs) and efficient reduction of selenite (SeO32-) in the bacterial strain Stenotrophomonas maltophilia SeITE02 are addressed here on the basis of information gained by a combined approach relying on a set of physiological, chemical/biochemical, microscopy, and proteomic analyses. S. maltophilia SeITE02 is demonstrated to efficiently transform selenite into elemental selenium (Se°) by reducing 100% of 0.5mM of this toxic oxyanion to Se° nanoparticles within 48h growth, in liquid medium. Since the selenite reducing activity was detected in the cytoplasmic protein fraction, while biogenic SeNPs showed mainly extracellular localization, a releasing mechanism of SeNPs from the intracellular environment is hypothesized. SeNPs appeared spherical in shape and with size ranging from 160nm to 250nm, depending on the age of the cultures. Proteomic analysis carried out on the cytoplasmic fraction identified an alcohol dehydrogenase homolog, conceivably correlated with the biogenesis of SeNPs. Finally, by Fourier Transformed Infrared Spectrometry, protein and lipid residues were detected on the surface of biogenic SeNPs. Eventually, this strain might be efficaciously exploited for the remediation of selenite-contaminated environmental matrices due to its high SeO32- reducing efficiency. Biogenic SeNPs may also be considered for technological applications in different fields.