Human bacterial pathogens face formidable challenges upon host cell interactions including reactive oxygen species, osmotic (salt), heat, acid, and bile salt stresses. Environmental cues trigger bacterial responses leading to either increased susceptibility or increased resistance to these stresses. One poorly studied environmental cue is low-shear microgravity, which is encountered by astronauts in outer space and may alter the response of microflora bacteria to stressful conditions. The human gastric pathogen Helicobacter pylori has not previously been examined for responses to stresses under microgravity conditions yet has abundant stress resistance mechanisms. We cultured H. pylori in chemically-defined medium under normal or microgravity conditions in high-aspect ratio vessels (HARVs) and subjected the bacteria to some of these stresses. Bacterial viability was similar between cultures prior to stress treatments as determined by ATP assays and viable count data. No difference in killing was observed between the two gravity conditions under high salt stress. For the bile salt deoxycholate, we observed a dose-dependent killing of H. pylori cultured under normal gravity conditions; this killing was significantly reduced when H. pylori was cultured under microgravity conditions. For hydrogen peroxide, a reactive oxygen species, we observed that H. pylori cultured under microgravity conditions survived far better than when cultured under normal gravity conditions in a dose-dependent fashion. Taken together, the data suggest that H. pylori senses microgravity as an environmental cue that triggers resistance to several kinds of stress. Other stresses will be investigated to improve understanding of how microgravity influences stress responses in pathogenic bacteria.

Microgravity-mediated resistance of Helicobacter pylori to stress

255th National Meeting (2018)

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