How host and microbial factors combine to structure gut microbial communities remains incompletely understood. Redox potential is an important environmental feature affected by both host and microbial actions. We assessed how antibiotics, which can impact host and microbial function, change redox state and how this contributes to post-antibiotic succession. We showed gut redox potential increased within hours of an antibiotic dose in mice. Host and microbial functioning changed under treatment, but shifts in redox potentials could be attributed specifically to bacterial suppression in a host-free ex vivo human gut microbiota model. Redox dynamics were linked to blooms of the bacterial family Enterobacteriaceae. Ecological succession to pre-treatment composition was associated with recovery of gut redox, but also required dispersal from unaffected gut communities. As bacterial competition for electron acceptors can be a key ecological factor structuring gut communities, these results support the potential for manipulating gut microbiota through managing bacterial respiration.

These findings support the hypothesis that abnormal gut microbial communities are a host factor related to V. cholerae susceptibility.

Background: How human-associated microbial communities resist and respond to perturbations remains incompletely understood. Viral challenge provides one opportunity to test how human microbiota respond to disturbance. Methods: Using an experimental human rhinovirus infection challenge model, we explored how viral infection may alter microbiota of the upper respiratory tract (URT). Healthy human volunteers were inoculated with HRV serotype 39. Samples were collected by lavage before and after inoculation from healthy (sham inoculated, n=7) and infected (n=15) individuals and subjected to 16S rRNA gene sequencing through amplification of the V4 hypervariable region. Results: No evidence for differences in community alpha-diversity between cohorts was observed. The composition of microbiota of sham-treated and infected subjects did not appear distinguishable and no taxa were significantly associated with infection status. We did not observe support for a correlation between microbial dynamics and counts of specific monocytes. Subject identity was found to be the strongest determinant of community structure in our dataset. Conclusions: Overall, our findings do not suggest a consistent nasopharyngeal microbiota response to rhinovirus challenge. We support the conclusion that this microbial community is individualized. Broadly, our findings contribute to our understanding of how and when immune responses to viruses affect bacterial communities in the URT.

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