Navarro-Diaz, M. | bioRxiv Science

bioRxiv2025

Tyrosine availability shapes Staphylococcus aureus nasal colonization and interactions with commensal communities

Only certain individuals are nasally colonized by Staphylococcus aureus, making them more susceptible to developing endogenous infections. The role of the resident microbiota in modulating S. aureus nasal colonization remains largely unclear. Using a newly assembled nasal strain collection, we demonstrate that nasal commensals can either promote or inhibit S. aureus proliferation through strain- and community-specific effects in vitro and within gnotobiotic animals. We identified nutrient-dependent interactions as a key driver of these dynamics and found that S. aureus strains auxotrophic to tyrosine rely on amino acid-providing nasal communities to thrive in the nutrient-limited environment of the nose. Large-scale screenings revealed tyrosine dependency to affect 8% of nasal S. aureus strains and to impair S. aureus colonization. Our findings uncover a crucial factor in S. aureus physiology and its interactions as a commensal nasal species, paving the way for new decolonization strategies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/651429v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@17b6289org.highwire.dtl.DTLVardef@182249forg.highwire.dtl.DTLVardef@1324dc1org.highwire.dtl.DTLVardef@18ec3bf_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Variations in microbial diversity affect the stability and function of dark fermentation bioreactors

The relationship between the taxonomic diversity and the function of microbial communities is complex. Specifically, the ecological mechanisms that drive the dynamics of microbial populations and the consequences of these dynamics on functional traits have remained elusive. Among the simplest but natural microbial communities are dark fermentation consortia, a subset of the more diverse and complex microbial communities, anaerobic digestion communities. Dark fermentation consortia have been of interest as they produce biofuels such as hydrogen and different alcohols that can be used as fossil fuels alternatives. However, these hydrogen-producing communities have unresolved instability and low yield issues. We have previously proposed that instability and low yields in dark fermentation communities could be due to reduced diversity that results from aggressive pretreatments of original anaerobic digestion communities. In this work, we used dark fermentation communities to examine experimentally the effect of diversity reduction in functional traits, including stability and microbial interactions. We established two types of treatment, (i) maintaining strict culture conditions that are known to induce hydrogen production and ii) applying a heat-shock treatment known for selecting hydrogen-producing bacteria, which resulted in two types of communities, high and low diversity. Each treatment consisted of 12 replicates that were transferred to fresh medium daily (during 28 days for the non-treated bioreactors and 61 days for the heat-shock treated bioreactors). Microbial communities of the two treatments were characterized in their function as well as resistance to invasion. Microbial composition was characterized by culture-independent 16S rRNA gene amplicon sequencing. We analyzed microbial community composition and function through time, establishing statistical relationships between bacterial groups and metabolite production. Also, we inferred the potential ecological interactions that might have been established. Results show that the replicate bioreactors for each treatment predictably shifted to a similar composition and increased and stable biogas production. The non-treated bioreactors showed less susceptibility to the invasion (with the invasive bacteria establishing only in one replicate in the non-treated bioreactors vs 6 invaded replicates of the heat-shock treated bioreactors). However, the effect observed in the non-treated bioreactor replicate where the invader bacteria established was more drastic since the invasive bacteria managed to become dominant.

ecology↗