Dolosigranulum pigrum cooperation and competition in human nasal microbiota

Abstract

BackgroundMultiple epidemiological studies identify Dolosigranulum pigrum as a candidate beneficial bacterium based on its positive association with health, including negative associations with nasal/nasopharyngeal colonization by the pathogenic species Staphylococcus aureus and Streptococcus pneumoniae. ResultsUsing a multipronged approach to gain new insights into D. pigrum function, we observed phenotypic interactions and predictions of genomic capacity that support a role for microbe-microbe interactions involving D. pigrum in shaping the composition of human nasal microbiota. We identified in vivo community-level and in vitro phenotypic cooperation by specific nasal Corynebacterium species. Also, D. pigrum inhibited S. aureus growth in vitro. Whereas, robust inhibition of S. pneumoniae required both D. pigrum and a nasal Corynebacterium together, and not either alone. D. pigrum L-lactic-acid production was insufficient to account for these inhibitions. Genomic analysis of 11 strains revealed that D. pigrum has a small genome (average 1.86 Mb) and multiple predicted auxotrophies consistent with D. pigrum relying on its human host and cocolonizing bacteria for key nutrients. Further, the accessory genome of D. pigrum encoded a diverse repertoire of biosynthetic gene clusters, some of which may have a role in microbe-microbe interactions. ConclusionsThese new insights into D. pigrums functions advance the field from compositional analysis to genomic and phenotypic experimentation on a potentially beneficial bacterial resident of the human upper respiratory tract and lay the foundation for future animal and clinical experiments.