Bat Cutaneous Microbial Assemblage Functional Redundancy Across a Host-Mediated Disturbance

Abstract

Understanding the processes and factors that influence the structure of host-associated microbial assemblages has been a major area of research as these assemblages play a role in host defense against pathogens. Previous work has found that bacterial taxa within bat cutaneous microbial assemblages have antifungal capabilities against the emerging fungal pathogen, Pseudogymnoascus destructans. However, our understanding of natural fluctuations in these cutaneous microbial assemblages over time due to shifts in host habitat is lacking. The objective of this work was to understand how the taxonomic and functional bat cutaneous microbial assemblage responds to seasonal shifts in host habitat. We hypothesized that at the community level, there will be turnover in taxonomic structure but functional redundancy across seasons. On a finer scale, we hypothesized that there will be differences in the relative abundance of functional genes that code for select pathways across seasons. Results showed that, on a broad scale, the bat cutaneous microbial assemblage is seasonally taxonomically dynamic but functionally redundant. Additionally, although there was almost complete taxonomic turnover between winter and summer bat microbial assemblages, there was no difference in assemblage structure across winters. This functional redundancy was also observed at finer scales, with no differences in the abundance of genes within pathways of hypothesized importance across seasons or winters. Taken together, results suggest species sorting mechanisms correlated with shifts in host habitat use, drive taxonomic but not functional host-associated cutaneous microbial community assembly.

Keywords: Eptesicus fuscus; Community assembly; Host-microbe interactions; Microbial resilience; Microbiome.

Fig. 1

Non-metric multidimensional scaling ordination (NMDS) comparing taxonomic beta diversity of bat associated microbial assemblages across (A) season (stress = 0.12) and (B) winters (stress = 0.10). There is a significant difference in average assemblage structure across seasons (A; p < 0.05) but not across years (B; p > 0.05). (C) NMDS comparing functional beta diversity of bat associated microbial assemblages across season (stress = 0.06) and (D) winters (stress = 0.13). There is no significant difference in average functional assemblage structure across seasons (p > 0.05) and years (p > 0.05). (E) Distribution of sample locations, lighter-shaded counties were sampled in summer; darker counties were sampled in winter

Fig. 2

Comparison of relative abundance of genes within the pathways for protective functions (A) membrane transport across seasons, (B) membrane transport across years; (C) metabolism of terpenoids and polyketides across season, (D) metabolism of terpenoids and polyketides across years, (E) biosynthesis of secondary metabolites across seasons, and (F) biosynthesis of secondary metabolites across years. There were no significant differences in gene relative abundances across seasons or years

Fig. 3

Comparison of relative abundance of genes within the pathways for metabolic functions (A) glycolysis across seasons, (B) glycolysis across years, (C) sulfur metabolism across seasons, (D) sulfur metabolism across years, (E) oxidative phosphorylation across seasons, (F) oxidative phosphorylation across years, (G) methane metabolism across seasons, (H) methane metabolism across years. There were no statistically significant differences in gene abundance across seasons or years