Spatially explicit depiction of a floral epiphytic bacterial community reveals role for environmental filtering within petals

Abstract

The microbiome of flowers (anthosphere) is an understudied compartment of the plant microbiome. Within the flower, petals represent a heterogeneous environment for microbes in terms of resources and environmental stress. Yet, little is known of drivers of structure and function of the epiphytic microbial community at the within‐petal scale. We characterized the petal microbiome in two co‐flowering plants that differ in the pattern of ultraviolet (UV) absorption along their petals. Bacterial communities were similar between plant hosts, with only rare phylogenetically distant species contributing to differences. The epiphyte community was highly culturable (75% of families) lending confidence in the spatially explicit isolation and characterization of bacteria. In one host, petals were heterogeneous in UV absorption along their length, and in these, there was a negative relationship between growth rate and position on the petal, as well as lower UV tolerance in strains isolated from the UV‐absorbing base than from UV reflecting tip. A similar pattern was not seen in microbes isolated from a second host whose petals had uniform patterning along their length. Across strains, the variation in carbon usage and chemical tolerance followed common phylogenetic patterns. This work highlights the value of petals for spatially explicit explorations of bacteria of the anthosphere.

Divergent assembly processes? A comparison of the plant and soil microbiome with plant communities in a glacier forefield

“… 2012 ; Hayes et al . 2021 ), whereas a one-square-meter plot may be a rather homogeneous niche for plants. Likewise, a soil particle is characterized by a strong gradient of abiotic variables and thus provides various niches (Sexstone et al .…”

Divergent assembly trajectories: a comparison of the plant and soil microbiome with plant communities in a glacier forefield

“…Sampling a single leaf or petal means integrating over multiple microbial niches characterized by different availabilities of water, nutrients, and plant metabolites (Karamanoli et al, 2012, Hayes et al, 2021, whereas a one-square-meter-plot may be a rather homogenous niche for plants. Likewise, a soil particle is characterized by a strong gradient of abiotic variables and thus provides various niches (Sexstone et al, 1985).…”

Pollinators mediate floral microbial diversity and microbial network under agrochemical disturbance

“…Microbial dispersal via bees, the most important pollinators of cultivated strawberry (Klatt et al, 2014), can be potentially extensive and thus increase α-diversity (e.g., in bacterial communities), but high rates of microbial dispersal can also homogenize microbial communities, thereby contributing little to community differentiation (along cPCoA1) relative to other functional groups (Figure 4c,d). We found that bacterial taxa associated with bee visitation (post-hoc tests, Appendix S1; Table S7) often belong to Acinetobacter (including A. nectaris), Methylobacterium, Rosenbergiella and Sphingomonas, which are common in nectar (Pozo et al, 2014) and flowers (Hayes et al, 2021;Wei & Ashman, 2018). Relative to bees, the effect of visitation by true bugs and flies on microbial community differentiation may reflect microbial dispersal limitation mediated by these abundant functional groups.…”

“…whereas other microbes (Table S7) may be opportunistic or proliferate on flowers via mechanisms yet to be explored. Overall, the direct and indirect effects of flower abundance underlined the importance of considering this driver in the principles of microbiome assembly in flowers, in addition to other floral traits (e.g., volatiles, ultraviolet patterns; Hayes et al, 2021;Schaeffer et al, 2019).…”

“…Floral traits can influence the floral microbiome directly by affecting niche availability and imposing habitat filtering for microbes (Hayes et al, 2021;Vannette, 2020;Wei & Ashman, 2018) and indirectly by affecting pollinator visits (Armbruster, 2017;Kantsa et al, 2018;Wei et al, 2020) that can mediate microbial dispersal. In particular, flower abundance has rarely been studied in the floral microbiome but can potentially influence a given flower's microbial community by affecting the source pool of microbes hosted by neighbouring flowers (Toju et al, 2018).…”