Flowers and Wild Megachilid Bees Share Microbes

Abstract

Transmission pathways have fundamental influence on microbial symbiont persistence and evolution. For example, the core gut microbiome of honey bees is transmitted socially and via hive surfaces, but some non-core bacteria associated with honey bees are also found on flowers, and these bacteria may therefore be transmitted indirectly between bees via flowers. Here, we test whether multiple flower and wild megachilid bee species share microbes, which would suggest that flowers may act as hubs of microbial transmission. We sampled the microbiomes of flowers (either bagged to exclude bees or open to allow bee visitation), adults, and larvae of seven megachilid bee species and their pollen provisions. We found a Lactobacillus operational taxonomic unit (OTU) in all samples but in the highest relative and absolute abundances in adult and larval bee guts and pollen provisions. The presence of the same bacterial types in open and bagged flowers, pollen provisions, and bees supports the hypothesis that flowers act as hubs of transmission of these bacteria between bees. The presence of bee-associated bacteria in flowers that have not been visited by bees suggests that these bacteria may also be transmitted to flowers via plant surfaces, the air, or minute insect vectors such as thrips. Phylogenetic analyses of nearly full-length 16S rRNA gene sequences indicated that the Lactobacillus OTU dominating in flower- and megachilid-associated microbiomes is monophyletic, and we propose the name Lactobacillus micheneri sp. nov. for this bacterium.

Insect exclusion limits variation in bacterial microbiomes of tomato flowers and fruit

“…In fact, it has been suggested that flowers act as bacterial hubs for bees (McFrederick et al . ). The less dramatic effect observed in our study could be explained by the structure of the tomato flower.…”

Habitat and indigenous gut microbes contribute to the plasticity of gut microbiome in oriental river prawn during rapid environmental change

“…Studies of other arthropod animals indicate that transmission pathways have fundamental influence on microbial symbiont persistence and evolution. For example, bees may acquire certain putative probiotics through maternal inheritance (vertical transmission) [52], while the core gut microbiome of honey bees is transmitted socially via hive surfaces [53], and the initial establishment of symbiotic gut bacteria in the turtle ant occurs after pupation via oral-rectal trophallaxis [54]. The shrimp usually care for the fertilized eggs, however the eggs are also exposed to environmental water with microbes, and the mechanism of selecting indigenous gut microbes might be the key to answer the inheritance of gut microbes in shrimp.…”

Linking pollen foraging of megachilid bees to their nest bacterial microbiota

“…On the other hand, solitary bee nests harbor highly diverse bacterial communities (Keller, Grimmer, & Steffan‐Dewenter, ; Lozo et al, ; McFrederick & Rehan, ; Mohr & Tebbe, ; Voulgari‐Kokota, Grimmer, Steffan‐Dewenter, & Keller, ). However, only few studies have dealt with their role in larval health (Keller et al, ; McFrederick, Vuong, & Rothman, ) or their acquisition routes (McFrederick et al, ; Voulgari‐Kokota, McFrederick, Steffan‐Dewenter, & Keller, ). Bees leading a solitary lifestyle with no direct contact between multiple generations are excluded from the benefits of a social structure, where individuals are in constant interaction with their nestmates, and their nest microbiota is more susceptible to environmentally introduced bacteria (Keller et al, ; McFrederick et al, ; Rothman, Andrikopoulos, Cox‐Foster, & McFrederick, ; Voulgari‐Kokota, Grimmer, et al, ; Voulgari‐Kokota, McFrederick, et al, ).…”

“…However, only few studies have dealt with their role in larval health (Keller et al, ; McFrederick, Vuong, & Rothman, ) or their acquisition routes (McFrederick et al, ; Voulgari‐Kokota, McFrederick, Steffan‐Dewenter, & Keller, ). Bees leading a solitary lifestyle with no direct contact between multiple generations are excluded from the benefits of a social structure, where individuals are in constant interaction with their nestmates, and their nest microbiota is more susceptible to environmentally introduced bacteria (Keller et al, ; McFrederick et al, ; Rothman, Andrikopoulos, Cox‐Foster, & McFrederick, ; Voulgari‐Kokota, Grimmer, et al, ; Voulgari‐Kokota, McFrederick, et al, ). As a result, the establishment of steady host–microbe interactions requires different mechanisms and could be the result of more complex processes, where beneficial microbial interactions are reinforced and negative interactions with pathogens are minimized.…”

“…These should be able to secure transmission routes over multiple generations through active and passive transmission. Three possible mechanisms are active inoculation of nest structures (as in Kaltenpoth, Yildirim, Gürbüz, Herzner, & Strohm, ) including stored pollen, active inoculation of eggs (Hosokawa, Kikuchi, & Fukatsu, ), or passive transmission through imported materials and especially food sources (McFrederick & Rehan, ; McFrederick et al, ; Rothman et al, ).…”