Single-step genome engineering in the bee gut symbiont Snodgrassella alvi

Host specificity of gut microbiota associated with social bees: patterns and processes

SUMMARYGut microbes provide benefits to some animals, but their distribution and effects across diverse hosts are still poorly described. There is accumulating evidence for host specificity (i.e., a pattern where different microbes tend to associate with distinct host lineages), but the causes and consequences of this pattern are unclear. Combining experimental tests in the laboratory with broad surveys in the wild is a promising approach to gaining a comprehensive and mechanistic understanding of host specificity prevalence, origin, and importance. Social bees represent an ideal testbed for this endeavor because they are phylogenetically and functionally diverse, with host-specific, stable, and tractable gut microbiota. Furthermore, the western honeybee (Apis mellifera) is an emerging experimental model system for studying microbiota-host interactions. In this review, we summarize data on the prevalence and strength of host specificity of the social bee gut microbiota (bumblebees, stingless bees, and honeybees), as well as the potential and proven ecological and molecular mechanisms that maintain host specificity. Overall, we found that host specificity in bees is relatively strong and likely results from several processes, including host filtering mediated by the immune system and priority effects. However, more research is needed across multiple social bee species to confirm these findings. To help future research, we summarize emerging hypotheses in the field and propose several experimental and comparative tests. Finally, we conclude this review by highlighting the need to understand how host specificity can influence host health.

Glyphosate effects on growth and biofilm formation in bee gut symbionts and diverse associated bacteria

Biofilm formation is a common adaptation enabling bacteria to thrive in various environments and withstand external pressures. In the context of host-microbe interactions, biofilms play vital roles in establishing microbiomes associated with animals and plants and are used by opportunistic microbes to facilitate survival within hosts. Investigating biofilm dynamics, composition, and responses to environmental stressors is crucial for understanding microbial community assembly and biofilm regulation in health and disease. In this study, we explore in vivo colonization and in vitro biofilm formation abilities of core members of the honey bee (Apis mellifera) gut microbiota. Additionally, we assess the impact of glyphosate, a widely used herbicide with antimicrobial properties, and a glyphosate-based herbicide formulation on growth and biofilm formation in bee gut symbionts as well as in other biofilm-forming bacteria associated with diverse animals and plants. Our results demonstrate that several strains of core bee gut bacterial species can colonize the bee gut, which probably depends on their ability to form biofilms. Furthermore, glyphosate exposure elicits variable effects on bacterial growth and biofilm formation. In some instances, the effects correlate with the bacteria's ability to encode a susceptible or tolerant version of the enzyme inhibited by glyphosate in the shikimate pathway. However, in other instances, no such correlation is observed. Testing the herbicide formulation further complicates comparisons, as results often diverge from glyphosate exposure alone, suggesting that co-formulants influence bacterial growth and biofilm formation. These findings highlight the nuanced impacts of environmental stressors on microbial biofilms, with both ecological and host health-related implications.

IMPORTANCE

Biofilms are essential for microbial communities to establish and thrive in diverse environments. In the honey bee gut, the core microbiota member Snodgrassella alvi forms biofilms, potentially aiding the establishment of other members and promoting interactions with the host. In this study, we show that specific strains of other core members, including Bifidobacterium, Bombilactobacillus, Gilliamella, and Lactobacillus, also form biofilms in vitro. We then examine the impact of glyphosate, a widely used herbicide that can disrupt the bee microbiota, on bacterial growth and biofilm formation. Our findings demonstrate the diverse effects of glyphosate on biofilm formation, ranging from inhibition to enhancement, reflecting observations in other beneficial or pathogenic bacteria associated with animals and plants. Thus, glyphosate exposure may influence bacterial growth and biofilm formation, potentially shaping microbial establishment on host surfaces and impacting health outcomes.