Specificity between lactobacilli and hymenopteran hosts is the exception rather than the rule

Area of Science:

• Microbiology
• Entomology
• Evolutionary Biology

Background:

• Lactobacilli are common in food fermentation and probiotics, and are also found in the microbiota of social insects like ants, bees, and wasps.
• Honey bees and bumble bees are known to associate with host-specific lactobacilli, which are thought to be important for their health.
• Social transmission plays a role in maintaining these host-microbe associations.

Purpose of the Study:

• To investigate whether lactobacilli associated with social hymenopteran hosts are generally host-specific.
• To compare the host specificity of lactobacilli across different social Hymenoptera species.

Main Methods:

• Collected publicly available Lactobacillus 16S rRNA gene sequences.
• Utilized 454 pyrosequencing data from six hymenopteran species (three sweat bees, three ants).
• Determined comparative secondary structural models of 16S rRNA for accurate gene alignment and performed BLAST searches and phylogenetic reconstructions.

Main Results:

• Confirmed that honey bees and bumble bees have host-specific Lactobacillus associates.
• Found that sweat bees and ants associate with lactobacilli closely related to those from vertebrate hosts or diverse environments, irrespective of colony size or trophallaxis.
• Highlighted that the reasons for host-specific lactobacilli in honey and bumble bees, but not other social Hymenoptera, remain unclear.

Conclusions:

• Honey bees and bumble bees exhibit unique host-specific Lactobacillus associations compared to other social Hymenoptera like ants and sweat bees.
• Lactobacilli can inhibit other microbes and benefit hosts, whether coevolved or environmentally acquired.
• Further research is needed to understand the mechanisms driving these divergent host-microbe relationships in social insects.