The symbiotic relationship between microorganisms and their host is recognised to influence the fitness and health of many insect species. Microbial populations associated with honey bees have been extensively characterized. Therefore, we will discuss the similarities and differences with those of other managed and wild bees, which have been studied to a lesser extent. The microbiota of wild bees was examined in the studies performed worldwide, highlighting variations in the composition according to the bee taxonomy and geographical origin. The mediation of social interactions in symbiont transmission, as well as environmental transmission pathways are discussed in relation to bacterial diversity in eusocial and solitary bees. The role of bacterial symbionts in promoting bee survival is presented, both in biotic and abiotic stress conditions, reporting different case studies.