Bacterial communities in Solenopsis invicta and Solenopsis geminata (Hymenoptera: Formicidae) colonies characterized by 16S-amplicon 454 pyrosequencing

Social insects harbor diverse communities of bacterial microbes, and these microbes may play a crucial role in the success or failure of biological invasions. The invasive fire ant Solenopsis invicta is a model system to understand the dynamics of invasive social insects and their biological control. However, little is known about microbes as biotic factors influencing success or failure of the invasion. This study is the first attempt to characterize microbial communities associated with introduced S. invicta and native S. geminata populations. Using 16S-amplicon 454-pyrosequencing, we compared bacterial communities on workers, on brood, and in the nest chambers in neighboring S. invicta and S. geminata colonies at Brackenridge Field Laboratory, Austin, Texas, with the aim of identifying potential pathogenic, commensal, and mutualistic microbial associates that may modulate the ecological success of these ant species. Two samples of S. geminata contained high levels of Spiroplasma, a pathogen of other insects, but only one S. invicta sample contained a low level of this microbe. One colony of S. invicta had a high count of Lactococcus. Generally, both ant species had much lower microbial diversity than surrounding soil, and both species had similar overall diversities although little overlap in specific microbes.