Bacterial Communities within Digestive Tracts of Ground Beetles (Coleoptera: Carabidae)

Abstract

We identified the bacterial communities within the alimentary tracts of two granivorous ground beetles as a first step in the exploration of bacteria–ground beetle symbioses. Terminal-restriction fragment length polymorphism analyses of bacterial rRNA extracted from the guts of field-collected individuals of Harpalus pensylvanicus (DeGeer) and Anisodactylus sanctaecrucis (F.) (Coleoptera: Carabidae) revealed that gut-associated bacterial communities were of low diversity. Individuals from the same beetle species possessed similar bacterial community profiles, but the two species exhibited unique profiles. Bacterial 16S rRNA clone libraries constructed for the two beetle species showed that H. pensylvanicus had a more diverse community (six operational taxonomic units [OTUs]) compared with A. sanctaecrucis (three OTUs). Only one OTU, closely related to Hafnia alvei , was common between the two beetle species. Cloned partial 16S rRNA sequences for each OTU were most closely matched to the following cultivated bacteria: Serratia sp., Burkholderia fungorum , and H. alvei and Phenylbacterium sp., Caedibacter sp., Spiroplasma sp., Enterobacter strain B-14, and Weissella viridescens , representing the divisions Alpha-, Beta- and Gammaproteobacteria, Mollicutes, and Bacilli. Some, but not all of these organisms have been previously associated with insects. The identification of bacteria uniquely and consistently associated with these ground beetles provides the basis for further investigation of species-specific functional roles.