Inter- and intraspecific comparison of the bacterial assemblages in the hindgut of humivorous scarab beetle larvae (Pachnoda spp.)

Abstract

The larvae of scarab beetles are model organisms for studying the role of physicochemical gut conditions and intestinal microbiota in symbiotic digestion, particularly of humus. Here, we address the question of whether the enlarged hindgut paunch of Pachnoda ephippiata and Pachnoda marginata, two closely related, but allopatric species, harbors a specific bacterial microbiota. Terminal restriction length fragment polymorphism (T-RFLP) analysis revealed that in both species, the bacterial hindgut community differs strongly from that in the midgut, food soil, and fecal pellets. High intra- and interspecific similarities between the T-RFLP profiles of different larvae indicate the presence of a hindgut-specific microbiota. Nevertheless, we found a clear separation of the two species. A 16S rRNA gene clone library from the hindgut of P. ephippiata identified the major phylogenetic groups as members of the Clostridia, Betaproteobacteria, and Bacteroidetes, followed by Bacillales and Deltaproteobacteria. A comparison with a previously obtained clone library of the same species corroborates both the similarities and the intraspecific variance of the hindgut microbiota.