ARS | Publication request: Manipulation of the Gut Bacterial Community in a Ground Beetle, Harpalus pensylvanicus, Influences its Feeding Behavior

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2010
Publication Date: March 26, 2010
Citation: Lehman, R.M., Lundgren, J.G. 2010. Manipulation of the Gut Bacterial Community in a Ground Beetle, Harpalus pensylvanicus, Influences its Feeding Behavior. American Society for Microbiology, San Diego CA, May 23-27, 2010.

Technical Abstract: Functional roles of non-obligatory bacterial symbionts found in the gut of insects are not well-described. We have found that the intestinal tract of an omnivorous ground beetle, Harpalus pensylvanicus, is colonized by relatively few bacterial species (six to nine species) that are common among field collected beetles. We manipulated the relative abundance of these gut bacteria during laboratory rearing by antibiotic treatment (with and without) and by diet (cricket eggs or weed seeds). According to tRFLP (16S rRNA gene) analysis of the gut bacteria, antibiotic-treated beetles showed a reduction in bacterial species richness and shifts in the relative abundance of bacterial species regardless of diet. However, the antibiotic-treated beetles fed cricket eggs maintained their consumption rates, while those fed weed seeds consumed significantly less seeds. Combining 16S rRNA gene sequence analysis of clone libraries with the tRFLP data, we were able to link the presence of one bacterial species, Enterococcus faecalis, with the number of seeds consumed by individual beetles. We propose that E. faecalis has a nutritional role in the insect gut, perhaps fermenting cellulosic sugars to organic acids as it is known to do in other settings. This research advances the understanding of bacterial-insect ecological relationships using ground beetles (H. pensylvanicus) that are beneficial in agroecosystems where they contribute to the control of insect and weed pests.