Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/2006
Publication Date: 8/20/2006
Citation: Lehman, R.M., Lundgren, J.G., Chee Sanford, J.C. 2006. Discovery of stable microbial communities and investigation of their function within the guts of economically-important ground beetles. International Symposium on Microbial Ecology, Vienna, Austria, August 20-25, 2006. Interpretive Summary: Ground beetles are important components of biological control efforts in agricultural fields. Ground beetles consume pest insects and weed seeds. Initial studies indicate a role for bacterial symbionts in these agriculturally-beneficial processes. Research was conducted to explore the nature of this undiscovered relationship between ground beetle and microbial symbionts. DNA was extracted and genes diagnostic of bacterial species (16S rDNA) were amplified using the polymerase chain reaction from the intestinal tracts of three ground beetle species, Harpalus pensylvanicus, Anisodactylus sanctaecrucis, and Poecilus chalcites. Several type of molecular analyses performed on these amplified gene fragments indicate stable bacterial communities unique to each beetle species. Additional studies suggest a nutritional role in at least herbivorous beetles. Other roles (disease, pesticide resistance) are being explored.
Technical Abstract: Recent investigations of insect-associated microorganisms are revealing an array of microbe-insect relationships that extend well beyond those that have been previously studied (e.g., crickets, termites, etc.). We have examined the bacteria inhabiting the gut of economically-important ground beetles, Harpalus pensylvanicus, Anisodactylus sanctaecrucis, and Poecilus chalcites. These beetles are among those that are known to exhibit valuable pest management behavior such as weed seed consumption and predation of pest insects in agricultural settings. Molecular bacterial community profiling (16S rDNA tRFLP) has revealed that individual beetles of the same species (H. pensylvanicus or A. sanctaecrucis) possess relatively consistent bacterial populations. Clonal analyses (16S rDNA) has shown that the gut communities of these beetles are very simple, comprised of six and three bacterial species, respectively. Only one bacterial species, Hafnia alvei, was common to both beetle species, and it was the dominant community member (by clonal frequency) in both cases. Feeding studies conducted with these two granivorous beetles using weed seeds and antibiotic treatments suggest a nutritional role for gut bacteria. On the other hand, feeding studies with the predaceous beetle P. chalcites using cricket eggs and antibiotic treatments did not suggest a nutritional role for gut bacteria in this beetle species. Molecular analyses of cultured gut bacteria and DNA extracted directly from P. chalcites guts support investigations into potential functions such as disease and pesticide resistance.