Submitted to: MicrobiologyOpen
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/29/2014
Publication Date: 6/24/2014
Citation: Blackburn, M.B., Martin, P.A., Kuhar, D.J., Farrar, R.R., Gundersen, D.E. 2014. Crystalliferous Bacillus cereus group bacteria from a Maryland hardwood forest are dominated by psychrotolerant strains. MicrobiologyOpen. DOI:10.1002/mbo3.189. Interpretive Summary: Varieties or strains of the insect killing bacterium Bt are always selected based on how toxic they are to the insect. Other features that might improve their usefulness, such as their ability to persist or grow in areas where they are applied, have not been investigated. Since Bt is often applied to hardwood forests in the Mid-Atlantic region to control gypsy moth, we investigated what types of Bt actually grow in such environments. Surprisingly, we found that most of the Bts present in soil from a central Maryland mixed hardwood forest were not closely related to the type usually applied for gypsy moth control. Instead, they represented several distinct varieties that are adapted to grow at low temperatures (<7°C). Very few examples of Bts related to commercial varieties were found. Although the cold-adapted Bts were not as toxic to gypsy moth as commercial varieties, they might persist in the forest environment more effectively. These results will be of interest to those searching for new microbes for insect control, and those studying the ecology of bacteria related to Bt.
Technical Abstract: Crystal forming Bacillus spp. were isolated from soil samples collected at different elevations within a mixed hardwood forest in central Maryland, and their phylogenetic relationships determined by multilocus sequence analysis. The vast majority of isolates obtained were associated with two phylogenetic groups known to be psychrotolerant, Groups II and VI of Guinebretière et al. 2008, with very few isolates representing phylogenetic groups more typically associated with Bt. Isolates from these groups were confirmed to be psychrotolerant by growth on solid media at 7°C. Isolates of 11highly related, novel sequence types from Group VI were generally found at higher elevations and not associated with soils near streams, while isolates of 2 related sequence types from Group II were nearly always found at the bottoms of ravines near streams.