Abstract
Nitrogen-fixing Enterobacter agglomerans and Enterobacter spp. were consistently isolated from the bark beetle Dendroctonus terebrans. Large populations of nitrogen-fixing bacteria were found with the beetle, although no in situ acetylene reduction was demonstrated. The constant occurrence of nitrogenfixing bacteria with D. terebrans suggests a symbiotic relationship. Nitrogen-fixing bacteria were also isolated from the bark beetles Dendroctonus frontalis and Ips avulsus.