Abstract
Nitrogen-fixingEnterobacter agglomerans andEnterobacter spp. were consistently isolated from the bark beetleDendroctonus 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 withD. terebrans suggests a symbiotic relationship. Nitrogen-fixing bacteria were also isolated from the bark beetlesDendroctonus frontalis andIps avulsus.