Gut microbiota of Pheretima heteropoda and allolobophorajaponica fed under the same laboratory conditions

Our previous study reported that the gut microbiota of Megascolecidae was distinguishable from that of Lumbricidae. In this study, two earthworms, Pheretima heteropoda (Megascolecidae) and Allolobophora japonica (Lumbricidae), were fed under the same in vitro conditions to investigate the effect of feed on gut microbiota. Their gut microbiota was analyzed by denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments. Most of the dominant bands were shared between both earthworm species, but some were specific to one species. These banding patterns corresponded to in situ earthworms, i.e. they were directly analyzed after collection from the field. The predominant bacterium found in P. heteropoda gut samples was Bacillus longiquaesitum (AM747042)-related, whereas the predominant bacteria found in A. japonica gut samples were bacterium TG141 (AB308367)-related and Rhizobium sp. BBCT66 (DQ337551)-related. These results indicated that the major bacterial species were not influenced by the surrounding environment, including the food source, even though a large portion of the bacterial population was opportunistic.