Analysis of symbiosis among microbes forcused on a thermophilic symbiotic bacterium

点击翻译按钮获取中文摘要

We have analyzed the absolute symbiosis between symbiobacterium thermophilum (ST) and Bacillus strain S (BS) from the following two aspects.(I) Possible involvement of ptsl gene of Bacillus in the symbiosis.We have previously purified Ptsl protein from the cell extract of BS following its very weak growth-supporting activity for ST.We have performed expression and purification of recombinant Ptsl protein by E.coli system, and failed to detect it's ST-supporting activity. On the other hand, we have noticed that addition of glucose in the media completely inhibitted the growth of ST but not of BS, and further experiments showed that ptsl-deficient mutant supports the growth of ST even in the presence of glucose in the media. Therefore, we tentatively hypothesize that the growth supporting activity for ST by BS is under the control of catabolite repression, and ptsl is involved in the uptake of catabolites into the BS cells but not directly in the ST-supporting activity.(II) Distribution of ST in the natural environment.We have already postulated that ST exists widely in the natural habitat through our extensive screening. Simultaniously, we noticed that ST is frequently isolated from composts made from bovine excreta. Further results of screening with contents of digestive organs of several herbivorus animals showed the high possibillity that ST is one of rumen bactera. It agrees with the cellular and physiological features of ST.