| Bacillus is one of the best characterized bacterial genera. It is defined as a gram-positive, rod-shaped bacterium which can be aerobic or facultative anaerobic. Bacillus can produce highly resistant dormant endospores in response to nutritional or environmental stresses. Since the late 19t h century, the long history of Bacilli research has included classical microbiology, biochemistry, and more modern genomic and proteomic approaches. Flooded rice field has become a model system for the study of soil microbial ecology. In this study, the total DNA was extracted from six paddy soil slurries including 1 h, 1 d, 5 d, 10 d, 20 d and 30 d of flooding incubation. The changing characteristics of community diversity and succession of Bacillus were analyzed by using Denatured Gradient Gel Electrophoresis（DGGE） based on 16S rRNA gene（rDNA） of Bacillus. The influence factors on characteristics of community diversity and succession of Bacillus in different flooding treatments were analyzed by Detrended Canonial Correspondence Analysis（DCCA） and Canonical Correspondence Analysis（CCA）. It showed that the Bacillus community structure was taken place the successive changes under different flooding times. The R-strategists organisms dominated in the early succession, while the K-strategists organisms gradually replaced them in the late succession. At the early stage of incubation（1 h~1 d）, the similarity coefficient indices of predominant Bacillus were relatively high but the variety of diversity indices were low; during 1 d and 5 d, the diversity index changed more; during the later stage of incubation（20~30 d）, there were the highest similarity coefficient indices and diversity indices kept invariableness. The flooding process could be divided into three different ecotopes including early-stage, mid-stage and later-stage, on the basis of DCCA. Further more, the CCA ordination among DGGE profiles and environmental variable factors demonstrated that Fe（Ⅱ） concentration and the changes of diversity and richness of Bacillus correlated with the above three ecotopes. From the phylogenetic tree, we found that the nine preponderant DGGE bands belonged to Bacillus except of the HZ-B1 band divided into Paenibacillus sp.. Most of them had close relations with Bacillus sp. isolated from paddy soil fields. |
