LAUSR

To provide a foundation for the management of microbial fermentation beds, new resource mining of Bacillus⁃like species, and development of microbial agents, we investigated the spatial distribution pattern and community diversity of Bacillus⁃like species in the litters of a pig⁃on⁃litter system. The microbial fermentation bed was divided into 32 square areas of 4 rows × 8 columns. A sample from each area was obtained using a five⁃point sampling mode. Bacillus⁃like bacteria were isolated from the 32 samples using a culture method and preliminarily identified based on 16S rRNA gene sequences. The htt p:/ /w ww .ec olo gic a.c n http: / / www.ecologica.cn spatial distribution pattern of the Bacillus⁃like bacteria was analyzed using a concentration index and regression analysis. Moreover, the Shannon⁃Wiener diversity index, Simpson dominance index, Hill index, and richness were separately calculated to reveal the community structure and diversity of the Bacillus⁃like bacteria in the microbial fermentation bed. A total of 452 Bacillus⁃like isolates were obtained from the 32 litter samples, and identified as 48 species belonging to eight genera and two Families (Bacillaceae and Paenibacillaceae) within the Bacilli by 16S rRNA gene sequences. The species numbers for the genera were as follows: 30 for Bacillus, six for Lysinibacillus, five for Paenibacillus, three for Brevibacillus, and one for each of Ornithinibacillus, Oceanobacillus, Paucisalibacillus, and Gracilibacillus. There was a large difference in the distribution of Bacillus⁃like species in the fermentation bed. On the basis of their occurrence frequency, the Bacillus⁃like species could be discriminated as the widespread species, including Bacillus licheniformis; sparsely distributed species, including B. rhizosphaerae; and rare species, including B. flexus. According to the abundance of each species, the Bacillus⁃ like species could be classified into the high⁃content dominant populations, including B. licheniformis; medium⁃content common populations, including Lysinibacillus halotolerans; oligocontent oligo populations, including B. rhizosphaerae, and low⁃content occasional populations, including B. humi. The concentration class and regression analysis results indicated that the spatial distribution pattern of the Bacillus⁃like species in the microbial fermentation bed was an aggregated distribution. In the litters, the content range, total content, richness, Simpson index, Shannon⁃Wiener index, and Pielou′s evenness index of the Bacillus⁃like species were 0.01—94.1 × 10 cfu / g, 4.41 × 10 cfu / g, 0.4928, 0.2634, 1.3589, and 0.9803, respectively. Moreover, B. licheniformis appeared to have the highest Shannon⁃Wiener index value. On the basis of the diversity index cluster analysis, all the Bacillus⁃like species could be divided into a high richness high content group and a low richness low content group. The Bacillus⁃like bacteria can actively inhabit microbial fermentation beds and have rich species and abundant contents. Thus, the microbial fermentation bed can be considered as a natural bacterial “ fermentation tank,” which is expected to be directly used as a microbial inoculum and applied in the fields for purposes including soil improvement, crop disease prevention and control, and pollution management.