Abstract

Cultivation-independent techniques like PCR-amplified restriction fragment length polymorphism (PCR-RFLP) of 16S rRNA genes and real-time PCR were applied to assess the abundance, diversity and phylogenetic composition of Anaeromyxobacter communities over time in flooded, unplanted paddy soil slurries. Six Anaeromyxobacter communities were sampled from anoxic slurries at 1 h, and 1, 5, 10, 20 and 30 days while the Fe (II) concentrations were measured also. Bacterial Genomic DNA was extracted and PCR-amplified to obtain 16S rDNA fragments of Anaeromyxobacter which were cloned to construct 6 16s rDNA libraries. Eventually 10 major Anaeromyxobacter types were identified by RFLP fingerprintings. Results showed that the optimal increasing phase of Fe (II) was from 1h to nearly 10 days, being correspond with the growth phase of the abundance of Anaeromyxobacter. The highest diversity appeared in slurry at 30 days and the lowest was found at 30 days. Jackknife Environment Clusters by UniFrac showed that phylogenetic compositions of Anaeromyxobacter communities in slurries at 10 and 20 days were the most similar. By evolutionary distance analysis, our 10 major Anaeromyxobacter types were diverged into Group 1 and 2 in phylogenetic tree, while Group 1 was the exclusive collection of clones from our experiment. Major type P1 was present in all slurries abundantly and P9 only existed in slurry at 5 days. The abundance of Anaeromyxobacter spp., calculated as its proportion of 16S rDNA copies to the value of total Bacteria, was from 0.242% at 1 h to 5.135% at 10 days. We demonstrated that flooding time led to successional dynamics of major types and variable abundance of Anaeromyxobacter community. Flooding time also influenced the diversity of Anaeromyxobacter community on some extent. Canonical correspondence analysis (CCA) revealed that Anaeromyxobacteria spp. abundance had interrelation with Fe (II) content and the influenced the distribution of the slurries in the Biplot. Moreover, our study provides valuable information for the further isolation of Anaeromyxobacter strains from paddies.

Key words: Anaeromyxobacter; paddy soil, community structure, abundance, PCR-RFLP, flooding time.