Dynamic Change in Enzyme Activity and Bacterial Community with long-term rice Cultivation in Mudflats

Bacteria play an important role in the reclamation of mudflats. However, little is known about the effects of long-term rice cultivation on bacterial communities in mudflats. In this study, the bacterial community in mudflats with long-term rice cultivation was evaluated using Illumina MiSeq sequencing of the bacterial 16S rRNA genes. We found that the soil enzyme activity in mudflat soil demonstrated an overall increasing trend with an increase in rice planting years, while polyphenol oxidase activity decreased. There were significant differences in the microbial community composition between mudflat and paddy soil. There were high proportions of Proteobacteria and Bacteroidetes in mudflat soil, while the predominant phyla in paddy soil were Proteobacteria, Chloroflexi, and Acidobacteria. The dominant taxa were significantly correlated with electrical conductivity, organic matter, and total nitrogen. In addition, the proportion of Fe- and S-related bacteria in paddy soil was much higher than that of mudflat soil, including Anaeromyxobacter, Geobacter, Thiobacillus, Clostridium, and GOUTA19. Furthermore, the proportion of some nitrogen cycle-related bacteria (e.g., Nitrospira, Steroidobacter, Rhodoplanes) and some carbohydrate-degrading bacteria (e.g., Anaerolinea, Candidatus Solibacter) also increased with long-term rice cultivation in mudflat soil. These key microbial players are involved in the biogeochemical C, N, S, and Fe cycles of mudflat paddy soil during mudflat reclamation by rice cultivation. In short, the orderly succession of the bacterial community changed with the change of soil physical-chemical properties during long-term rice cultivation. In addition, key microbial players have a beneficial ecological function in enhancing soil fertility.