Diversity of the phoD Gene Encoding Alkaline Phosphatase in Sediment of Sancha Lake and Its Relationship with Environmental Factors

Abstract

The bacterial phoD gene encoding alkaline phosphatase (ALP) plays animportant role in the release of soluble reactive phosphorus (SRP) from organic phosphorus in environmental systems. However, phoD gene diversity in the sediments of the sub-deep freshwater lakes with eutrophication is poorly understood. In the present study, we sampled the sediments and the overlying water of Sancha Lake, a typical eutrophic sub-deep freshwater lake in China, in April (spring) and November (autumn), 2017. High-throughput sequencing and qPCR were performed to analyze the bacterial phoD gene in the sediments. The diversity and abundance of the phoD gene and the bacterial community structure based on this gene were characterized. We further discussed the relationships between the diversity and abundance of the phoD gene and environmental factors. A total of 881,717 valid sequences were obtained from 18 samples and were classified into 41 genera, 31 families, 23 orders, 12 classes, and 9 phyla and grouped into 477 OTUs. The dominant phyla were Proteobacteria and Actinobacteria. The phylogenetic tree based on the sequences of the phoD gene was plotted and composed of three branches. The genetic sequences were aligned predominantly with genera Pseudomonas, Streptomyces, Cupriavidus, and Paludisphaer. The phoD-harboring bacterial community structure showed a significant difference in spring and autumn, but no apparent spatial heterogeneity. Significant spatial heterogeneity and seasonal changes were observed in phoD gene abundance. pH value, dissolved oxygen (DO), total organic carbon (TOC), ALP, and phosphorus were important environmental factors affecting the diversity of the phoD gene and the phoD-harboring bacterial community structure. Changes in phoD-harboring bacterial community structure, phoD gene abundance, and ALP activity were negatively correlated with SRP in overlying water. Our study indicated phoD-harboring bacteria in the sediments of Sancha Lake with the characteristics of high diversity and significant spatial and temporal heterogeneity in abundance and community structure, which played a crucial role in the release of SRP.