Correlations of functional genes involved in methane, nitrogen and sulfur cycling in river sediments

Abstract

Microorganisms in sediments play an important role in carbon (C)- , nitrogen (N)- and sulfur (S)-cycles by regulating forms and contents of these elements. The coupled system or synergistic reaction between these elemental cycles could effectively alleviate the pollution of C, N, and S in sediments. However, little is known about the indicators indicating the coupled system in surface sediments. We hypothesized that the correlations of functional genes could be used as a reference index speculating the coupled systems of C-N-S in this study. Here, 135 sediment samples from Huaihe River Basin in Northern Anhui Province were collected. To test this hypothesis, we investigated the relationships of C, N, S-functional genes, the co-occurrence analysis of microbial functional groups and the contributions of functional genes to nutrients. The findings revealed that the synergetic relationships between raw or predicted genes could speculate the coupled systems. The network analysis of microbial co-occurrence patterns also implied the occurrence of coupled processes. Moreover, the results shed light on the important role of Desulfobacterium and Methanosaeta. This hypothesis was further underpinned by the dominant prediction of the C- and S-functional genes on the nitrogen nutrition. Taken together, we could concluded that that the sulfate-reducing gene (aprA) and the methanogenic gene (mcrA) played a major role in the coupled processes in the elemental biogeochemical cycle. This study provided a valuable reference for predicting the coupled metabolism of river sediments.