罗氏沼虾(Macrobrachium rosenbergii)养殖池塘沉积物中细菌、硫酸盐还原菌和硫氧化菌的垂直分布特征

Vertical distribution of bacterial, sulfate-reducing and sulfur-oxidizing bacterial communities in sediment cores from freshwater prawn (Macrobrachium rosenbergii) aquaculture pond

摘要:

沉积物中微生物介导的硫循环在有机物分解和养分循环中发挥重要作用，但目前我们对水产养殖生态系统中的参与硫酸盐还原和硫氧化过程的微生物多样性及其调控机制仍知之甚少。【目的】探究硫酸盐还原菌(sulfate-reducing bacteria，SRB)和硫氧化菌(sulfur-oxidizing bacteria，SOB)的垂直分布特征及其主要的环境驱动因素。【方法】本研究利用高通量测序和荧光定量PCR (qPCR)分析了罗氏沼虾(Macrobrachium rosenbergii)养殖池塘沉积物表层(0–1 cm)、中层(10–11 cm)和底层(20–21 cm)中的细菌、SRB和SOB的丰度、多样性和群落组成。【结果】细菌(16S rRNA)、硫酸盐还原菌(dsrB)和硫氧化菌(soxB)的基因拷贝数呈现着从表层到中层急剧骤降的趋势(ANOVA，P<0.05)，但中层和底层样品之间的差异却并不显著(P>0.05)，以及α多样性分析显示3个群体的物种丰富度和均匀度都随深度而逐步降低，这都说明硫循环过程主要发生于沉积物的表层。γ-、δ-和β-变形菌分别是细菌、SRB和SOB的优势类群；其中SRB以Desulfobacca属和脱硫八叠球菌属(Desulfosarcina)为主，前者在表层有着最低的比重，而后者却与之相反；硫杆菌(Thiobacillus)作为细菌和SOB的优势属，更广泛地分布于中层沉积物中。RDA分析和Mantel检验揭示了影响细菌群落的主要环境因子是NO₃^–、SO₄^2–、TOC和TON，而SRB的群落变异主要是由As、TON、NO₃^–和Pb所驱动，以及SOB的群落变化则主要响应了TC、NO₂^–、NH₄⁺和TON浓度。【结论】养殖池塘底栖的细菌、SRB和SOB的丰度、多样性和群落结构的垂直分布特征可能受到多种环境因素共同的影响。

Abstract:

The sulfur cycle mediated by microbes in sediments plays an important role in the decomposition of organic matters and nutrient cycling. However, little is known about the microbial diversity and potential regulatory mechanisms involved in sulfate reduction and sulfur oxidation in aquaculture ecosystems. [Objective] To explore the vertical distribution pattern of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) and their environmental driving factors. [Methods] In this study, the abundance, diversity and community composition of bacteria, SRB and SOB in surface (0-1 cm), middle (10-11 cm) and bottom (20-21 cm) sediments originated from a freshwater prawn (Macrobrachium rosenbergii) aquaculture pond were investigated by high-throughput sequencing and real-time PCR (qPCR). [Results] The gene copy numbers of bacteria (16S rRNA), SRB (dsrB) and SOB (soxB) showed a trend of dramatic decline from the surface to the middle layer (analysis of variance, P<0.05), but the difference between the middle and bottom layers was not significant (P>0.05). The α-diversity analysis showed that species richness and evenness of three microbial populations both gradually decreased with depth, implying that the microbial sulfur cycling processes mainly occur on the surface layer. The γ-, δ- and β-proteobacteria were the dominant taxa of bacteria, SRB and SOB, respectively. Specifically, SRB was dominated by Desulfobacca and Desulfosarcina; the former has the lowest proportion in the surface layer, while the latter was the opposite. Thiobacillus, as the major genus of bacteria and SOB, was more abundant in the middle layer. Redundancy analysis and Mantel test revealed that the key environmental factors driving the variation of bacterial communities were NO₃^-, SO₄^2-, total organic carbon (TOC) and total organic nitrogen (TON), while the SRB community variation was mainly affected by arsenic (As), TON, NO₃^- and lead (Pb), and SOB responded to the changes in total carbon (TC), NO₂^-, NH₄⁺ and TON. [Conclusion] The abundance, diversity and community structure of bacteria, SRB and SOB in aquaculture pond sediment exhibited distinct vertical distributions, which could be driven by multiple environmental factors.