Dynamics of sulfate reduction and sulfate-reducing prokaryotes in anaerobic paddy soil amended with rice straw

Abstract

Incorporation of rice straw to soil is a common agricultural practice in rice cultivation. In anaerobic paddy soil, the complete mineralization of organic matter to CH 4 and CO 2 is accomplished by the sequential reduction of nitrate, ferric iron, sulfate, and methanogenesis. In order to estimate the temporal changes of sulfate-reducing prokaryotes (SRP) as decomposers of organic matters, the effects of rice straw amendment on the dynamics of sulfate reduction and SRP were investigated by combining the monitoring of CH 4 , sulfate, and organic acids with molecular tools such as soil DNA extraction, real-time PCR, cloning, sequencing, and phylogenetic analysis. The incorporation of rice straw into paddy soil significantly increased concentrations of sulfate, formate, acetate, propionate, and lactate and CH 4 production. The rate of sulfate reduction in the straw-amended slurries was significantly higher than that in the unamended slurries. The dsrAB gene copy numbers of SRP in the straw-amended soil slurries ranged from 4.26×10 6 to 1.96×10 8 per gram of dry soil, which were significantly higher than those in the unamended control ranging from 1.99×10 6 to 7.90×10 7 per gram of dry soil. Significant correlations were observed between SRP dsrAB gene copy numbers and the concentrations of sulfate and acetate. Cloning and sequencing analyses showed a clear shift of SRP community structure between treatments and time.In the straw-amended slurries, Clostridia-like SRP significantly increased, while Deltaproterobacteria-like SRP (Sytrophobacter, Desulfobacterium, Desulfovibrio, and Desulfomonile) decreased during the incubation period. Novel uncultured SRP were abundant in the straw-amended slurries and changed during the incubation period.

Phylogenetic diversity of Fe(III)-reducing microorganisms in rice paddy soil: enrichment cultures with different short-chain fatty acids as electron donors

“…In paddy soils, acetate, formate, and propionate are the primary short-chain fatty acids produced during residue decomposition (Krylova et al 1997;Yao and Conrad 2001;Rui et al 2009;He et al 2010). Citrate and succinate are exuded from rice roots (Aulakh et al 2001;Hoffland et al 2006).…”

Syntrophobacteraceae‐affiliated species are major propionate‐degrading sulfate reducers in paddy soil

“…However, it remains unknown which microbial groups are responsible for the consumption of propionate when sulfate is available. Species affiliated with Syntrophobacteraceae, Desulfobacteraceae, Desulfobulbaceae and Peptococcaceae, which have all been detected in paddy soils (Wind et al, 1999;Scheid et al, 2004;Stubner, 2004;He et al, 2010;W€ orner et al, 2016), are capable of using propionate as electron donor for sulfate reduction (Rabus et al, 2013). Nevertheless, their relative contributions and specific functions in propionate dependent sulfate reduction have not been studied.…”

Linkage between community diversity of sulfate-reducing microorganisms and methylmercury concentration in paddy soil

“…Sulfate-reducing microorganisms (SRM) is a phylogenetically diverse microbial group that contributes important function in soil including sulfate reduction, terminal oxidation of organic carbon, Hg methylation, and biodegradation of organic pollutants in anaerobic environments (Coates et al 1996;Dhillon et al 2003;Fitzgerald et al 2007;He et al 2010). Since the study on SRM pure-culture strains Desulfovibrio deseulfuricans first demonstrating its capacity for Hg methylation (Choi et al 1994), many studies linking Hg methylation to SRM species were conducted in natural habitats (Compeau and Bartha 1985;King et al 2000;Benoit et at.…”