Important ecophysiological roles of non-dominant Actinobacteria in plant residue decomposition, especially in less fertile soils

Yuanyuan Bao,Xiangui Lin,Jan Dolfing,Zhongpei Li,Ruirui Chen,Youzhi Feng,Zhiying Guo,Meng Wu

doi:10.1186/s40168-021-01032-x

Abstract

BackgroundMicrobial-driven decomposition of plant residues is integral to carbon sequestration in terrestrial ecosystems. Actinobacteria, one of the most widely distributed bacterial phyla in soils, are known for their ability to degrade plant residues in vitro. However, their in situ importance and specific activity across contrasting ecological environments are not known. Here, we conducted three field experiments with buried straw in combination with microcosm experiments with 13C-straw in paddy soils under different soil fertility levels to reveal the ecophysiological roles of Actinobacteria in plant residue decomposition.ResultsWhile accounting for only 4.6% of the total bacterial abundance, the Actinobacteria encoded 16% of total abundance of carbohydrate-active enzymes (CAZymes). The taxonomic and functional compositions of the Actinobacteria were, surprisingly, relatively stable during straw decomposition. Slopes of linear regression models between straw chemical composition and Actinobacterial traits were flatter than those for other taxonomic groups at both local and regional scales due to holding genes encoding for full set of CAZymes, nitrogenases, and antibiotic synthetases. Ecological co-occurrence network and 13C-based metagenomic analyses both indicated that their importance for straw degradation increased in less fertile soils, as both links between Actinobacteria and other community members and relative abundances of their functional genes increased with decreasing soil fertility.ConclusionsThis study provided DNA-based evidence that non-dominant Actinobacteria plays a key ecophysiological role in plant residue decomposition as their members possess high proportions of CAZymes and as a group maintain a relatively stable presence during plant residue decomposition both in terms of taxonomic composition and functional roles. Their importance for decomposition was more pronounced in less fertile soils where their possession functional genes and interspecies interactions stood out more. Our work provides new ecophysiological angles for the understanding of the importance of Actinobacteria in global carbon cycling.3uWhKDWFjqsFeP9DMWUatJVideo abstract

Highlights

Microbial-driven decomposition of plant residues is integral to carbon sequestration in terrestrial ecosystems
Differences in the abundances of Actinobacteria and their functional genes between soils with different fertilities Further to the above analyses, we evaluated whether the functional genes in the metagenome can support our second hypothesis that Actinobacteria are more important in less fertile soils
Even though the carbohydrate-active enzymes (CAZymes) derived from Actinobacteria were 14.5% and 17.5% of the total CAZymes for CS and YT, respectively (Fig. 5a), the average relative abundances of Actinobacteria only accounted for 2.5% and 6.6% of the all classes of CAZymes were found in other phyla, the high functional variability in these phyla in our study suggests that the reason behind it may differ from that of Actinobacteria

Summary

Introduction

Microbial-driven decomposition of plant residues is integral to carbon sequestration in terrestrial ecosystems. Actinobacteria, one of the most widely distributed bacterial phyla in soils, are known for their ability to degrade plant residues in vitro. Their in situ importance and specific activity across contrasting ecological environments are not known. Actinobacteria, one of the most widely distributed phyla among soil bacteria [17], are well known for their ability to degrade plant residues [17,18,19]. Ecological and physiological aspects both suggest a broad adaptation of Actinobacteria communities to degrade plant residues and potential importance of Actinobacteria to residue decomposition and soil carbon sequestration. We hypothesize that Actinobacteria play important ecophysiological roles in plant residue decomposition and are prevalent in environments where this process occurs

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