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

Abstract

Background 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. 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. Results While 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. Conclusions This 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.

Organic and Inorganic Amendments Shape Bacterial Indicator Communities That Can, In Turn, Promote Rice Yield

“…Mushroom residues contain poly-aromatic hydrocarbons (a kind of organic matter derived from mushroom residues) and are considered xenobiotic compounds [51], or in other words, a substrate that can specifically select for Actinobacteria to degrade and convert to nutrients for the rice plant to uptake. This observation is in line with previous studies indicating that Actinobacteria play a key ecophysiological role in plant residue decomposition [52,53].…”

Soil metabolomics and bacterial functional traits revealed the responses of rhizosphere soil bacterial community to long-term continuous cropping of Tibetan barley

“…After 10 years of continuous cropping of Tibetan barley, Actinobacteria and Proteobacteria were the two main dominant phyla that were enriched in many rhizosphere soils after continuous cropping, such as in sugarcane and cotton ( Pang et al, 2021 ; Xi et al, 2019 ). The widely distributed bacterial phyla, Actinobacteria, possess high proportions of CAZymes and exhibited a key important eco-physiological role in plant residue decomposition in a previous study ( Bao et al, 2021 ). Another abundant phylum, Proteobacteria, plays a central role in the cycling of several key elements, including N- ( Conthe et al, 2018 ), C- ( Chan et al, 2013 ), and S-cycling ( Zhou et al, 2020 ).…”

Comparison of soil microbial community and physicochemical properties between rice–fallow and rice–bean (green manure) rotation

“…The higher Actinobacteria abundance in RF was probably caused by its character to prefer less fertile soils (Y. Bao et al, 2021). The bacterial taxonomic groups at the genus level showed more responses to the treatments.…”