A research team led by Prof. WANG Guanghua from the Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences (CAS) has uncovered how microbial adaptive evolution and regulatory strategies respond to soil carbon heterogeneity in paddy soils across spatial scales. 

Their findings were published in Geoderma on March 17.

Paddy soils, recognized as critical carbon sinks, can sequester 39% to 127% more soil organic carbon (SOC) than upland soils. Yet, the mechanisms by which microbial communities adapt and regulate carbon cycling in these complex environments have remained largely elusive.

According to the researchers, significant distance-decay relationships (DDRs) were observed at both microbial carbon functional and genomic taxonomic levels. Microbial cycling profiles carbon were clustered into two groups. HCS (including sites R1-R10) represented soils with high total carbon (TC) at relatively high latitudes, whereas LCS (including sites R11-R30) had low soil content distributed at low latitudes.carbon Compared with HCS, LCS presented higher abundances of cycling pathways involving aerobic respiration, Carbon fixation, and methanogenesis pathways, as well as higher levels of carbohydrate esterase (CE) and glycosyl transferase (GT) classes.

211 metagenome-assembled genomes (MAGs) with diverse carbon metabolic functions were constructed. Among these, high-quality MAG292, assigned to the Nanopelagicales order, had a significantly positive correlation with TC and was more abundant in HCS. Contrarily, MAG153, assigned to the Chitinophagales order, exhibited an opposite trend.

Additionally, 133 novel vMAGs were retrieved, and the abundances of phage11, phage16, phage26, and phage120 were higher in LCS than in HCS, containing chiA and GH19 that involved in chitin degradation. HCS had a relatively high abundance of phage89, containing slt and GH23 genes that regulate peptidoglycan lysis.

These results indicated that soil viruses potentially lyse bacteria by encoding peptidoglycan lyase, releasing nutrients, and increasing the amount of dead microbial debris that facilitates soil carbon accumulation at relatively high latitudes. In contrast, at low latitudes, the phages together with microbes may indirectly decrease the soil TC by potentially expressing auxiliary metabolic genes (AMGs) involved in chitin degradation.

It highlights the divergent microbial adaptive evolution and soil carbon regulation strategies response to soil carbon heterogeneity in paddy soils of Chinese Mollisols.

This study was supported by the National Key Research and Development Program of China and the Youth Innovation Promotion Association of CAS.

Schematic showing the adaptive and regulatory mechanisms of microbes and potentially associated viruses with soil carbon heterogeneity in paddy soils. (Image by HU Xiaojing)