Insights into the diversity of grassland soil bacterial communities associated with four contrasting Köppen climatic zones of India

Abstract

AIMS : This study investigates the community structure and diversity of terrestrial soil bacterial communities thriving in four contrasting Köppen climatic zones of India using high-throughput sequencing. METHODOLOGY AND RESULTS : Soil samples were collected for metagenomic DNA isolation and PCR amplification using primers targeting the 16S rRNA gene region. Amplicons were subjected to Oxford nanopore sequencing and data analysis. Bacterial species diversity, evenness and richness were highest in a humid sub-tropical climatic zone (HSCZ). Firmicutes were the most abundant phylum in the tropical wet climatic zone (TWCZ), arid climatic zone (ACZ) and humid sub-tropical climatic zone (HSCZ), while Proteobacteria in the mountain climatic zone (MCZ). The predominance of class Alphaproteobacteria, Actinobacteria with genera Bradyrhizobium, Chthoniobacter and Mycobacterium, was observed in MCZ in contrast to class Bacilli with genera Bacillus and Paenibacillus in the rest of the zones. OTU abundance was positively correlated with moisture, TOC (total organic carbon), K, MAP (mean annual precipitation) and negatively correlated with pH, Ca, N, B, Fe, P, Mg and MAT (mean annual temperature). A significant correlation was only observed with Fe against Shannon diversity (H’) in multiple regression analysis. CONCLUSION, SIGNIFICANCE AND IMPACT OF STUDY : The multidirectional relationship between soil, its microbiota and climate is crucial in modulating bacterial community diversity and its survival in terrestrial ecosystems that significantly contribute to ecosystem function. This work mapped the occurrence and distribution of terrestrial soil bacterial communities in contrasting climatic zones for the first time, enabling us to assess the effect of climate in the mentioned Köppen climatic zones.