Patterns, Processes, and Predictions: Soil bacteria unique habitats along a megametre transect in Eastern Australia

Abstract Bacteria distribution exhibited stronger regional preference even at high taxonomy. The increased land use intensity enhances the relative abundance of Actinobacteria and bacterial connectivity. Regionally unique bacterial taxa exhibit conserved adaptation to specific pedo-climatic thresholds, e. g. , CandidatusUdaeobacter for high precipitation, Rubrobacter for high pH. Soil microbiomes play a crucial role in ecosystem functioning, yet knowledge about region-specific bacterial taxa across diverse soil types, particularly at a continental scale, remains uncertain. This study employs 16S rRNA sequencing to analyze 141 soil samples collected along a 1 400 km transect in New South Wales, Australia, revealing distinct bacterial communities adapted to the varying climatic and soil conditions from east to west. The transect is characterised by three unique pedo-climatic zones: >900 mm mean annual precipitation in the eastern region, 900−300 mm in the central region, and <300 mm in the western region. These variations in climate and soil properties, particularly soil pH, organic carbon, and precipitation, significantly influence bacterial diversity and composition. We identified regionally enriched taxa, including Verrucomicrobia in the eastern, Chloroflexi in the central, and Gemmatimonadetes in the western, demonstrating the adaptation of microbial communities to local environmental conditions. Additionally, our findings show that increasing land use intensity, particularly in agricultural areas, correlates with higher Actinobacteria abundance and leads to more homogenised and interconnected microbial networks. This study provides new insights into the biogeography of soil bacteria in Australia, highlighting the importance of local environmental factors in shaping microbial community structure and offering valuable information for ecological and agricultural management strategies.