Biochar mediated differential regulation of oxidative stress and energy supply in Bacillus subtilis and Rhizoctonia solani

Abstract

Biochar (BC) significantly influences microbial metabolism, but its contrasting effects on different microorganisms remain unclear. This research explores the distinct regulatory mechanisms of BC on B. subtilis and R. solani. BC, consisting of micro-BC and nano-BC, generates reactive oxygen species (ROS), causing oxidative stress. Nano-BC can penetrate cells, leading to damage. In B. subtilis, BC initially inhibits growth, triggering endospore formation to expel nano-BC. B. subtilis secreted extracellular polymeric substances (EPS), which aggregated nano-BC, enhanced cell adhesion, and reduced intracellular ROS (from 2.0 to 1.5-fold), promoting growth later with BC’s nutrient support. Conversely, R. solani cannot block nano-BC entry, activating mitophagy and suppressing genes like ATP1,2 involved in oxidative phosphorylation and tricarboxylic acid cycle. This results in ATP deficiency, collapses antioxidant system, raises ROS (from 3.9 to 4.5-fold), decreases cell survival, and leads to cell death. These findings highlight BC’s selective microbial regulation and its potential for safe agricultural and environmental use.