# Bacillus velezensis S141: A Soybean Growth-Promoting Rhizosphere Bacterium

## TL;DR

This paper reviews the role of soybean root exudates in shaping rhizosphere microbial interactions, focusing on the plant growth-promoting bacterium Bacillus velezensis S141 and its potential for sustainable agriculture.

## Contribution

The paper introduces Bacillus velezensis S141 as a novel PGPR with unique traits like isoflavone hydrolysis and drought resilience, enhancing soybean growth and nitrogen fixation.

## Key findings

- Bacillus velezensis S141 promotes soybean growth through β-glucosidase activity and phytohormone production.
- Coinoculation with Bradyrhizobium spp. improves nodulation and nitrogen fixation in soybean.
- Comparative genomics reveal host-adaptive features of S141 distinct from other Bacillus strains.

## Abstract

Soybean (Glycine max) is a globally important crop, as it has high protein and lipid content and plays a central role in sustainable agriculture. Recent advances in rhizosphere biology have highlighted the critical role of soybean root exudates, particularly isoflavones and other secondary metabolites, in shaping microbial community structure and function. These exudates mediate complex, bidirectional signalling with rhizosphere microorganisms, influencing nutrient acquisition, stress resilience, and disease suppression. This review describes current knowledge on soybean–microbe interactions, with a focus on the emerging concept of the rhizosphere as a dynamic communication network. Particular attention is given to Bacillus velezensis S141, a plant growth-promoting rhizobacterium (PGPR) with distinctive traits, including β-glucosidase-mediated isoflavone hydrolysis, phytohormone production, and drought resilience. Coinoculation studies with Bradyrhizobium spp. demonstrate enhanced nodulation, nitrogen fixation, and yield, supported by transcriptomic and ultrastructural evidence. Comparative genomic analyses further underscore host-adaptive features of S141, distinguishing it from other Bacillus strains. Despite promising findings, mechanistic gaps remain regarding metabolite-mediated signalling and environmental robustness. Future research integrating metabolomics, synthetic ecology, and microbial consortia design will be essential to harness rhizosphere signalling for climate-resilient, low-input soybean cultivation.