how widespread are rhizosphere bacteria

Rhizosphere bacteria are ubiquitous across all terrestrial ecosystems. They vary in abundance and composition based on plant species, soil properties, and climate. In most soils, they make up a large fraction of microbial biomass. Dominant taxa include Pseudomonas, Bacillus, Rhizobium, and Streptomyces. Some exhibit global distribution while others are highly host-specific. Their functions are essential for nutrient cycling and plant health.