LAUSR

Abstract ‘Los Negritos” is an extremophile geothermal site from Michoacan State, Mexico. Evidence of the diversity of its microbiota and its potential is still lacking. This study aimed to evaluate the bacterial communities by 16S metagenomics of the site and the potential of culturable bacteria isolated from the site by promoting growth plants (PGP) traits. Gemmatimonadetes phylum was the most abundant, followed by Actinobacteria, Alphaproteobacteria, and Firmicutes. A total of 15 culturable strains were isolated and identified. They belong to five different species: Bacillus seohaeanensis, Jeotgalibacillus alkaliphilus, Halobacillus andaensis, Thalassobacillus devorans, and Halobacillus campisalis. The phytohormone indole-3-acetic acid (IAA) production was in the interval from 14.78 to 46.52 mg L−1. The best IAA producers were T. devorans E18 and H. campisalis E20 with tryptophan and H. andaensis, T. devorans, and H. campisalis without tryptophan ranging 39.8 to 51.5 mg L−1. Phosphorous solubilization capability was detected in J. alkaliphilus and T. devorans, whereas B. seohaeanensis was the highest ammonium producer (34.1 ± 0.52 mg L−1) and H. andaensis was positive for siderophore production. These results demonstrate that, despite the low diversity, bacteria isolated from ‘Los Negritos’ have the potential for plant growth promotion.