# High-quality PacBio draft genome sequences of 17 free-living Bradyrhizobium and four related Nitrobacteraceae strains isolated from arid soils in the Santa Catalina Mountains of Southern Arizona

## TL;DR

Researchers sequenced genomes of 17 free-living Bradyrhizobium and four related bacteria from arid soils in Arizona, revealing insights into their genetic makeup and ecological roles.

## Contribution

The study provides high-quality draft genomes of non-symbiotic Bradyrhizobium and related Nitrobacteraceae strains from arid soils.

## Key findings

- The genomes range from 5.99 to 10.4 Mbp and cluster into four phylogenomic clades.
- The isolates lack genes for nitrogen fixation and nodulation, confirming their free-living, non-symbiotic nature.
- Two clades are within Bradyrhizobium, while two are basal to the genus within Nitrobacteraceae.

## Abstract

Non-symbiotic Bradyrhizobium are among the most abundant and ubiquitous microbes in bulk soils globally. Despite this, most available genomic resources for Bradyrhizobium are derived from plant-associated strains. We present high-quality draft genomes for 17 Bradyrhizobium and four Nitrobacteraceae cultures isolated from bulk semiarid soils in Arizona, USA. The genome sizes range from 5.99 to 10.4 Mbp. Phylogenomic analysis of the 21 genomes indicates they fall into four clades. Two of the clades are nested within the Bradyrhizobium genus. The other two clades were associated with Nitrobacteraceae outgroups basal to Bradyrhizobium. All genomes lack genes coding for molybdenum or vanadium nitrogenases, and nod genes that code for proteins involved in nodulation, suggesting these isolates are free-living, non-symbiotic and do not fix dinitrogen gas. These genomes offer new resources for investigating free-living Bradyrhizobium lineages.