Comparative analysis of three Bradyrhizobium diazoefficiens genomes show specific mutations acquired during selection for a higher motility phenotype and adaption to laboratory conditions

ALTHABEGOITI MARÍA JULIA; LOZANO, MASURICIO; REDONDO-NIETO, MIGUEL; GARRIDO-SANZ, DANIEL; MONGIARDINI, ELÍAS; QUELAS, JUAN IGNACIO; MENGUCCI, FLORENCIA; DARDIS, CAROLINA; LODEIRO, ANIBAL

Microbiology Spectrum

Amer Soc Microbiology

Lugar: Washington, DC; Año: 2021

2165-0497

Microbial genomes are being extensively studied using Next-Generation Sequencing technologies in order to understand the changes that occur under different selection regimes. In this work, the number and type of mutations that have occurred in three related Bradyrhizobium diazoefficiens USDA 110T strains under laboratory conditions and during selection for a more motile phenotypic variant were analyzed. The first strain is the wild type from our laboratory (LP USDA 110), the second is a streptomycin resistant obtained from the wild type (LP 3004), and the third is a higher motility strain derivative from the latter (LP 3008). Most of the mutations found in both processes consisted of single nucleotide polymorphisms, single nucleotide deletions or insertions. In the case of adaptation to laboratory conditions, half of the changes occurred within intergenic regions and around 80 % were insertions. When the more motile phenotypic variant was evaluated, eight single nucleotide polymorphisms and an 11-bp deletion were found, although none of them was directly related to known motility or chemotaxis genes. Two mutants were constructed to evaluate the 11-bp deletion affecting the alpha subunit of 2-oxoacid acceptor oxidoreductase (AAV28_RS30705-blr6743). The results showed that this single deletion was not responsible for the enhanced motility phenotype.