Identifying the suite of genes central to swimming in the biocontrol bacteriaPseudomonas protegensPf-5

Abstract

Swimming motility is a key bacterial trait, important to success in many niches, including assisting in colonization of host surfaces. Biocontrol bacteria, such asPseudomonas protegensPf-5 are increasingly being used as an agricultural tool to control crop diseases, where motility is a factor in successful colonization of the plant rhizosphere. Swimming motility has been studied in a range of bacteria and typically involves a suite of flagella and chemotaxis genes, however the specific gene set employed for both regulation and biogenesis can differ substantially between organisms. Here we used transposon directed insertion site sequencing (TraDIS), a genome-wide approach, to identify 249 genes involved inP. protegensPf-5 swimming motility. As expected, flagella and chemotaxis genes comprised a large proportion of these genes. However we also identified a suite of additional genes important for swimming, including genes related to peptidoglycan turnover, O-antigen biosynthesis, cell division, signal transduction, c-di-GMP turnover and phosphate transport, along with 27 conserved hypothetical proteins. Experimental gene knockout mutants and TraDIS data together suggest that defects in the Pst phosphate transporter lead to enhanced swimming motility. Overall, this study expands our knowledge of pseudomonad motility and highlights the utility of a TraDIS-based approach for systematically analyzing the functions of thousands of genes. This work sets a foundation for understanding how swimming motility may be related to the inconsistency in biocontrol bacteria effectiveness and reliability in the field.ImportanceBiocontrol bacteria, such asPseudomonas protegensPf-5 are increasingly being used as an agricultural tool to control crop diseases, and motility is a key factor in their successful colonization of plant surfaces. Here we use a high-throughput approach to identify the suite of genes important for swimming motility inP. protegensPf-5. These included flagella and chemotaxis genes, as well as a variety of cell surface, cell division and signalling genes. We also show that defects in the Pst phosphate transporter lead to enhanced swimming motility, a hitherto unreported link between phosphate transport and swimming motility. Understanding the genetic basis of swimming motility enhances our knowledge of key processes in biocontrol bacteria that are needed to ensure their competitive success. This will contribute to developing strategies to increase the utility of biocontrol bacteria in agricultural settings to prevent crop losses.

Spatial refuges and nutrient acquisition predict the outcome of evolutionary rescue in evolving microbial populations

“…The encoded protein, Aer, is a transmembrane aerotaxis receptor that allows organisms to sense oxygen gradients in their environment and alter their motility accordingly (Hong et al, 2004). Mutations in aer have been similarly shown to alter cell swarming and swimming motility, and biofilm formation (Nichols and Harwood, 2000;Ueda, Ogasawara and Horiuchi, 2020;Fabian et al, 2023), essential functions for colonising environments such as soils and host tissues. Swarming motility of evolved clones with PFLU_4551 mutations displayed increased levels of motility relative to wildtype clones, supporting the role of PFLU_4551 in motility.…”