Aer Receptors Influence thePseudomonas chlororaphisPCL1606 Lifestyle

Pseudomonas chlororaphisPCL1606 (PcPCL1606) is a rhizobacterium isolated from avocado roots, which is a favorable niche for its development. This strain extensively interacts with plant roots and surrounding microbes and is considered a biocontrol rhizobacterium. Genome sequencing has shown the presence of thirty-one potential methyl-accepting chemotaxis proteins (MCPs). Among these MCPs, two candidates are putative functional aerotaxis receptors, encoded at locus PCL1606_41090 (aer1-1) and locus PLC1606_20530 (aer1-2), that are homologous to the Aer receptor ofPseudomonas aeruginosastrain PaO1. Single- and double-deletion mutants in one or both genes have led to motility deficiencies in oxygen-rich areas, particularly reduced swimming motility compared with that of wildtype PcPCL1606. No differences in swarming tests were detected, and less adhesion by theaerdouble mutant was observed. However, the single and double mutants on avocado plant roots showed delayed biocontrol ability. During the first days of the biocontrol experiment, theaer-defective mutants also showed delayed root colonization. The current research characterizes the presence ofaertransductors onP. chlororaphis. Thus, the functions of the PCL1606_41090 and PCL1606_20530 loci, corresponding to genesaer1-1 andaer1-2, respectively, are elucidated.