Pseudomonas chlororaphis PCL1606 (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 of
Pseudomonas aeruginosa strain 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 the aer double 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, the
aer-defective mutants also showed delayed root colonization. The current research
characterizes the presence of aer transductors on P. chlororaphis. Thus, the functions
of the PCL1606_41090 and PCL1606_20530 loci, corresponding to genes aer1-1 and
aer1-2, respectively, are elucidated.
