Insect pathogenicity in plant-beneficial pseudomonads: phylogenetic distribution and comparative genomics

Abstract

Bacteria of the genus Pseudomonas occupy diverse environments. The Pseudomonas fluorescens group is particularly well-known for its plant-beneficial properties including pathogen suppression. Recent observations that some strains of this group also cause lethal infections in insect larvae, however, point to a more versatile ecology of these bacteria. We show that 26 P. fluorescens group strains, isolated from three continents and covering three phylogenetically distinct sub-clades, exhibited different activities toward lepidopteran larvae, ranging from lethal to avirulent. All strains of sub-clade 1, which includes Pseudomonas chlororaphis and Pseudomonas protegens, were highly insecticidal regardless of their origin (animals, plants). Comparative genomics revealed that strains in this sub-clade possess specific traits allowing a switch between plant-and insect-associated lifestyles. We identified 90 genes unique to all highly insecticidal strains (sub-clade 1) and 117 genes common to all strains of sub-clade 1 and present in some moderately insecticidal strains of sub-clade 3. Mutational analysis of selected genes revealed the importance of chitinase C and phospholipase C in insect pathogenicity. The study provides insight into the genetic basis and phylogenetic distribution of traits defining insecticidal activity in plant-beneficial pseudomonads. Strains with potent dual activity against plant pathogens and herbivorous insects have great potential for use in integrated pest management for crops.

Diversity of phytobeneficial traits revealed by whole‐genome analysis of worldwide‐isolated phenazine‐producing Pseudomonas spp.

“…As for the fourth subgroup, the two strains CMR5c and CMR12a were isolated from the rhizosphere of cocoyam in Cameroon among other closely related isolates and were selected for their ability to supress cocoyam root rot disease (Perneel et al, ). These two strains have been successively affiliated to the Pseudomonas putida species complex (Mavrodi et al, ) and, more recently, to the Pseudomonas fluorescens species complex (Ruffner et al, ; Flury et al, ). Our finding confirms the later affiliation, as P. protegens is currently the closest described species to these two strains.…”

Relationships between Root Pathogen Resistance, Abundance and Expression of Pseudomonas Antimicrobial Genes, and Soil Properties in Representative Swiss Agricultural Soils

“…et al, 2012). An examination of genome sequences published by Flury et al (2016) and other investigators indicated that fluorescent pseudomonads harbor only one copy of phlD , phzF , or prnD per cell. Accordingly, we did not find any significant difference between the abundances of phlD and phzF quantified by qPCR or a cultivation-dependent endpoint dilution assay in samples from Taenikon (Supplementary Figure S4).…”

“…Since all in vivo standard curves were prepared with bacterial cells recovered from wheat roots, the CT values can be directly converted to numbers of bacteria harboring phlD , phzF , or prnD per g root. Our qPCR data also directly reflect the abundance of the antimicrobial biosynthesis genes because phlD, phzF , or prnD are present in single copy in genomes of the P. fluorescens group (Flury et al, 2016). A survey of published bacterial genomes revealed that phzF and prnD are also found as a single copy in other bacterial species such as Burkholderia ( phzF and prnD ), Pectobacterium ( phzF ) or Serratia ( prnD ).…”

“…The obtained fragment was digested with BamHI and EcoRI and ligated into the mcherry -based promoter-probe vector pME9010 (Rochat et al, 2010) opened with the same enzymes. Similarly, for the construction of the phzA-mcherry reporter plasmid pME11017, a 961-bp fragment containing the phzA promoter (Chin-A-Woeng et al, 2001) was amplified from genomic DNA of PCL1391 (Flury et al, 2016) using primers phzAF and phzAR ( Table 3 ). The PCR product was digested with BamHI-SacI and the resulting fragment was first cloned into pUK21 and, from there, into pME9010, both opened with the same restriction enzymes.…”

Role of phenazines and cyclic lipopeptides produced by pseudomonas sp. CMR12a in induced systemic resistance on rice and bean

“…Pseudomonas sp. CMR12a is an uncharacterized new species that is taxonomically positioned between P. protegens and P. chlororaphis in the P. fluorescens group (Ruffner et al, 2015, Flury et al, 2016. Pseudomonas sp.…”