title: Characterization of bacteria degrading 3-hydroxy palmitic acid methyl ester (3OH-PAME), a quorum sensing molecule of Ralstonia solanacearum.
abstract: Bacterial wilt pathogen Ralstonia solanacearum causes severe crop loss of eggplant, which is of economic importance in India. 3-hydroxy palmitic acid methyl ester (3OH-PAME) is the main quorum sensing molecule governing the expression of virulence factors in R. solanacearum. Ability of 164 bacterial isolates from the xylem of eggplant (Solanum melongena L.), chilli pepper (Capsicum annuum L.) and wild eggplant (Solanum torvum Sw.) to degrade 3OH-PAME was tested by disc diffusion assay. Enzymatic degradation of 3OH-PAME by five bacteria was confirmed by High-Performance Liquid Chromatography-Mass Spectrometry analysis. 3OH-PAME degrading bacteria were identified as Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Rhodococcus corynebacterioides. 3OH-PAME degrading bacteria reduced the expression of virulence factors (exopolysaccharides and endoglucanase) of R. solanacearum in vitro and reduced wilt incidence in eggplant seedlings under greenhouse conditions. Isolates with quorum quenching activity successfully re-colonized eggplant seedlings. Quorum quenching bacteria produced antagonistic compounds, which may act synergistically with quorum quenching in reducing bacterial wilt in eggplant.
  
  
  CONCLUSIONS
  This is the first report on endophytic bacteria of class Gammaproteobacteria and phylum Actinobacteria having 3OH-PAME degrading activity. This study demonstrates the potential use of endophytic bacteria as quorum quenching biocontrol agents for management of bacterial wilt in eggplant.
authors.affiliation: ICAR Research Complex for Goa, Old Goa, Goa, India; Department of Microbiology, Goa University, Taleigao Plateau, Goa, India.
authors.forename: G A
authors.initials: GA
authors.lastname: Achari
authors.forename: R
authors.initials: R
authors.lastname: Ramesh
mesh_terms: D015373:Bacterial Typing Techniques; D002212:Capsicum; D007194:India; D010168:Palmitates / Q000737:chemistry / Q000378:metabolism*; D010169:Palmitic Acids / Q000737:chemistry / Q000378:metabolism*; D010627:Phenethylamines / Q000737:chemistry / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000378:metabolism; D053038:Quorum Sensing / Q000502:physiology*; D043368:Ralstonia solanacearum / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D012240:Rhodococcus / Q000378:metabolism; D032323:Solanum melongena / Q000382:microbiology; D020615:Stenotrophomonas maltophilia / Q000378:metabolism
chemical_list: D010168:Palmitates; D010169:Palmitic Acids; D010627:Phenethylamines; C108229:3-hydroxypalmitic acid; C037366:1-phenyl-1-aminomethylethene; C019012:methyl palmitate
keywords: 3OH-PAME; Ralstonia solanacearum; endophytic bacteria; quorum quenching; xylem