title: Endophytic actinomycetes: a novel source of potential acyl homoserine lactone degrading enzymes.
abstract: Several Gram-negative pathogenic bacteria employ N-acyl-L-homoserine lactone (HSL) quorum sensing (QS) system to control their virulence traits. Degradation of acyl-HSL signal molecules by quorum quenching enzyme (QQE) results in a loss of pathogenicity in QS-dependent organisms. The QQE activity of actinomycetes in rhizospheric soil and inside plant tissue was explored in order to obtain novel strains with high HSL-degrading activity. Among 344 rhizospheric and 132 endophytic isolates, 127 (36.9%) and 68 (51.5%) of them, respectively, possessed the QQE activity. The highest HSL-degrading activity was at 151.30 ± 3.1 nmole/h/mL from an endophytic actinomycetes isolate, LPC029. The isolate was identified as Streptomyces based on 16S  rRNA gene sequence similarity. The QQE from LPC029 revealed HSL-acylase activity that was able to cleave an amide bond of acyl-side chain in HSL substrate as determined by HPLC. LPC029 HSL-acylase showed broad substrate specificity from C6- to C12-HSL in which C10HSL is the most favorable substrate for this enzyme. In an in vitro pathogenicity assay, the partially purified HSL-acylase efficiently suppressed soft rot of potato caused by Pectobacterium carotovorum ssp. carotovorum as demonstrated. To our knowledge, this is the first report of HSL-acylase activity derived from an endophytic Streptomyces.
authors.affiliation: Department of Biology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.
authors.forename: Surang
authors.initials: S
authors.lastname: Chankhamhaengdecha
authors.forename: Suphatra
authors.initials: S
authors.lastname: Hongvijit
authors.forename: Akkaraphol
authors.initials: A
authors.lastname: Srichaisupakit
authors.forename: Pattra
authors.initials: P
authors.lastname: Charnchai
authors.forename: Watanalai
authors.initials: W
authors.lastname: Panbangred
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism*; D000581:Amidohydrolases / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D016973:Pectobacterium carotovorum / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology*; D012331:RNA, Fungal / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D058441:Rhizosphere; D012988:Soil Microbiology; D011198:Solanum tuberosum / Q000382:microbiology*; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D054742:Acyl-Butyrolactones; D005656:Fungal Proteins; D012331:RNA, Fungal; D012336:RNA, Ribosomal, 16S; D000581:Amidohydrolases