title: Presence of quorum-sensing inhibitor-like compounds from bacteria isolated from the brown alga Colpomenia sinuosa.
abstract: OBJECTIVE
  Several Gram-negative bacterial species use N-acyl homoserine lactone (AHL) molecules as quorum-sensing (QS) signals to regulate various biological functions. Similarly, various bacteria can stimulate, inhibit or inactivate QS signals in other bacteria by producing molecules called as quorum-sensing inhibitors (QSI). Our aim was to screen and identify the epibiotic bacteria associated with brown algae for their ability of producing QS-inhibiting activity.
  
  
  RESULTS
  QSI screenings were conducted on several epibiotic bacteria isolated from a marine brown alga Colpomenia sinuosa, using Serratia rubidaea JCM 14263 as an indicator organism. Strain JCM 14263 controls the production of red pigment, prodigiosin by AHL QS. Out of 96 bacteria, which were isolated from the surface of the brown alga, 12% of strains showed the ability to produce QSI, which was observed from the pigmentation inhibition on Ser. rubidaea JCM 14263 without affecting its growth. Phylogenetic analysis using 16S rRNA gene sequencing method demonstrated bacterial isolates showing QS inhibition-producing bacteria belonging to the Bacillaceae (Firmicutes), Pseudomonadaceae (Proteobacteria), Pseudoalteromonadaceae (Proteobacteria) and Vibrionaceae (Proteobacteria).
  
  
  CONCLUSIONS
  An appreciable percentage of bacteria isolated from the brown alga produced QSI-like compounds.
  
  
  CONCLUSIONS
  The screening method using Ser. rubidaea described in this report will facilitate the rapid identification of QSI-producing bacteria from marine environment. This study reveals new avenue for future environmental applications. This study also suggests that these algal epibiotic bacteria may play a role in the defensive mechanism for their host by producing QSI or QSI-like compounds to suppress the settlement of other competitive bacteria.
authors.affiliation: Environmental Biochemistry Group, Research Center for Inland Seas, Kobe University, Higashinada-ku, Kobe SK-82475, Japan. manmadhan_k@yahoo.co.uk
authors.forename: M
authors.initials: M
authors.lastname: Kanagasabhapathy
authors.forename: G
authors.initials: G
authors.lastname: Yamazaki
authors.forename: A
authors.initials: A
authors.lastname: Ishida
authors.forename: H
authors.initials: H
authors.lastname: Sasaki
authors.forename: S
authors.initials: S
authors.lastname: Nagata
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D001685:Biological Factors / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D000459:Phaeophyceae / Q000382:microbiology*; D010802:Phylogeny; D053038:Quorum Sensing / Q000187:drug effects*; D012705:Serratia / Q000187:drug effects / Q000502:physiology
chemical_list: D001685:Biological Factors