INVESTIGATION OF N-ACYL HOMOSERINE LACTONE-BASED QUORUM-SENSING SYSTEM AND ALIGINATE LYASE ACTIVITY IN MARINE BACTERIAL SPECIES OF GRIMONTIA MARINA AS01 AND ALTEROMONAS MACLEODII AS02

Abstract

Production, detection, and reaction to external signaling molecules are essential steps in quorum sensing (QS) process. Through the use of QS, bacterial communities may synchronize their responses to shifts in the density and diversity of their vicinal neighbors. QS also play an important role in regulating enzmyatic activities among marine bacteria. The aim of the present study was to detect and identify N- acyl homoserine lactones (AHLs) based QS signaling molecules and the possible influence on alginate lyase in marine bacterial isolates of Grimontia marina AS01 and Alteromonas macleodi AS02. Marine water samples were collected from Arabian Sea, Karchi Pakistan, following the standard collection methods. Bacterial strains were isolated and pure cultured using Zobell 2216 marine medium. Molecular identification was achieved based on 16S rRNA gene analysis. Screening for AHLs was achieved using Agrobacterium tumefaciens A136 as a biosensor. Based on 16S rRNA analysis, the bacterial strains were identified as Grimontia marina strain AS01 (OP143768) and Alteromonas macleodii strain AS02 (OP143769). Cross-feeding bioassay revealed the positive reactions for the production of AHLs. Reversed phase-TLC analysis showed the identification of C6-HSL produced by G. marina AS01 and 3OXO-C6-HSL by A. macleodii AS02 strain. Moreover, QS inhibitor AiiA protein reduced the production of alginate lyase in A. macleodi AS02, while no effect was observed in G. marina AS01. These results substantiate the involvement of QS system in regulating alginate lyase activity in A. macleodii AS02. QS in marine bacteria may involve in hydrolysis of complex organic matter in marine environment.