Identification of a Vibrio strain producing antimicrobial agents in the excretory organs of Nautilus pompilius (Cephalopoda: Nautiloidea)

摘要

The aim of the present study was to identify and characterize bacteria producing antimicrobial compounds in the excretory organs of iNautilus pompilius. Culture-dependent and culture-independent complementary approaches were used for bacterial identification such as: culture on selective media, Gram staining, CARD-FISH, direct DNA extraction from host tissue, PCR amplification and sequencing of the bacterial 16S rRNA gene. Results show presence of three bacterial groups: i^g-Proteobacteria with three clusters (iPseudomonadales, iVibrionales, iAlteromonadales), i^b-Proteobacteria and spirochetes. In order to screen for active strains, antimicrobial activity was tested by diffusion agar assay against iMicrococcus luteus, iEscherichia coli, iVibrio harveyi, and iCandida albicans. iNautilus isolates showed antimicrobial activities against both Gram-positive and Gram-negative reference strains. Most of the active strains were phylogenetically related to environmental iVibrionaceae. These strains were always abundant in iN. pompilius PA but were absent from iNautilus macromphalus from other geographical areas. Therefore, we suggest that antimicrobial active iVibrionaceae infect iN. pompilius by environmental transmission.