-Acyl Homoserine Lactone Production by the Marine Isolate, .

(isolate SD1D, with 98.5% sequence similarity to DMS 21967 KOPRI 20902) is a marine bacterium that was isolated from ballast tank fluids as part of a biofilm study in 2014. Our previous work indicated that although this strain produced no detectable biofilm, it was the only isolate to produce -acyl homoserine lactones (AHLs) in assays using the broad-range reporter strain, KYC55. The goal of the current study was to determine the types of AHL molecules produced by the isolate using gas chromatography-mass spectroscopy (GCMS) and C4- to C14-AHL as standards. A time course assay indicated that the strain produced the highest level of AHLs at 20 h of growth. When extracts were subjected to GCMS, detectable levels of C8- and C10-AHL and higher levels of C12-AHL were observed. Interestingly, several biofilm-forming isolates obtained from the same source also produced detectable amounts of several AHLs. Of the isolates tested, a strain designated SD5, with 99.83% sequence similarity to BCRC 17571, produced unstable biofilms, yet detectable levels of C6-, C8-, C10- and C12-AHL, and isolate SD8, an strain (98.85% sequence similarity), produced robust and stable biofilms accompanied by detectable levels of C8- and C12-AHL. All isolates tested produced C12-AHL at higher levels than the other AHLs. Results from this study suggest that quorum sensing and biofilm formation are uncoupled in . Whether the suite of AHLs produced by this isolate could modulate biofilm formation in other strains requires further study.