Investigations into determining if shellfish bacteria were capable of biotransforming PSTs focussed on several common molluscan species, including: blue mussels, oysters, razorfish, cockles and scallops. Bacteria associated with these shellfish were isolated on marine agar and characterised by Gram stain, colony morphology and carbon utilisation profiles (BiOLOG). Selected isolates from groups demonstrating 90% similarity were screened for their ability to metabolise a range of PSTs (GTX 1/4, GTX2/3, STX, NEO, C1 and B1) using a novel screening method with confirmation by HPLC. Results suggest that bacteria from different shellfish, show varying capacity to utilise and transform PST analogues. For example, isolate M12 (present in mussels) was able to utilise Gonyautoxins (GTX) 1/4 with the concomitant production of GTX 2/3, while strain Q05 (isolated from Queen scallops) apparently degraded GTX 1/4 without the appearance of other GTXs. These findings raise questions as to the possible role of bacteria resident in the shellfish food transport system. Some researchers have suggested that the microflora play a role in supplying nutritional requirements of the host, this study demonstrates that bacteria may also play a part in PST elimination in molluscan species.