Isolation and Characterization of Microorganisms from Edible Bivalves as Potential Agents for Bioremediation

Bivalves are common marine species which are used as bio-indicators. These organisms are filter feeders and have a tendency to accumulate heavy metals and organic pollutants from sea water in their tissue. Their gills host microorganisms, which are also exposed to the heavy metals and other pollutants.The objective of the present study was to isolate and characterize these microorganisms and explore their potential for bioremediation of polluted waters. Eight different microbial cultures were isolated from edible clams (bivalve molluscs) collected from the coast of Mumbai and Alibaug. Biochemical and morphological tests were performed to characterize the isolated bacteria. All the eight cultures showed growth in 8% NaCl solution indicating that they are halotolerant. Gradient plate method was used to test resistance of the isolates to three dyes commonly used for painting of idols – Fluoorange, Fluo green and Fluo blue and Malachite green. The isolates were also tested for metal resistance against Zn, Cu, Co and Pb using agar cup method. It was observed that six isolates (AS1, AS3, MS3, MS4, MS9, MS11) were resistant to the three selected dyes while two isolates (AS2, MS1) were sensitive. AS1, AS3, MS9 and MS11 were found to be resistant to Malachite green up to 0.01 mg/ml. MS11, identified as Staphylococcus arlettae, showed the highest tolerance to metals – up to 80 mM of ZnSO₄, CuSO₄, CoCl₂ and PbNO₃. For the other isolates the resistance to metals was variable; MS4 was found to be most sensitive. The results suggest that the isolated bacteria, Staphylococcus arlettae, from bivalves has resistance to toxic chemicals and may find application in bioremediation processes.