Clearance of Escherichia coli by the freshwater mussel Lamellidens marginalis in laboratory conditions

Scientists and environmentalists are searching for biological remedies to reduce E. coli concentrations in waterbodies to acceptable levels. The present research was conducted to investigate clearance of E. coli isolated from freshwater mussels (Lamellidens marginalis) in the Old Brahmaputra River, Mymensingh, Bangladesh by conspecific mussels from the same river in aquarium conditions. Mussels were acclimated, depurated and divided into three shell length (SL) groups. Small (38.28 +/- 2.81 mm), medium (47.28 +/- 1.52 mm) and large (55.89 +/- 2.25 mm) mussels were assigned to aquaria designated as T-2, T-3 and T-4 respectively whereas empty mussel shells were assigned to T-1 as control in triplicate. After addition of pure E. coli suspensions, 3 mL water samples from each aquarium were collected at hourly intervals for 12 h for total E. coli count (TEC). Statistical analysis revealed that both time and treatments have significant effects (P < 0.05) on TEC. Presence of live mussels caused 1.41-1.63 log(10) reduction of TEC after 12 h compared to the control. However, such differences were not consistent among the different SL groups. In conclusion, L. marginalis is capable of reducing E. coli concentrations although the efficacy is not consistently related with mussels' shell lengths.