Microbial degradation of microcystin in Florida's freshwaters

Presence of microcystin (MC), a predominant freshwater algal toxin and a suspected liver carcinogen, in Florida's freshwaters poses serious health threat to humans and aquatic species. Being recalcitrant to conventional physical and chemical water treatment methods, biological methods of MC removal is widely researched. Water samples collected from five sites of Lake Okeechobee (LO) frequently exposed to toxic Microcystis blooms were used as inoculum for enrichment with microcystin LR (MC-LR) supplied as sole C and N source. After 20 days incubation, MC levels were analyzed using high performance liquid chromatography (HPLC). A bacterial consortium consisting of two isolates DC7 and DC8 from the Indian Prairie Canal sample showed over 74% toxin degradation at the end of day 20. Optimal temperature requirement for biodegradation was identified and phosphorus levels did not affect the MC biodegradation. Based on 16S rRNA sequence similarity the isolate DC8 was found to have a match with Microbacterium sp. and the DC7 isolate with Rhizobium gallicum (AY972457).