UC Irvine

Increases in frequency and intensity of freshwater cyanobacterial blooms (cyanoHABs) place significant challenges to drinking water plants for human health protection from exposure to algal toxins. Specifically, microcystins (MC), the hepatotoxin produced by cyanobacteria, is not effectively removed by the current water treatment processes. The goal of this study is to isolate and characterize bacteria that are capable of degrading MC in order to develop biofilters that can effectively remove the toxin. Water and sediment samples from a drinking water reservoir and a freshwater pond were collected and enriched for MC degrading bacteria. Among nearly 100 fast growing bacterial isolates were obtained from the enrichment culture and identified by gene sequencing, none were MC degraders due to the carryover of the trace amount of ethanol in the MC stock that were used by fast growing non-degraders. On the contrary, the bacterial consortia obtained from enrichment cultures can efficiently degrade MC. Although both consortia enriched in the presence or absence of ethanol can perform MC degradation, the degradation rates were improved for most of the consortia when the ethanol was removed from the enrichment culture in spite of lower cell growth rate. This indicates that the fast growing bacteria in the enrichment culture are not the key players in the degradation of MC. Bacterial community analysis also confirmed the higher diversity in consortia associated with ethanol. However, there is not a clear separation of bacterial diversity between the MC degrading and non-degrading consortia, indicating the complexity of consortia in MC degradation.