Institute of Ecosystem Studies

2008 BES Annual Meeting Presentation and Poster Abstracts

In–situ mortality rates and survival of Escherichia coli in agricultural and urban streams.
Higgins, James
Co-Authors: Higgins, James A. and Kenneth T. Belt
Abstract: We determined in-situ mortality rates of E. coli in fresh water streams in Baltimore and Beltsville, Maryland in different seasons. E. coli cultures with 107 to 108 organisms were put into 50,000 kDA dialysis tubes in the suburban upper Gwynns Falls (at Gwynnbrook) in five experiments (started in February, June, August, and November 2005) and in two experiments in the agricultural OP3E stream (in February 2007). Each experiment consisted of 5-6 tubes, which were retrieved at various time intervals E. coli isolates originating from the polluted Gwynns Run in Baltimore City and from chicken caecum were capable of surviving prolonged submergence in Gwynns Falls and OP3E streams despite being exposed to ambient temperatures, stormflows, sediment and water chemistries for lengthy periods. Despite high initial mortality rates, all five sets of experiments generated viable E. coli in both cold and warm weather, with total submergence times that ranged from 43 – 82 days. Mortality rates were lowest in the Fall and highest in the Winter, with intermediate values in the Summer. These data showed survival in excess of 80 days in warmer months of the year, and in excess of 50 days in colder months, periods similar to previously reported survival times in laboratory microcosms using K-12, and non-K-12, strains. E. coli survival experiments are typically done under highly controlled laboratory conditions. This work demonstrated long-term in-situ survival, and showed that the dialysis tube protocol offers a viable tool to study bacterial pathogen mortality.