Microbial modification of ground water

When ground water is tapped by wells, microbial and chemical deposits often develop. Sloughing and clogging may occur in the distribution system adding considerable expense to the operation of the water systems as well as imparting taste and odor to the water itself. The purpose of this project has been to define the physical and microbial basis of these deposits using microbial flocs found in Southern Illinois as a "model system." These flocs proliferate at the air-water interface of a domestic flush tank producing copious amounts of flocculent material. Observation of the flocs by phase microscopy revealed a dense population of bacteria with several distinct morphological types. Analysis by scanning and transmission electron microscopy revealed that the floc members reside in a matrix and that the consortium consists of two ultrastructurally distinct types of bacteria. Results of chemical analysis of the well water indicated low levels of organic material, whereas results of gas chromatographic analysis indicated high amounts of methane to be present in the water. The predominant organism, an elipsoidal rod, was isolated from floc enrichments grown under a methane-air atmosphere. Two organisms of a second morphological cell type have also been isolated and their unique nutritional properties investigated. Extracellular matrix produced by the two organisms appear to be responsible for the formation of the floc. A number of heterotrophic organisms have also been isolated from the consortium. Cross-feeding experiments involving mixed cultures of the consortium isolates revealed a microbial food chain to exist with methane as the primary energy source for the development of these aquatic consortia. Dissolved methane in ground waters is a previously unappreciated energy source for the development of microbial communities in water supplies.U.S. Department of the InteriorU.S. Geological Surve