PSYCHROPHILIC ECOSYSTEMS OF INTEREST FOR WASTE-WATER TREATMENT - MICROBIOLOGIC AND IMMUNOLOGICAL ELUCIDATION OF THEIR METHANOGENIC FLORA

A model study was designed to identify natural ecosystems in a defined geographical area (Catalonia, Spain) that could be used as a source of inocula for digesters in wastewater-treatment plants serving that area. After a preliminary survey of a variety of places, three ecosystems were targeted for further analysis. These were freshwater, marine and lake sediments from the Besos river, the mouth of the Llobregrat river, and the Banyoles lake, respectively. The specific aim of the work reported here was to examine the methanogenic flora of the sediments. Immunologic assays and antigenic fingerprinting with a panel of calibrated antibody probes were used in parallel with standard microbiologic and DNA-DNA hybridization methods to identify and quantify methanogenic bacteria. Methanosarcina, Methanothrix, Methanobacterium, Methanobrevibacter, and Methanogenium species were found, some antigenically closely related, if not identical, to reference organisms while other isolates represent as yet undescribed immunotypes. The sediment from the Besos river contained the largest variety of species in the highest concentration; because of this and of its easy accessibility, this freshwater sediment was chosen for testing its potential for starting up anaerobic digesters under conditions pertinent to the needs of the region surveyed.