. In this work the growth characteristics and metabolic activities of the methanotrophic-heterotrophic groundwater community (culture MM1) as well as of individual community members were studied. When growing in shake flasks, under various methane and oxygen tensions, culture MM1 revealed the capability of a stable association consisting of one obligate methanotroph with type II intracytoplasmic membranes as the dominant strain, and four or five heterotrophs of different morphological, physiological and metabolic characteristics. Coexistence of different populations and the stability of culture MM1 under various conditions suggested that complex relationships may exist between the community members. Most of these relationships seem to be beneficial for both the methanotroph and heterotrophs, making the community adaptable to a range of environmental conditions containing methane as the only carbon source. Furthermore, faster and more complete transformation of 2-[4-(sulphophenyl)]decane (2C 10 LAS) by the community than by any of the community members alone, illustrates the role and importance of methanotrophic-heterotrophic interactions in combined metabolic attack on complex linear alkylbenzenesulphonates molecules.

The relationships and interactions within a methanotrophic-heterotrophic groundwater community were studied in a closed system (shake culture) in the presence of methane as the primary carbon and energy source and with the addition of the pure linear alkylbenzenesulfonate (LAS) congener 2-[4-(sulfophenyl)]decan as a cometabolic substrate. When cultured under different conditions, this community was shown to be a stable association, consisting of one obligate type II methanotroph and four or five heterotrophs possessing different nutritional and physiological characteristics. The results of experiments examining growth kinetics and nutritional relationships suggested that a number of complex interactions existed in the community in which the methanotroph was the only member able to grow on methane and to cometabolically initiate LAS transformation. These growth and metabolic activities of the methanotroph ensured the supply of a carbon source and specific nutrients which sustained the growth of four or five heterotrophs. In addition to the obligatory nutritional relationships between the methanotroph and heterotrophs, other possible interactions resulted in the modification of basic growth parameters of individual populations and a concerted metabolic attack on the complex LAS molecule. Most of these relationships conferred beneficial effects on the interacting populations, making the community adaptable to various environmental conditions and more efficient in LAS transformation than any of the individual populations alone.