Interactions of aquatic bacteria and aquatic nematodes were investigated to determine number and kinds of bacteria found in aquatic nematodes throughout Alabama, the effect of various bacterial metabolites on certain aquatic nematodes, and effect of various nematode products on growth of bacteria isolated from them. A total of 1842 potential bacterial-feeding nematodes from bottom and samples were surfaced, cleansed, crushed, and the residue cultured for associative bacteria of 15 genera. In determining suitability of bacteria as sole nutrient, nematodes showed growth and reproduction in a wide range of bacterial cell concentrations. Assay nematodes responded differently when fed the same species of bacteria suggesting differences in bacteria suitability as nematode nutrient. Certain bacteria produce nematocidal metabolites which could serve as biological control agents of certain nematodes. Chromobacterium produced two volatile toxic substances--cyanide and ammonia. Increased temperature where bacterial cells and nematodes are growing may cause, otherwise nutritious bacteria, to become toxic. (Author)