RETENTION OF THE GRAM-NEGATIVE MARINE BACTERIUM SW8 ON SURFACES - EFFECTS OF MICROBIAL PHYSIOLOGY, SUBSTRATUM NATURE AND CONDITIONING FILMS

The effect of films of organic compounds, the conditioning films (CF), adsorbed to the inanimate substrata stainless steel, germanium, polypropylene and perspex on retention of either the carbon (acetate)- or nitrogen (ammonia)-limited nonmotile Gram-negative marine bacterium SW8 was investigated. CF were deposited from marine or freshwater aquatic samples and from solutions containing bovine serum albumin, myoglobin, lactoglobulin or humic acids. SW8 was exposed to both ''clean'' and CF-coated test substrata in laminar fluid flow chambers for 10 min. CF modified attachment of SW8 relative to clean substrata in 70% of the cases. The following categories of CF were observed: (i) CF that appeared to control retention of SW8 irrespective of the type of substratum; (ii) CF that either increased or decreased the retention of SW8 on all substrata without altering the relative order of retention on the substrata and (iii) CF that affected retention of SW8 in an apparently substratum-specific manner. When retention of the two phenotypes differed, carbon-limited SW8 attached in higher numbers than nitrogen-limited SW8. No correlation was found between water contact angles on either ''clean'' or CF-coated substrata and retention of cells. In some experiments, SW8 was retained in aggregates. Such aggregation predominated on hydrophobic substrata, with nitrogen-limited organisms and on materials coated with CF from environmental waters. No difference in hydrophobicity or surface charge was found between the two physiologically different states of the organism. The ecological implications of these results and possible mechanisms of interactions of organisms with CF-coated substrata are discussed.