The Microbiological Aspects of Early Stages of Marine Fouling

Abstract

In this study, the ecology of attached marine bacterial populations on materials of economic significance was considered. Specific aspects of the microbial film examined were its composition, construction, and dynamics of bacterial attachment. Precise and practical methods for collecting data from the natural environment were developed; the construction of a novel sample holder was described together with a procedure for the isolation of attached bacteria from surfaces and the selection of an efficient ‘non-selective’ heterotrophic growth medium. Techniques for the enumeration of bacteria on surfaces were assessed and the use of an acridine orange staining method with UV-epiflourescence microscopy described. Various substrates representing a range of surface energy values (wettability) were immersed in seawater for different lengths of time during summer and winter seasons. Bacterial densities and rates of attachment were found to be greater during the summer than the winter due to, and concomitant with, seasonal levels of bacterial number in seawater. The substrate characteristic wettability influenced dynamics during the first twelve hours of substrate immersion such that, with decreasing wettability, there was an increase in attachment density and rate. It is suggested that microbial attachment may be effected by one of three processes: polymeric fibril synthesis, flagella cell/surface binding, and chemisorption. It is considered that the majority of adhesion events occur by chemisorption. The microbial film was composed mainly of gram negative rods, predominantly from the genera Pseudomonas and Alteromonas, and to a lesser extent, by gram positive coryneforms. Composition was affected by the substrate; communities were found to consist largely of substrate non-specific and, to a lesser extent, substrate specific types. Microbial film development, the product of an interaction between attached, attaching cells, and the surface, was found to be a population characteristic, independent of substrate and environmental factors. FOULING : MICROBIAL FILMS : ATTACHMENT : SURFACES