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We investigated changes in biomass, biochemical fingerprints, fatty acid methyl ester (FAME) profile and functional status of the natural aquatic microbial communities upon impact of an Atradex pulse. The Atradex was applied to microcosm tanks at concentrations ranging from 24.5microgL(-1) to 245mgL(-1). The biomass of all microbial communities declined to a minimum level on day 4 with the effect being more pronounced in treated groups. Similarity between microbial communities also decreased on day 4 with the greatest change occurring at a concentration of 245mgL(-1) Atradex. After 8 days exposure to Atradex, microbial communities in all treated groups (except tanks spiked with 245mgL(-1) Atradex) recovered and showed similar metabolic fingerprints and FAME profiles to those of controls. Our results indicate that exposure to an Atradex pulse at concentration above 245mgL(-1), may irreversibly change the structure and functional status of aquatic microbial communities.

A novel Escherichia coli outer membrane protein A (OmpA) was discovered through a proteomic investigation of cell surface proteins. DNA polymorphisms were localized to regions encoding the protein's surface-exposed loops which are known phage receptor sites. Bacteriophage sensitivity testing indicated an association between bacteriophage resistance and isolates having the novel ompA allele.

Escherichia coli has long been used as an indicator organism for water quality assessment. Recently there has been an accumulation of evidence that suggests some strains of this organism are able to proliferate in the environment, a characteristic that would detract from its utility as an indicator of faecal pollution. Phenotypic and genotypic characterization of E. coli isolated from blooms in two Australian lakes, separated by a distance of approximately 200 km, identified that the blooms were dominated by three E. coli strains. A major phenotypic similarity among the three bloom strains was the presence of a group 1 capsule. Genetic characterization of a conserved region of the cps gene cluster, which encodes group 1 capsules, identified a high degree of genetic variation within the bloom isolates. This differs from previously described encapsulated E. coli strains which are highly conserved at the cps locus. The phenotypic or genotypic profiles of the bloom strains were not identified in 435 E. coli strains isolated from vertebrates. The occurrence of these encapsulated strains suggests that some E. coli have evolved a free-living lifestyle and do not require a host in order to proliferate. The presence of the same three strains in bloom events in different geographical regions of a temperate climate, and at different times, indicates that free-living E. coli strains are able to persist in these water reservoirs. This study provides further evidence of circumstances where caution is required in using E. coli as an indicator organism for water quality.