Physiological changes and rate of resistance of Acrosiphonia arcta (Dillwyn) Gain upon exposure to diesel fuel.

The changes in the morpho-physiological state of green alga Acrosiphonia arcta upon exposure to diesel fuel (DF) at concentrations of 20; 100; 1,000; 2,000; 3,000 of maximum permissible concentrations (MPC) were studied. The main physiological stress markers, such as enzymes of the antioxidant system (AOS), non-enzymatic antioxidants (carotenoids) and free amino acids (as components of plant metabolome) were measured. In general, all concentrations of the petroleum product used changed the activity of the antioxidant system, changed the intensity of physiological processes (photosynthesis, free amino acid synthesis) and also affected the structure of microbiomes inhabiting the surface of algae. It was shown that the concentration of DF within 1 mg/l (20 MPC) was not lethal as plants were able to maintain physiological activity and the observed changes were reversible. Although DF exposure caused decreases in superoxide dismutase (SOD) activity, proline concentration and photosynthetic rate, increases in catalase activity and pigment concentration were observed. After the effects of stress disappeared, most physiological parameters were restored, except for carotenoid content. Higher DF concentrations (100 MPC and higher) caused injury to cell structures and damage to the pigment apparatus. The restoration of functions after the termination of exposure to stress was not achieved. Epiphytic bacterial communities actively responded both to the introduction of a toxicant and to the changing physiological parameters of algae by the change in the numbers of cultured heterotrophic bacteria. The results of this study showed that the concentration of petroleum products in the water decreased to values not exceeding MPC in the presence of algae in the environment.

Epiphytic bacterial communities of the alga Fucus vesiculosus in oil-contaminated water areas of the Barents Sea.

Taxonomic compositions of epiphytic bacterial communities in water areas differing in levels of oil pollution were revealed. In total, 82 bacterial genera belonging to 16 classes and 11 phyla were detected. All detected representatives of epiphytic bacterial communities belonged to the phyla Actinobacteria, Bacteroidetes, Planctomycetes, Proteobacteria, Verrucomicrobia, Acidobacteria, Cyanobacteria, Firmicutes, and Fusobacteria and candidate division TM7. The ratio of the phyla in the communities varied depending on the levels of oil pollution. New data on taxonomic composition of uncultivated epiphytic bacterial communities of Fucus vesiculosus were obtained.

Aeromonas sobria, a causative agent of disease in farmed perch, Perca fluviatilis L.

Significant numbers of perch, Perca fluviatilis, raised on a pilot fish farm in Switzerland presented focal skin lesions on the lateral sides and fin rot. Mortality rates reached levels of up to 1% of the total fish on the farm per day. Virtually pure cultures of Aeromonas sobria were isolated from the liver, kidney, spleen and skin lesions of affected fish. Aeromonas sobria isolated from the farmed perch had a haemolytic effect on sheep and trout erythrocytes, autoaggregated, was cytotoxic for cultured fish cells and possessed genes involved in type III protein secretion. Experimental infection of naive perch with a single colony isolate of A. sobria from an affected farm fish resulted in the development of clinical signs identical to those seen on the farm. The results indicate that A. sobria can act as a primary pathogen of perch.