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Background. The ability to biosynthesis of antibiotics was established for 20 of 250 species of Pseudomonas . The value of the biosynthesis of antibiotics as a taxonomic characteristic for the genus Pseudomonas is not studied. This issue will be analyzed using the experimental results. Оbjective. The aim of the paper is to identify the ability of usage of antibiotics synthesized by certain types of bacteria of the genus Pseudomonas , as a taxonomic marker. Methods. Methods of thin-layer chromatography (TLC) and LC/MS-analysis were used to determine the synthesis of antibiotics. Results. A unique set of antibiotics was determined for some types of bacteria Pseudomonas, which are specific for them only: pyocyanin – P. aeruginosa , 2,4-diacetylphloroglucinol – P. brassicacearum , 2-hydroxyphenazine-1-carbo­xylic acid – P. chlororaphis subsp. aureofaciens , pyrrolnitrin and 2,4-diacetylphloroglucinol – P. protegens , batumin – P. batumici . Conclusions. The ability to synthesize certain antibiotic substances may serve as a taxonomic marker and be used to identify certain species of Pseudomonas . However, the biosynthesis of antibiotics did not show specificity for several species. This problem requires a deeper study of different types of Pseudomonas .

The phenotypic, chemotaxonomic and genetic peculiarities of 5 deep strains of Alteromonas macleodii (isolated from Adriatic and Ionian Sea water from a depth of 1,000-3,500 m) and 5 strains of the same species isolated from the surface layer of Aegean, Andaman, Black Sea and Atlantic Ocean water near the British shore have been studied. Electron microscopy has shown that the deep strains' cells were, on average, two times longer (2.1±0.2×0.7±0.1 µm) than the surface strains' (1.1±0.1×0.6±0.1 µm). Using fatty acid analysis (particularly the mono-unsaturated C16:1 and C18:1 fatty acids contents) the deep and surface isolates were clearly separated into two clusters. Distinctions between them were also found in different lectin binding capacity, which is probably determined by the structure of their extracellular polysaccharide matrix. Analysis of the results of PCR with primers to repeated nucleotide sequences revealed a higher level of genetic polymorphism in surface strains in comparison with the deep isolates. This division was confirmed by the cluster analysis method though it was not as clear as in the fatty acids analysis. The described peculiarities are probably reflective of specific conditions in which A. macleodii strains live on the surface or in the depth of the world's oceans.