Onyshchenko O. Taxonomy and antibiotic activity of Alteromonas-like bacteria from the Black Sea

The thesis is dedicated to study of the Black Sea Alteromonas-like bacteria, investigation of their phenotypic characteristics and elucidation of their antibiotic activity against the test strains of bacteria, yeast, microfungy and cyanobacteria. The polyphasic taxonomic analysis of the Black Sea Alteromonas-like bacteria has been carried out using the modern systematics methods and complex study of the wide spectrum of biological properties of the isolates. Scheme of stepwise selection of Alteromonas-like bacteria from 384 strains of microorganisms isolated from the Black Sea water, algae and invertebrates has been elaborated on the base of main differential features of these bacteria. Gram negative, oxidase positive, arginine dihydrolase negative, nonfermenting rods motile with one polar flagellum and requiring sodium ions for growth have been selected according to this scheme. Numeric classification of the Black Sea Alteromonas-like bacteria has been executed on the base of complex study of 97 phenotypic features of the isolates as well as of the type strains of genera Pseudoalteromonas, Marinomonas, Alteromonas и Shewanella. Studied strains have been preliminary classified as P. nigrifaciens, P. citrea, P. haloplanktis, A. macleodii, Pseudoalteromonas sp. Results of 16S rRNA sequencing have confirmed the presence of Alteromonas macleodii, Pseudoalteromonas citrea, P. haloplanktis representatives among the studied isolates and have shown presence of Shewanella baltica, S. colwelliana, "Marinomomas protea" representatives and single strains of some other taxa (Halomonas variabilias, Psychrobacter glacincola, Aeromonas popoffii).Genetic analysis has shown the presence of some new taxa in the Black Sea water. These were a new genus genetically related to Oceanospirillum linum and new species of Pseudoalteromonas genus. The investigation of the wide nutritional spectra of Alteromonas-like bacteria confirmed significant variability of their characteristics as well as phenotypic similarity of genera Alteromonas, Pseudoalteromonas, Marinomonas and Shewanella. A set of characters typical for each genus has been proposed for the Alteromonas-like bacteria differentiation scheme. The of the Black Sea isolates susceptibility to wide set of antibiotics has shown the possibility of including these characteristics into the diagnostic keys. Most of Alteromonas-like bacteria have been isolated from the Black Sea water and invertebrates but not from algae. Representatives of Marinomonas and Alteromonas have been isolated only from the sea water samples; bacteria of Pseudoalteromonas (43 %) and Shewanella (38 %) were associative with marine invertebrates.The antibiotic producing strains have been found for the first time among Shewanella and Alteromonas representatives. The cultural liquid of Alteromonas macleodii 9 inhibited growth of Staphylococcus aureus, Bacillus subtilis and phytopathogenic fungi. So study of the Black Sea Alteromonas-like bacteria taxonomy and antibiotic activity enlarged the data concerning biodiversity and biological properties of halophilic marine bacteria of this sea both as a specific basin and a part of the world ocean. Key words: Alteromonas-like bacteria, genus Pseudoalteromonas, Alteromonas, Shewanella, Marinomonas, taxonomic analysis, antibacterial, antifungal, algaecide activity of marine bacteria.