Экосистемы рисовых полей являются хорошим источником новых штаммов гетероцистных цианобактерий, пригодных для применения в биотехнологических системах продукции фотоводорода. Изучены морфологические и физиологические свойства двух новых эпифитных штаммов цианобактерий – Anabaena sp. 182 и Anabaena sp. 281. Проведено ДНК-типирование этих штаммов на основе ПЦР-амплификации генов гидрогеназ и ДНК-анализа с RAPD- и Rep-праймерами. Штамм Anabaena sp. 281 по геномным характеристикам существенно отличается от двух референтных штаммов с секвенированными геномами (Anabaena variabilis ATСС 29413 и Nostoc sp. PCC 7120), тогда как штамм Anabaena sp. 182 является близкородственным штамму A. variabilis ATСС 29 413. Благодаря ряду физиологических и биохимических преимуществ штамм Anabaena sp. 182 может рассматриваться в качестве нового перспективного объекта генетических и генно-инженерных исследований, направленных на создание продуцентов молекулярного водорода.

Ecosystems of rice paddies are good sources of new strains of heterocyst-forming cyanobacteria that can be used in biotechnological systems for production of photohydrogen. The morphological and physiological properties of two novel epiphytic strains of cyanobacteria, Anabaena sp. 182 and Anabaena sp. 281, were studied. DNA typing of these strains based on PCR amplification of hydrogenase-encoding genes and DNA analysis using RAPD and Rep primers was carried out. The properties of the genome of strain Anabaena sp. 281 differed considerably from those of two reference strains (Anabaena variabilis ATCC 29413 and Nostoc sp. PCC 7120) with sequenced genomes, whereas strain Anabaena sp. 182 was found to be a close relative of A. variabilis ATCC 29413. Due to a number of physiological and biochemical advantages, Anabaena sp. 182 may be considered a new promising model for molecular and genetic engineering studies aimed at the development of H2 producers.

Peculiarities of indole-3-acetic acid (IAA) biosynthesis in saprophytic plant-associated Agrobacterium radiobacter 5D-1 were studied. Synthesis of IAA by this bacterium was found to be controlled by chromosomal genes; it was tryptophan-dependent and occurred, most likely, via the formation of indole-3-pyruvic acid, since it was inhibited by ammonium and glutamine and could not proceed when indole-3-acetamide was supplied as a precursor instead of tryptophan. Mutants of strain 5D-1 with impaired IAA synthesis were isolated. Their culture liquid contained less IAA (30-40% of the IAA production by the parent strain) and unidentified indole-containing compounds that exhibited an absorption maximum at 485 nm staining in the Sal'kovskii reaction. These mutants can be used for conclusive elucidation of the IAA biosynthesis pathway in A. radiobacter and mechanisms of its genetic control.

Mutants with altered capacity for interaction with plants or nitrogen fixation were obtained through ethyl methanesulfonate and transposon Tn5 induction in Agrobacterium radiobacter 5D-1, a saprophytic nitrogen-fixing bacterium capable of associative interaction with plants. The former mutants were selected on a medium containing calcofluor, and the latter mutants were isolated on a medium with tetrazolium bromide. Mutants whose interaction with the plant roots was impaired (Cal(-) and Cal(++)) differed from the wild strain in the activity of nitrogenase when grown in association with rape. When grown in a monoculture, the activity of nitrogenase was unchanged. In mutants with disturbances of nitrogen metabolism (Nm and Nr), clones were found with alterations in acetylene reduction efficiency. These alterations are manifested either in a similar or in a reverse way in a monoculture and in association with rape. The properties of the obtained mutants suggest that mutations occur in the genes which exert control over nitrogen fixation realized in association with a plant.

Two classes of Rhodobacter sphaeroides mutants with Nif(c) phenotype were studied. Synthesis and activity of nitrogenase in these mutants are not regulated by ammonia ions. Glutaminesynthetase activity is abolished in mutants of the first class (Gln-phenotype). This defect is caused by a mutation within the glnB-glnA operon. The glutaminesynthetase activity is significantly diminished in Drn mutants of the second class, as compared with that of wild type cells. However, they are prototrophs, and the Nif(c) phenotype is caused by mutations localized outside the glnB-glnA operon. The most important feature of Drn mutants is lack of nitrogenase synthesis in the dark. Based on these data, the existence of two systems of nitrogenase synthesis activation in R. sphaeroides may be postulated. The first one is light-dependent, while the second is not. In the Drn mutants, the mutations affected the gene (or genes) controlling the system of light-independent activation of nitrogenase synthesis. The lack of nitrogenase synthesis and activity regulation in the Gln- and Drn mutants is most likely related with the repression of the ammonia ion transport system.

Mutants of phototrophic bacterium Rhodopseudomonas sphaeroides deficient in nitrogen fixation and unable to utilize alanine, proline, arganine and glutamic acid as nitrogen sources have been obtained as a result of nitrosomethylurea mutagenesis. The majority of the nif-mutants have no nitrogenase activity and aminotransferase activity of glutamine synthetase during their growth in glutamine containing medium is sharply lowered. The specific activity of glutamate synthase and alanine dehydrogenase in the mutants does not differ from that of the wild type strain. One of the mutants (NF-42) has higher glutamine synthetase activity in comparison with the wild type strain. The pleiotropic character of the changes obtained in the nif-mutants shows that the loss of nitrogen fixation ability is due to defects in regulation system of nitrogen metabolism.