[Rhodopseudomonas sphaeroides mutants defective in nitrogen fixation]. / Mutanty Rhodopseudomonas sphaeroides, defektnye po azotfiksatsii.

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.

[Electron absorption and fluorescence spectra of carbonyl--conjugated pentaenes in various media]. / Elektronnye spektry pogloshcheniia i fliuorestsentsii karbonil--kon"iugirovannykh pantaenov v razlichnykh sredakh.

It was found that fluorescence intensity of carbonyl-conjugated pentaens of flavofungin flavopentin and brunefungin in solutions depended on the solvent polarity and specific interactions of the antibiotics with the solvents. Addition of cholesterol into the aqueous solutions of these antibiotics resulted in a hypsochrome shift in their absorption spectra and increased fluorescence intensity. The antibiotics were found by their fluorescence in the yeast cells sensitive to them when their content was close to the concentrations resulting in the cell lysis. Low concentrations of the antibiotics resulted in changed localization of the yeast self fluorescence.