Polyhydroxybutyrate production from carbon dioxide by cyanobacteria.

Genetic characterization and enhancement of polyhydroxybutyrate (PHB) accumulation in cyanobacteria were investigated for efficient PHB production from CO2. The genome DNAs in the PHB-accumulating strains Synechococcus sp. MA19 and Spirulina platensis NIES46 retained the highly homologous region to phaC of Synechocystis PCC6803, whereas low homology was detected in the nonaccumulating strains Synechococcus sp. PCC7942 and Anabaena cylindrica NIES19. Synechococcus sp. MA19, which accumulates PHB up to 30% of dry cell weight from CO2 as the sole carbon source, was mutated by insertion of transposon Tn5 to enhance the PHB accumulation. Genetic and physiological analysis of the mutant indicated that decreased phosphotransacetylase activity could trigger an increase of acetyl coenzyme A leading to enhancement of PHB accumulation. PHB synthase in Synechococcus sp. MA19 was probably attached to thylakoid membrane since PHB granules were associated with pigments. A genetically engineered cyanobacteria retaining soluble PHB synthase from Ralstonia eutropha accumulated pigment-free PHB granules, which is an advantage for the purification of PHB.

Enhanced hydrogen production by a mutant of Rhodobacter sphaeroides having an altered light-harvesting system.

A stable mutant of the photosynthetic bacterium Rhodobacter sphaeroides with an altered light-harvesting (LH) system (P3 mutant) was obtained by UV irradiation and characterized. The mutant exhibited a 2.7-fold decrease in the core antennal (LH1) content and 1.6-fold increase in peripheral antennal (LH2) content compared to the wild-type strain. The H2 evolution rates in the P3 mutant under 800- and 850-nm light, corresponding to the absorption maxima of LH2, were 1.5 times higher than in the wild-type strain. The wild-type absorption spectrum was restored in the P3 mutant when a 1.1-kb PCR-amplified fragment containing the puf promoter and pufQBA genes was ligated into a pRK-415 derivative and introduced into it. The transformant showed lower H2 production rates at 800 and 850 nm than the P3 strain carrying the control plasmid, indicating that the accelerated H2 production in the P3 mutant was a result of alterations in the LH system.

[A new method for urea detection in biological fluids]. / Novyi metod dlia opredeleniia soderzhaniia mocheviny v biologicheskikh zhidkostiakh.

A modified urease hypochlorite method for measuring urea in biological fluids is described. Its novel feature is the use of 4-hydroxycoumarin as ammonia acceptor. This compound has never been used for this purpose, and it has a number of advantages over traditional phenol and its derivatives: the measurement is performed in just two steps, the compound is nontoxic and used in low concentrations, and the accuracy of measurements is higher due to decrease of the systemic error. Results of urea tests with the new kit are presented. The kit contains ready-to-use components in tablets and stabilized concentrated solutions of sodium hypochlorite and alkali. The characteristics of the kit are as follows: linearity of determination up to 25 mmoles per liter, deviation from linearity no more than 7%, and sensitivity up to 0.7 mmoles/liter.