Ribulose 1,5-bisphosphate carboxylase and oxygenase from Thiocapsa roseopersicina: activation and catalysis

The Complete Genome of a Novel Typical Species Thiocapsa bogorovii and Analysis of Its Central Metabolic Pathways

The purple sulfur bacterium Thiocapsa roseopersicina BBS is interesting from both fundamental and practical points of view. It possesses a thermostable HydSL hydrogenase, which is involved in the reaction of reversible hydrogen activation and a unique reaction of sulfur reduction to hydrogen sulfide. It is a very promising enzyme for enzymatic hydrogenase electrodes. There are speculations that HydSL hydrogenase of purple bacteria is closely related to sulfur metabolism, but confirmation is required. For that, the full genome sequence is necessary. Here, we sequenced and assembled the complete genome of this bacterium. The analysis of the obtained whole genome, through an integrative approach that comprised estimating the Average Nucleotide Identity (ANI) and digital DNA-DNA hybridization (DDH) parameters, allowed for validation of the systematic position of T. roseopersicina as T. bogorovii BBS. For the first time, we have assembled the whole genome of this typical strain of a new bacterial species and carried out its functional description against another purple sulfur bacterium: Allochromatium vinosum DSM 180T. We refined the automatic annotation of the whole genome of the bacteria T. bogorovii BBS and localized the genomic positions of several studied genes, including those involved in sulfur metabolism and genes encoding the enzymes required for the TCA and glyoxylate cycles and other central metabolic pathways. Eleven additional genes coding proteins involved in pigment biosynthesis was found.

Molecular and cellular regulation of autotrophic carbon dioxide fixation in microorganisms

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Carbon dioxide assimilation in cyanobacteria: regulation of ribulose, 1,5-bisphosphate carboxylase

Cyanobacteria assimilate carbon dioxide through the Calvin cycle and therefore must regulate the activity of ribulose 1,5-bisophosphate carboxylase. Using an in situ assay, as well as measuring the activity in crude, partially purified, and homogeneous preparations, we can show that a number of phosphorylated intermediates exert a regulatory role. Three diverse organisms, Agmenellum quadruplicatum, Aphanocapsa 6714, and Anabaena sp. CA, were studied, and it was found that the in situ and cell-free carboxylase activities were particularly affected by low levels of phosphogluconate and reduced nicotinamide adenine dinucleotide phosphate. There was a marked activation by these ligands when the inactive enzyme was assayed in the presence of low levels of bicarbonate, a result significantly different from a previous report. Moreover, the fully activated enzyme was inhibited by phosphogluconate. In situ Anabaena CA carboxylase activity exhibited a particular capacity for activation by phosphogluconate and reduced nicotinamide adenine dinucleotide phosphate. However, activation of the crude, partially purified, or homogeneous Anabaena CA carboxylase by phosphogluconate and reduced nicotinamide adenine dinucleotide phosphate was significantly decreased when compared with enzyme activity in permeabilized cells. It appears that the microenvironment or the conformation of the enzyme within the cell may be significantly different from that of the isolated enzyme.