Biomedical subjects

O A Koksharova

Publications and source records attributed to O A Koksharova.

4 recordsLinked to original sources

PubMed2002

Genetic tools for cyanobacteria.

Cyanobacteria are oxygenic photosynthetic bacteria that have been used increasingly to study diverse biological processes, including photosynthesis and its regulation; cell differentiation and N2 fixation; metabolism of nitrogen, carbon, and hydrogen; resistance to environmental stresses; and molecular evolution. Many vectors and other genetic tools have been developed for unicellular and filamentous strains of cyanobacteria. Transformation, electroporation, and conjugation are used for gene transfer. Diverse methods of mutagenesis allow the isolation of many sought-for kinds of mutants, including site-directed mutants of specific genes. Reporter genes permit measurement of the level of transcription of particular genes, and assays of transcription within individual colonies or within individual cells in a filament. Complete genomic sequences have been obtained for the unicellular cyanobacterium, Synechocystis sp. strain PCC 6803 and the filamentous, heterocyst-forming cyanobacterium, Anabaena sp. strain PCC 7120. Genomic sequence projects are under way for Nostoc punctiforme strain PCC 73102 (ATCC 29133) and strains of the unicellular genera, Synechococcus, Prochlorococcus, and Gloeobacter. Genomic sequence data provide the opportunity for global monitoring of changes in genetic expression at transcriptional and translational levels in response to variations in environmental conditions. The availability of genomic sequences accelerates the identification, study, modification and comparison of cyanobacterial genes, and facilitates analysis of evolutionary relationships, including the relationship of chloroplasts to ancient cyanobacteria. The many available genetic tools enhance the opportunities for possible biotechnological applications of cyanobacteria.

Bacterial Proteins↗

PubMedDate not supplied

[The gap1 operon of the cyanobacterium Synechococcus PCC 7942 carries a gene encoding glycogen phosphorylase and is induced under anaerobic conditions].

The cloning and sequencing of the gap1 operon, which encodes the glycolytic NAD-specific glyceraldehyde-3-phosphate dehydrogenase in the cyanobacterium Synechococcus PCC 7942, showed that the gap1 gene is closely linked to the glgP gene encoding glycogen phosphorylase (an enzyme that catalyzes the first step of glycogen degradation). Northern blotting experiments showed that the gap1 and glgP genes are co-expressed and organized in a bicistronic operon, whose expression is enhanced under anaerobic conditions. The nucleotide sequence of the operon has been submitted to GenBank under accession number AF428099.

Anaerobiosis↗

PubMedDate not supplied

[The gap3 gene of Synechococcus PCC 7942 is induced during adaptation to low CO2 concentrations].

The gap3 genes of the Synechococcus and Anabaena cyanobacteria fulfill so far unknown function. A homolog of this gene has recently been found in the nuclear genomes of diplonemids, which are heterotrophic flagellates closely related to kinetoplastids and euglenoids. To understand the function of the gap3 gene in the cyanobacteria, we performed Northern blotting experiments with the gap3 probes under different growth conditions. Under the standard photosynthetic growth conditions (high illumination and 1% CO2 in the gas phase), the expression of the gap3 gene was very low, but significantly increased during cell adaptation to the low CO2 concentration (0.03%). The gap3 operon was expressed as a polycistronic transcript of about 7 kb in size, which included ORF2 (1259 bp) immediately downstream of gap3. ORF2 probably encodes a putative transporter of HCO3. The nucleotide sequence of ORF2 has been submitted to GenBank under accession number AF 428100.

Adaptation, Physiological↗

PubMedDate not supplied

[The first protein map of Synechococcus sp. strain PCC 7942].

The first protein map was developed of Synechococcus sp. strain PCC 7942, a model organism for studies of photosynthesis, prokaryotic circadian rhythms, cell division, carbon-concentrating mechanisms, and adaptive responses to a variety of stresses. The proteome was analyzed by two-dimensional gel electrophoresis with subsequent MALDI-TOF mass spectroscopy and database analysis. Of the 140 analyzed protein spots, 110 were successfully identified as 62 different proteins, many of which occurred as multiple spots on the gel. The identified proteins participate in the major metabolic and cellular processes in cyanobacterial cells during the exponential growth phase. In addition, 14 proteins which were previously either unknown or considered to be hypothetical were shown to be true gene products in Synechococcus sp. strain PCC 7942. These results may be helpful for the annotation of the recently sequenced genome of this cyanobacterium, as well as for biochemical and physiological studies of Synechococcus.

Bacterial Proteins↗