Metabolic analysis reveals the contribution of mechanosensitive channel MscM to extracellular release of glutamate in glycogen-deficient Synechococcus elongatus.

In bacteria, mechanosensitive channels mediate extracellular release of osmolytes, including glutamate, functioning as safety valves upon osmotic downshift. In cyanobacteria, the role of mechanosensitive channels has not been completely elucidated. Recently, the glycogen-deficient ΔglgC mutant of Synechococcus elongatus PCC 7942 was found to release glutamate extracellularly, giving rise to a hypothesis that the role of mechanosensitive channels in cyanobacteria is conserved.

Discovery of novel replication proteins for large plasmids in cyanobacteria and their potential applications in genetic engineering.

Numerous cyanobacteria capable of oxygenic photosynthesis possess multiple large plasmids exceeding 100 kbp in size. These plasmids are believed to have distinct replication and distribution mechanisms, as they coexist within cells without causing incompatibilities between plasmids. However, information on plasmid replication proteins (Rep) in cyanobacteria is limited.

Glycogen deficiency enhances carbon partitioning into glutamate for an alternative extracellular metabolic sink in cyanobacteria.

Glycogen serves as a metabolic sink in cyanobacteria. Glycogen deficiency causes the extracellular release of distinctive metabolites such as pyruvate and 2-oxoglutarate upon nitrogen depletion; however, the mechanism has not been fully elucidated. This study aimed to elucidate the mechanism of carbon partitioning in glycogen-deficient cyanobacteria.

Relationship between Cell Cycle and Diel Transcriptomic Changes in Metabolism in a Unicellular Red Alga.

Metabolism, cell cycle stages, and related transcriptomes in eukaryotic algae change with the diel cycle of light availability. In the unicellular red alga , the S and M phases occur at night. To examine how diel transcriptomic changes in metabolic pathways are related to the cell cycle and to identify all genes for which mRNA levels change depending on the cell cycle, we examined diel transcriptomic changes in In addition, we compared transcriptomic changes between the wild type and transgenic lines, in which the cell cycle was uncoupled from the diel cycle by the depletion of either cyclin-dependent kinase A or retinoblastoma-related protein.

Evolutionary Changes in DnaA-Dependent Chromosomal Replication in Cyanobacteria.

Replication of the circular bacterial chromosome is initiated at a unique origin () in a DnaA-dependent manner in which replication proceeds bidirectionally from to . The nucleotide compositions of most bacteria differ between the leading and lagging DNA strands. Thus, the chromosomal DNA sequence typically exhibits an asymmetric GC skew profile.

Specific binding of DnaA to the DnaA box motif in the cyanobacterium Synechococcus elongatus PCC 7942.

In bacterial DNA replication, the initiator protein DnaA binds to the multiple DnaA box sequences located at oriC to facilitate the unwinding of duplex DNA strands. The cyanobacterium Synechococcus elongatus PCC 7942, which contains multiple chromosomal copies per cell, has DnaA box (like sequences around the oriC region, which is located upstream of dnaN. We previously observed the binding of DnaA around the oriC region; however, the DNA-binding specificity of DnaA to DnaA box sequences has not been examined.

Integration of a plasma membrane sugar transporter enables heterotrophic growth of the obligate photoautotrophic red alga .

The unicellular thermoacidophilic red alga is an emerging model organism of photosynthetic eukaryotes. Its relatively simple genome (16.5 Mbp) with very low-genetic redundancy and its cellular structure possessing one chloroplast, mitochondrion, peroxisome, and other organelles have facilitated studies.

Coordination of Polyploid Chromosome Replication with Cell Size and Growth in a Cyanobacterium.

Homologous chromosome number (ploidy) has diversified among bacteria, archaea, and eukaryotes over evolution. In bacteria, model organisms such as possess a single chromosome encoding the entire genome during slow growth. In contrast, other bacteria, including cyanobacteria, maintain multiple copies of individual chromosomes (polyploid).

Direct Visualization of the Multicopy Chromosomes in Cyanobacterium PCC 7942.

Cyanobacteria are prokaryotic organisms that carry out oxygenic photosynthesis. The fresh water cyanobacterium PCC 7942 is a model organism for the study of photosynthesis and gene regulation, and for biotechnological applications. Besides several freshwater cyanobacteria, 7942 also contains multiple chromosomal copies per cell at all stages of its cell cycle.

ParA-like protein influences the distribution of multi-copy chromosomes in cyanobacterium Synechococcus elongatus PCC 7942.

While many bacteria, such as Escherichia coli and Bacillus subtilis, harbour a single-copy chromosome, freshwater cyanobacteria have multiple copies of each chromosome per cell. Although it has been reported that multi-copy chromosomes are evenly distributed along the major axis of the cell in cyanobacterium Synechococcus elongatus PCC 7942, the distribution mechanism of these chromosomes remains unclear. In S.

Acidophilic green algal genome provides insights into adaptation to an acidic environment.

Some microalgae are adapted to extremely acidic environments in which toxic metals are present at high levels. However, little is known about how acidophilic algae evolved from their respective neutrophilic ancestors by adapting to particular acidic environments. To gain insights into this issue, we determined the draft genome sequence of the acidophilic green alga and performed comparative genome and transcriptome analyses between and its neutrophilic relative The results revealed the following features in that probably contributed to the adaptation to an acidic environment.

Variety of DNA Replication Activity Among Cyanobacteria Correlates with Distinct Respiration Activity in the Dark.

Cyanobacteria exhibit light-dependent cell growth since most of their cellular energy is obtained by photosynthesis. In Synechococcus elongatus PCC 7942, one of the model cyanobacteria, DNA replication depends on photosynthetic electron transport. However, the critical signal for the regulatory mechanism of DNA replication has not been identified.

A tightly inducible riboswitch system in Synechocystis sp. PCC 6803.

Cyanobacteria are photosynthetic microorganisms that serve as experimental model organisms for the study of photosynthesis, environmental stress responses, and the production of biofuels. Genetic tools for bioengineering have been developed as a result of such studies. However, there is still room for improvement for the tight control of experimental protein expression in these microorganisms.

Diversification of DnaA dependency for DNA replication in cyanobacterial evolution.

Regulating DNA replication is essential for all living cells. The DNA replication initiation factor DnaA is highly conserved in prokaryotes and is required for accurate initiation of chromosomal replication at oriC. DnaA-independent free-living bacteria have not been identified.

Intensive DNA Replication and Metabolism during the Lag Phase in Cyanobacteria.

Unlike bacteria such as Escherichia coli and Bacillus subtilis, several species of freshwater cyanobacteria are known to contain multiple chromosomal copies per cell, at all stages of their cell cycle. We have characterized the replication of multi-copy chromosomes in the cyanobacterium Synechococcus elongatus PCC 7942 (hereafter Synechococcus 7942). In Synechococcus 7942, the replication of multi-copy chromosome is asynchronous, not only among cells but also among multi-copy chromosomes.

DNA replication depends on photosynthetic electron transport in cyanobacteria.

The freshwater cyanobacterium Synechococcus elongatus PCC 7942 exhibits light-dependent growth. Although it has been reported that DNA replication also depends on light irradiation in S. elongatus 7942, the involvement of the light in the regulation of DNA replication remains unclear.

Light-dependent and asynchronous replication of cyanobacterial multi-copy chromosomes.

While bacteria such as Escherichia coli and Bacillus subtilis harbour a single circular chromosome, some freshwater cyanobacteria have multiple chromosomes p er cell. The detailed mechanism(s) of cyanobacterialreplication remains unclear. To elucidate the replication origin (ori ), form and synchrony of the multi-copy genome in freshwater cyanobacteria Synechococcus elongatus PCC 7942 we constructed strain S.