English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Background  In spite of their abundance and importance, little is known about cyanobacterial cell biology and their cell cycle. During each cell cycle, chromosomes must be separated into future daughter cells, i.e. into both cell halves, which in many bacteria is achieved by an active machinery that operates during DNA replication. Many cyanobacteria contain multiple identical copies of the chromosome, but it is unknown how chromosomes are segregated into future daughter cells, and if an active or passive mechanism is operative. In addition to an outer and an inner cell membrane, cyanobacteria contain internal thylakoid membranes that carry the active photosynthetic machinery. It is unclear whether thylakoid membranes are invaginations of the inner cell membrane, or an independent membrane system.    Results  We have used different fluorescent dyes to study the organization of chromosomes and of cell and thylakoid membranes in live cyanobacterial cells. FM1-43 stained the outer and inner cytoplasmic membranes but did not enter the interior of the cell. In contrast, thylakoid membranes in unicellular  Synechocystis  cells became visible through a membrane-permeable stain only. Furthermore, continuous supply of the fluorescent dye FM1-43 resulted in the formation of one to four intracellular fluorescent structures in  Synechocystis  cells, within occurred within 30 to 60 minutes, and may represent membrane vesicles. Using fluorescent DNA stains, we found that  Synechocystis  genomic DNA is compacted in the cell centre that is devoid of thylakoid membranes. Nucleoids segregated very late in the cell cycle, just before complete closing of the division septum. In striking contrast to  Bacillus subtilis , which possesses an active chromosome segregation machinery, fluorescence intensity of stained nucleoids differed considerably between the two  Synechocystis  daughter cells soon after cell division.    Conclusion  Our experiments strongly support the idea that the cytoplasmic and thylakoid membranes are not directly connected, but separate entities, in unicellular cyanobacteria. Our findings suggest that a transport system may exist between the cytoplasmic membrane and thylakoids, which could mediate the extension of thylakoid membranes and possibly also protein transport from the cytoplasmic membrane to thylakoid membranes. The cell cycle studies in  Synechocystis  sp. PCC 6803 show that the multiple chromosome copies per cell segregate very late in the cell cycle and in a much less stringent manner than in  B. subtilis  cells, indicating that chromosomes may become segregated randomly and in a passive fashion, possibly through constriction of the division septum.

bmc cell biology

Fluorescence staining of live cyanobacterial cells suggest non-stringent chromosome segregation and absence of a connection between cytoplasmic and thylakoid membranes