Caulobacter crescentus


Caulobacter crescentus

Taxobox
color = lightgrey
name = "Caulobacter crescentus"
regnum = Bacteria
phylum = Proteobacteria
classis = Alpha Proteobacteria
ordo = Caulobacterales
familia = Caulobacteraceae
genus = "Caulobacter"
species = "C. crescentus"
binomial = "Caulobacter crescentus"
binomial_authority = Poindexter 1964

"Caulobacter crescentus" is a Gram-negative, oligotrophic bacterium widely distributed in fresh water lakes and streams. It plays an important role in the carbon cycle.

"Caulobacter" is an important model for study of the regulation of the cell cycle and cellular differentiation. "Caulobacter" daughter cells are very different from each other. One is a mobile "swarmer" cell that has a flagellum for swimming. The other, called the "stalked" cell has a long tubular stalk structure protruding from one pole that has an adhesive holdfast material on its end, with which the stalked call can adhere to surfaces. Chromosome replication and cell division only occurs in the stalked cells. Swarmer cells differentiate into stalked cells as they mature. Often surviving in nutrient-poor environs, "Caulobacter crescentus" is a Gram-negative bacterium ubiquitous in fresh water, soil, and sea water. "C. crescentus" exhibits a dimorphic life cycle that most likely provides an advantage in such competitive environments. The stalk cell can attach to a surface, while the swarmer cell can search for nutrients. The adhesive material of the holdfast has been reported to be one of the strongest natural glues.

trains and Distribution

In the laboratories they distinguish between the Caulobacter crescentus strain CB-15 (the strain found in nature) and NA-1000 (the laboratory-sdopted strain).There are several differences between the two strains, which are not yet fully undestood.

Physiology and Life Cycle

Genomics

Genetics and Molecular Biology

Normal Role

Model Organism

Caulobacter Cell Cycle

Because of its easy manipulation in laboratory, "Caulobacter" has become a model organism to investigate cell cycle regulation in bacteria. Of "Caulobacter"'s 3767 protein-coding genes, about 550 are regulated in a cell-cycle-dependent manner, in large part by three regulatory proteins: CtrA, GcrA and DnaA, which together control the expression of 185 cell-cycle regulated genes. CtrA upregulates the expression of many genes involved in cell division: DNA methylation, flagella, stalk, and septal Z-ring biogenesis. In addition, CtrA binds to five DNA sites that overlap with the binding sites of the replication initiation protein, DnaA, and thereby precludes a new round of DNA replication. Furthermore, CtrA inhibits the expression of GcrA, which functions as an activator of components of the replisome and the segregation machinery.

Based on experimental evidence, the 'CtrA - bistable' switch mechanism [http://mpf.biol.vt.edu/research/caulobacter/pp/mechanism.php] is proposed for cell cycle control in this bacterium [cite journal |quotes= |last=Brazhnik |first=Paul |authorlink= |coauthors=Tyson, John|year=2006 |month= |title=Cell cycle control in bacteria and yeast: a case of convergent evolution? |journal=Cell Cycle |volume=5 |issue=5 |pages=522–9 |doi= |id= |url=http://www.landesbioscience.com/journals/cc/abstract.php?id=2493 |accessdate= ] . A mathematical model [http://mpf.biol.vt.edu/research/caulobacter/pp/index.php] was constructed to interpret the detailed temporal dynamics of regulatory gene expression during the cell cycle and differentiation process of wild-type cells as well as several mutant strains. [cite journal |quotes= |last=Li |first=Shenghua |authorlink= |coauthors=Brazhnik, Paul, Sobral, Bruno and Tyson, John|year=2008 |month= |title=A Quantitative Study of the Division Cycle of "Caulobacter crescentus" Stalked Cells |journal=PLoS Computational Biology |volume=4 |issue=1 |pages=e9 |doi=10.1371/journal.pcbi.0040009 |id= |url=http://compbiol.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pcbi.0040009 |accessdate= ] This model presents a unified view of temporal and spatial regulation of protein activities during the asymmetric cell division cycle of "Caulobacter". It also helps to interpret phenotypes of known mutants, and predicts novel ones.

Caulobacter Aging

"Caulobacter" was the first asymmetric bacterium shown to age. Reproductive senescence was measured as the decline in the number of progeny produced over time. [ cite journal |last=Ackermann |first=Martin |coauthors=Stephen C. Stearns, Urs Jenal |title=Senescence in a bacterium with asymmetric division |url=http://www.sciencemag.org/cgi/content/full/300/5627/1920?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Senescence+in+a+Bacterium+with+Asymmetric+Division+&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT |journal=Science |volume=300 |issue=5627 |date=2003 |pages=1920 |doi=10.1126/science.1083532 |pmid=12817142 ] [cite journal |last=Ackermann |first=Martin |coauthors=Alexandra Schauerte, Stephen C. Stearns, Urs Jenal |title=Experimental evolution of aging in a bacterium|doi= |journal=BMC Evolutionary Biology |volume=7 |issue=126 |date=2007 |pages= ] A similar phenomenon has since been described in the bacterium "Escherichia coli", which gives rise to morphologically similar daughter cells. [cite journal |quotes= |last=Stewart |first=Eric J. |authorlink= |coauthors=Richard Madden, Gregory Paul, Francois Taddei |year=2005 |month= |title=Aging and death in an organism that reproduces by morphologically symmetric division |journal=PLoS Biology |volume=3 |issue=2 |pages=e45 |doi=10.1371/journal.pbio.0030045 |id= |url=http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0030045 |accessdate= ]

Role in Biotechnology

References

External links

* [http://mpf.biol.vt.edu/research/caulobacter/pp/index.php Mathematical modeling of cell division cycle control in "Caulobacter crescentus"]
* [http://mpf.biol.vt.edu/Research.html Cell cycle modeling]
* [http://www.livescience.com/animalworld/060410_nature_glue.html World’s Strongest Glue! Available Only From Nature!]
* [http://www.nature.com/news/2006/060410/full/060410-1.html Bacterium makes nature's strongest glue]


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