Burkholderia cepacia: Difference between revisions

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==Genome structure==
==Genome structure==
The replicon number and sizes vary from strain to strain in ''Burkholderia cepacia'' species.  The largest replicon is found in strain N2P5 (9.3 Mb).  Most species contain 2 to 4 large replicons, and many also contain smaller replicons as well.  Many species contain plasmids and, all species have circular chromosomes.  The ''Burkholderia cepacia'' type- strain ATCC 25416 (genomovar I) is 8.1 Mb in length and is known to have four circular replicons.  Its largest replicon contains 4 rrn operons and the other two megabase- sized replicons contain a single rrn operon each.  From this information it can be inferred that the organism has three chromosomes and one large plasmid. (6)
The replicon number and sizes vary from strain to strain in ''Burkholderia cepacia'' species.  The largest replicon is found in strain N2P5 (9.3 Mb).  Most species contain 2 to 4 large replicons, and many also contain smaller replicons as well.  Many species contain plasmids, and all species have circular chromosomes.  The ''Burkholderia cepacia'' type- strain ATCC 25416 (genomovar I) is 8.1 Mb in length and is known to have four circular replicons.  Its largest replicon contains 4 rrn operons and the other two megabase- sized replicons contain a single rrn operon each.  From this information it can be inferred that the organism has three chromosomes and one large plasmid. (6)


==Cell structure and metabolism==
==Cell structure and metabolism==

Revision as of 21:27, 4 June 2007

A Microbial Biorealm page on the genus Burkholderia cepacia

Classification

Higher order taxa

Bacteria; Proteobacteria; Betaprotebacteria; Burkholderiales; Burkholderiaceae; Burkholderia

Species

NCBI: Taxonomy

The Burkholderia cepacia complex consists of nine genomic species called genomovars: B. cepacia, B. multivorans, B. cenocepacia, B. vietnamiensis, B. stabilis, B. ambifaria, B. dolosa, B. anthina, and B. pyrrocinia.

Description and significance

Burkholderia cepacia was first described by Walter Burkholder of Cornell University in 1949 when he determined it to be the cause of bacterial rot of onion bulbs. It was originally named Pseudomonas cepacia and was later changed to its current name. Burkholderia cepacia refers to a complex of nine closely related species listed above. They are rod-shaped, free-living, motile Gram- negative bacteria ranging from 1.6- 3.2 μm. They have been found to possess multitrichous polar flagella as well as pili used for attachment. Burkholderia cepacia can be found in soil, water, and infected plants, animals, and humans. Aside from being a plant and human pathogen it has many significant agricultural uses. It is capable of breaking down toxic compounds found in pesticides and herbicides. It has also been noted to repress certain soil-borne pathogens and is being considered as an agent for promoting crop growth.

The appearance of Burkholderia cepacia species varies based on the strain and the culture medium used. Three media are currently being used to isolate the bacteria. They are the following: Pseudomonas cepacia agar (PCA), oxidation fermentation polymyxin bacitracin lactose agar (OFBL), and Burkholderia cepacia selective agar (BCA). The last medium has proved to be the most effective since it actually suppresses the growth of non-Burkholderia cepacia bacteria. Burkholderia cepacia bacteria will form visible pinpoint colonies within 24 hours, and the colonies appear to be smooth and somewhat elevated.

Genome structure

The replicon number and sizes vary from strain to strain in Burkholderia cepacia species. The largest replicon is found in strain N2P5 (9.3 Mb). Most species contain 2 to 4 large replicons, and many also contain smaller replicons as well. Many species contain plasmids, and all species have circular chromosomes. The Burkholderia cepacia type- strain ATCC 25416 (genomovar I) is 8.1 Mb in length and is known to have four circular replicons. Its largest replicon contains 4 rrn operons and the other two megabase- sized replicons contain a single rrn operon each. From this information it can be inferred that the organism has three chromosomes and one large plasmid. (6)

Cell structure and metabolism

Burkholderia cepacia is capable of growing on over 200 organic compounds. It is incredibly versatile in this regard. Of special interest is its ability to use the chlorinated aromatic compound 2,4,5- trichlorophenoxyacetic acid as a source of carbon and energy (4). This compound is found in many pesticides and herbicides. Some of B. cepacia’s cell structures include polar flagella used for motility and pili used in adhesion. Burkholderia cepacia complex species may express one of two flagellin types that differ in size. Type I is 55 kDa and type II is 45 kDa. Aside from motility, flagella have also been noted to function in adhesion, the production of biofilms, and in the production of an inflammatory response in the host. (5)

Ecology

Burkholderia cepacia complex species are soil-dwelling bacteria commonly found on plant roots. They are of significant environmental interest. Along with their antinematodal and antifungal properties, they can also degrade a large variety of toxic compounds. This makes them extremely useful in bioremediation, a practice using biological compounds to remove hazardous compounds and pollutants. Chlorinated phenols and phenoxyacetates are commonly used in agriculture as pesticides, herbicides, and preservatives. They compose a major group of recalcitrant environmental pollutants. Burkholderia cepacia has the ability to use these compounds as a source of carbon and energy therefore breaking them down and removing them from the environment (4).

Pathology

Burkholderia cepacia has long been known as both a plant and human pathogen. In humans it is most well known for its infection in cystic fibrosis patients as well as other patients with compromised immune systems. All species within the Burkholderia cepacia complex have been isolated from cystic fibrosis patients, however genomovar III and Burkholderia multivorans seem to cause the majority of infections. (7) There is still much to be learned about the virulence factors used by Burkholderia cepacia. There is evidence that one species, Burkholderia cenocepacia (genomovar III), actually uses quorum sensing to control the expression of its virulence factors which means its pathogenicity is only expressed when a high enough population density exists to take over the host before it can mount a response. (8) There is a high mortality rate in patients infected with Burkholderia cepacia. Many develop what is known as cepacia syndrome. This is a “necrotizing pneumonia with bacteremia which leads to an acute and frequently fatal clinical decline.”

Application to Biotechnology

Current Research

References

1.) Miller SC, LiPuma JJ, Parke JL “Culture based and Non-Growth Dependent Detection of the Burkholderia cepacia complex in Soil Environments” Applied Environmental Microbiology, August 2002

2.) Barbara A. Hales, J. Alun W. Morgan, C. Anthony Hart, Craig Winstanley “Variation in Flagellin Genes and Proteins in Burkholderia cepacia”

3.) P. Wigley, N. F. Burton “Multiple Chromosomes in Burkholderia cepacia and Burkholderia gladioli and their distribution in clinical and environmental strains of B. cepacia” Journal of Applied Microbiology, Volume 88 Issue 5

4.) Department of Microbiology and Immunology, College of Medicine, University of Illinois; “Genes for 2,4,5- Trichlorophenoxyacetic Acid Metabolism in B. cepacia AC1100"

5.) Teresa A. Uirban, Adam Griffith, Anastasia M. Torok, Mark E. Smolkin, Jane L. Burns, Joanna B. Goldberg. Infect. Immun. 2004 September. Contribution of Burkholderia cenocepacia Flagella to Infectivity and Inflammation

6.) Rodly PD, Romling U, Tummler B. “A Physical genome map of the Burkholderia cepacia type strain” Mol. Microbiology 1995; 17:57-67

7.) Andrew McDowell, Eshwar Mahenthiralingam, John E. Moore, Kerstin E. A. Dunbar, A Kevin Webb. “PCR-Based Detection and Identification of Burkholderia cepacia Complex Pathogens in Sputum from Cystic Fibrosis Patients” J Clin Microbiol. 2001 December

8.) Shawn Lewenza, Barbara Conway, E. P. Greenberg, Pamela A, Sokol. “Quorum Sensing in Burkholderia cepacia: Identification of the LuxRI Homologs CepRI” Journal of Bacteriology 1999 February 181(3): 748-756


Edited by student of Rachel Larsen and Kit Pogliano