User:Seabuntin/Burkholderia cenocepacia

= Burkholderia cenocepacia = Burkholderia cenocepacia is a Gram-negative, rod-shaped bacterium that is commonly found in soil and water environments, typically in microaerophilic environments. The bacterium may also be associated with increased virulence in plants and animals, particularly as a human pathogen. It is one of over 20 species in the Burkholderia cepacia complex (Bcc) and is notable due to its virulence factors and inherent antibiotic resistance that render it a prominent opportunistic pathogen responsible for life-threatening, nosocomial infections in immunocompromised patients, such as those with cystic fibrosis or chronic granulomatous disease. Burkholderia cenocepacia may also cause disease in plants, such as in onions and bananas. Additionally, some strains serve as plant growth-promoting rhizobacteria.

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Adaptations

Able to survive under conditions with no oxygen

Taxonomy
Within the Burkholderia genus, the Burkholderia cepacia complex contains over 20 related species that cause opportunistic infections and possess antibiotic resistance. Burkholderia cepacia was originally defined as a single species, but it is now one of several species in the Bcc complex. Although closely related, the species within the Bcc complex have differing severity of pathogenicity, and B. cenocepacia is one of the most intensively studied due to its higher pathogenicity and antibiotic resistance compared to other species in the complex. Exchange of genetic material between species of the Bcc complex has resulted in a reticulated phylogeny that presents an obstacle to diagnostic classification at the species-level. Because of this phenotypic overlap between species, previous nomenclature of Bcc complex species involved genomovar terms, with Burkholderia cenocepacia categorized as genomovar III of the Bcc.

Genome
B. cenocepacia 's genome consists of three chromosomes and one plasmid. Chromosome 1 contains 3.87 Mb, chromosome 2 contains 3.22 Mb, and chromosome 3 contains 0.88 Mb. The plasmid is approximately 0.09 Mb. Chromosome 3 has also been characterized as a large plasmid, or megaplasmid (pC3); unlike chromosomes 2 and 3, it does not contain essential housekeeping genes, instead coding for accessory functions such as virulence and resistance to stress.

Motility
Burkholderia cenocepacia has the ability to swim and swarm inside the body. It has a polar flagella, and produces a surfactant. These characteristics are necessary for the species to have motility in an agar medium. The surfactant produced by Burkholderia cenocepacia allows other pathogenic bacteria in the lungs to have motility. This means that the presence of Burkolderia cenocepacia is necessary for swarms of bacteria to coexist and cooperate in the lungs.

Quorum Sensing
One kind of cell-to-cell communication employed by B. cenocepacia is quorum sensing, which is the detection of fluctuations in cell density and usage of this information to regulate functions such as the formation of biofilms and siderophore production. Like other Gram negative bacteria, B. cenocepacia produces acyl-homoserine lactones (AHLs), signaling molecules that in members of the Burkholderia cepacia complex specifically are encoded by two systems--the CepIR system, which is highly conserved in the Bcc, and the CcIR system. The two AHL-mediated QS systems, CepIR and CciIR, regulate each other; the CepR protein is required for the transcription of the cciIR operon, while the CciR protein represses transcription of cepI. The CciIR system can also negatively regulate the CepIR system through the production of C6-HSL, a type of AHL produced primarily by CciI proteins that inhibits the activity of CepR proteins. B. cenocepacia also uses cis-2-dodecenoic acid signals, which are known as Burkholderia diffusible signal factors (BDSF) because Burkholderia cenocepacia is where they were first discovered.

Environments
Burkholderia cenocepacia has been found to thrive in microaerophilic conditions, which consist of little to no oxygen. Experimental studies conducted on the growth of B. cenocepacia in environments akin to the human lungs demonstrated the pathogen's increased success in microaerophilic environments over aerophilic settings.

In environments with little available iron such as the lungs of a cystic fibrosis patient, Burkholderia cenocepacia secretes siderophores, molecules that bind to iron and transport them to the bacteria. Of the four types of siderophores produced by the Bcc, B. cenocepacia produces three: ornibactin, pyochelin, and salicylic acid (SA). Ornibactin is the most important iron uptake system and can sustain the bacteria in an iron-deficient environment even without the production of functioning pyochelin or SA.

B. cenocepacia has been demonstrated to colonize an array of ecological niches with diverse lifestyles. The ability to utilize a wide range of carbon sources accompanies the ability of Bcc species to be efficient with plant-growth promotion, bioremediation, and biocontrol. High potential of Bcc species, including B. cenocepacia, as a biocontrol of plant-growth promoting agents has been demonstrated; however, the mechanisms that support this are not known. In a bioremediation context, B. cenocepacia demonstrated phytopathogenic properties in causing fingertip rot in bananas.

Pathogenicity
Burkholderia cenocepacia is an opportunistic pathogen that commonly infects immunocompromised patients, especially those with cystic fibrosis, and is often lethal. In cystic fibrosis, it can cause "cepacia syndrome," which is characterized by a rapidly progressive fever, uncontrolled bronchopneumonia, weight loss, and in some cases, death. A review of B. cenocepacia in respiratory infections of cystic fibrosis patients stated that "one of the most threatening pathogens in [cystic fibrosis] is Burkholderia cenocepacia, a member of a bacterial group collectively referred to as the Burkholderia cepacia complex (Bcc)." Twenty-four Small RNAs were identified using RNA binding properties of the Hfq protein during the exponential growth phases. sRNAs identified in Burkholderia cenocepacia KC-0 were upregulated under iron depletion and oxidate stress. In Seattle, a team led by microbiologist Joseph Mougous at the University of Washington had discovered a strange enzyme (a toxin called DddA) made by the bacterium Burkholderia cenocepacia — and when it encountered the DNA base C, it converted it to a U. Because U, which is not commonly found in DNA, behaves like a T, the enzymes that replicate the cell’s DNA copy it as a T, effectively converting a C in the genome sequence to a T. This has reportedly been used for the first gene-editing of mitochondria – for which a team at the Broad Institute developed a new kind of CRISPR-free base editor, called DdCBE, using the toxin.

The complex assembled by the bacterium (BCC) is present in all living things from plants to animals. In humans, it causes bloodstream infections. There are predisposing factors to the formation of this complex, such as the use of steroids, immunosupressive drugs, chemotherapy, central lines, use of higher antibiotics, and diabetes mellitus type 2. Patients with low immunity are at risk for the pathogen, while it is not considered a risk in healthy people. The infection is more common in male patients.

Drug resistance

Structural factors that contribute to the drug resistence of B. cepacia include: an impermeable outer membrane, an efflux pump mechanism, and the production of a beta-lactamase. They can also survive with minimal nutrients.

Challenge infection prevention as they are resistant to some disinfectants and antiseptics, and can survive on surfaces, including human skin and mucosal surfaces for an extended period of time.

Treatments

Isolating of the species in the complex showed 64% B. cepacia and 30% B. cenocepacia makeup.

All of the extracted isolates are sensitive to antibiotic minocycline.

Outbreaks

Contamination in health care settings

Role in disease
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Cystic fibrosis
Burkholderia cenocepacia is one of the seventeen dominant bacteria attributed with cystic fibrosis. Most notably, B. cenocepacia has such high transmissibility that it has spread across continents, most notably Europe and Canada, between cystic fibrosis patients at epidemic levels. Patients with cystic fibrosis are threatened most by opportunistic pathogens; in this case, B. cenocepacia is a member of the Burkholderia cepacia complex (Bcc). Based on the distribution of Bcc species in sample cystic fibrosis patient populations, B. cenocepacia claims between 45.6% and 91.8% of all infections caused by the Bcc complex. Compared to other infectious agents found in cystic fibrosis patients, the Bcc complex demonstrates the greatest association with increased morbidity and mortality. Among the seventeen bacteria that comprise the Bcc complex, B. cenocepacia was shown to possibly accelerate BMI decline and FEV1 (forced expiration) at the greatest rate, leading to worse prognoses for cystic fibrosis patients.

Secretion systems
Burkholderia cenocepacia utilizes a Type VI secretion system.

Biotechnology
Given the opportunistic nature of the Bcc complex and B. cenocepacia, the severity of respiratory infections is too intense for applications in biotechnology to be allowed. (https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1462-2920.2010.02343.x)

Agriculture
To increase soil health, plant-growth promoting rhizobacteria (PGPR) are used in the agricultural industry to create bio-organic fertilizers. A current challenge is identifying which bacterial species are optimal at stimulating plant growth in bio-organic fertilizers. Creating bio-organic fertilizers has been increasingly successful with the use of plant-growth promoting rhizobacteria mixed with organic substrates. B. cenocepacia has various PGPR traits like phosphate solubilization that make it well-suited to promote growth. With the addition of solid-state fermentation technology, creating bio-organic fertilizers was highly successful by incorporating B. cenocepacia with high protein content agricultural wastes.