Mycobacterium avium complex: Difference between revisions
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==Cell structure and metabolism== | ==Cell structure and metabolism== | ||
Mycobacterium avium are acid fast bacillus. They are characterized by a thin cell wall covalently attached to the long chain of hydrocarbons called mycolic acid. This complex between the peptidoglycan and mycolic acids creates the waxy hydrophobic surface of the cell, which greatly restricts the transport of many compounds into and out of the cell, and eventually slows down growth. Because of its high hydrophobicity due to the waxy outer layer, many soluble antibiotic drugs cannot cross the membrane and attack the pathogen. Therefore, Mycobacterium avium are extremely resistant to many chemotherapeutic agents as well as many cleaning products, leaving only a limited number of drugs that these bacteria are fairly susceptible to. When taking drugs to treat MAC infection, it is usually accompanied by a special agent or detergent to break down the waxy layer and allowing the drug to penetrate into the cell. Mycobacteria also have a lipopolysaccharide (LPS) anchored into the plasma membrane of the cell with the carbohydrate chain sticking out of the cell (6). | |||
Little information is known about the process of biosynthesis and breakdown for this complex of organisms. What is known is that these organisms undergo aerobic respiration, requiring them to find a way to get oxygen, either through their hosts or in the environments. They use palmitic and oleic acids as their main carbon and energy source. Palmitate and oleate are long chain fatty acids that could later be incorporated into the hydrophobic surface of the cell that is characteristic of acid-fast mycobacteria. | |||
==Ecology== | ==Ecology== | ||
Revision as of 07:24, 29 August 2007
A Microbial Biorealm page on the genus Mycobacterium avium complex
Classification
Higher order taxa
Bacteria (domain); Actinobacteria (phylum); Actinobacteria (class); Actinobacteridae (subclass); Actinomycetales (order); Corynebacterineae (suborder); Mycobacteriaceae (family); Mycobacterium (genus); Mycobacterium avium complex (MAC) (species group).
Species
Includes: Mycobacterium avium
Mycobacterium intracellulare
Also known by: Mycobacterium avium intracelluare (MAI)
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NCBI: Taxonomy |
Description and significance
Mycobacterium avium complex (MAC) contains 28 serovars of two species of mycobacteria: Mycobacterium avium and Mycobacterium intracellulare. These bacterias are slow-growing and cause opportunistic infections to animals, and immunosuppressed humans. MAC is prevalent in the environment. They are found everywhere from fresh to saltwater and even in cigarette (7). This complex commonly formed biofilms in places abundant with water, food, and soil. They are notorious for being highly resistant to many antibiotics as well as disinfectant and bleach, including Chlorine (10). The biofilms were detected by the use of crystal violet staining and optic and electron microscopy (3). They are usually distinguished by a smooth, wet surface. Biofilms have many negative effects on humans. The colonies of these different bacterial cells inside our bodies protect them from being attack by our immune system. They can develop in our bodies from the surfaces of medical implants such as urinary catheter or in the cracks of our teeth to form plaque. These bacterias also exist in water and oil pipelines, which slow and even clogged the flow of fluid (6). MAC biofilms are also believed to be essential to the survival of virulent strains. Although, the impact of biofilm is clearly evident, how MAC biofilm form remains a mystery to mankind. All that is known is that its formation is dependent on the quantity of calcium, zinc (II), and magnesium(3). Regardless of the limited information, studies are being done to identify genes of M. avium that are essential in their biofilm formation, with the hope that this information will prevent the bacterial colonization of these MAC biofilms (3).
Genome structure
Mycobacterium avium was completely sequenced on 11/29/2006 at the J. Craig Venter Institute. Its entire genome consists of 5,475,491 nucleotides long, with a GC (guanine cytosine) content of 68% and 32% for AT (adenine thymine). Guanine and cytosine are paired with each other by three hydrogen bonds, whereas adenine and thymine have 2 hydrogen bonds that bring them together. Because of the larger number of hydrogen bonds, guanine and cytosine are pulled stronger together, and it would take more energy and a higher melting temperature to separate the two. To determine the DNA genome within a cell, scientists use restriction endonuclease to cleave DNA into many small fragments. The endonucleases usually cleave at an AT rich, because two hydrogen bonds are weaker and require less energy to pull apart than three bonds. In the Mycobacterium avium, approximately 88% of its genome are coding regions for 5120 proteins. Commonly found in MAC are extrachromosomal DNA in the form of self-replicating plasmids. Studies are being done to determine the significance of plasmids in a M. avium strain (6).
Cell structure and metabolism
Mycobacterium avium are acid fast bacillus. They are characterized by a thin cell wall covalently attached to the long chain of hydrocarbons called mycolic acid. This complex between the peptidoglycan and mycolic acids creates the waxy hydrophobic surface of the cell, which greatly restricts the transport of many compounds into and out of the cell, and eventually slows down growth. Because of its high hydrophobicity due to the waxy outer layer, many soluble antibiotic drugs cannot cross the membrane and attack the pathogen. Therefore, Mycobacterium avium are extremely resistant to many chemotherapeutic agents as well as many cleaning products, leaving only a limited number of drugs that these bacteria are fairly susceptible to. When taking drugs to treat MAC infection, it is usually accompanied by a special agent or detergent to break down the waxy layer and allowing the drug to penetrate into the cell. Mycobacteria also have a lipopolysaccharide (LPS) anchored into the plasma membrane of the cell with the carbohydrate chain sticking out of the cell (6).
Little information is known about the process of biosynthesis and breakdown for this complex of organisms. What is known is that these organisms undergo aerobic respiration, requiring them to find a way to get oxygen, either through their hosts or in the environments. They use palmitic and oleic acids as their main carbon and energy source. Palmitate and oleate are long chain fatty acids that could later be incorporated into the hydrophobic surface of the cell that is characteristic of acid-fast mycobacteria.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
Edited by student of Rachel Larsen
