Candida albicans

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Description and significance

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Microscopic image of Candida Albicans.

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Candida albicans is able to sexually reproduce and is a diploid fungus. It is a common occupant of the human intestine. It is often associated with yeast related diseases in the genitals and in the mouth of animals. It is one of the most common pathogens found in humans and is the source of a variety of different infections. Like most microorganisms found in the digestive tract of animals, C. albicans falls into a class of relationships that occur between organisms where one benefits and the other is not significantly harmed or benefited. C. albicans can be found in most of the general population causing no detrimental side effects. Although it is not found to be harmful, an overgrowth of C. albicans, known as candidasis, is harmful to the individual. Individuals with a healthy immune system are able to fight off the disease, however in HIV patients with weakened immune systems; it is much more difficult for the disease to be fought off and can lead to more serious problems. In order for the disease to be transmitted to the host, the yeast form of C. albicans responds to changes in the environment, becomes harmful, and changes from a unicellular form into a multicellular.

Genome

C. albicans was one of the first eukaryotic pathogens chosen for gene sequencing. The genome of Candida albicans was sequenced due to the fact that it is one of the most common human fungal pathogen. Most isolates of C. albicans used for genetic analysis are mostly diploid and some even contain translocations in their genes. Unlike most species that undergo sequencing, a haploid form of C. albicans is unavailable. Due to its extensive use in molecular analyses and virulence in animal models, SC5314(7) was selected for large- scale sequencing. C. albicans was first sequenced at the Stanford DNA Sequencing and Technology Center. The diploid sequence assembly displayed the amount of heterozygosity in the strain SC5314. The results obtained from this along with results from the sequencing afforded many important discoveries in C. albicans development.To put together the C. albicans diploid genome sequence, a commonly used assembly program called the “phrap” was used. Using the phrap, resulted in an assembly in which the products of the overlapping DNA fragments (contigs), were as much as 20% much greater than the size of the haploid genome.The ultimate diploid sequence was disperesed over 412 supercontigs, 146 homologous pairs, 119 phrap contigs, and one supercontig produced from two phrap contigs joined on the basis of GenBank sequence.The genome sequence shows many adaptations that are needed for environmental responding and sensing. Due to the fact that C. albicans is able to pass through the digestive tract, it requires it to be able to deal with extreme variations of pH. A number of genes associated with pH regulatory have been found in C. albicans.

Heterozygosity

The heterozygosity (the genetic variation in a population) of the Candida genome surpasses most microbes in other genomes and is commonly found in clinical isolates. The diploid assembly clearly shows the extent amount of heterozygosity in C. albicans. The entire population of C. albicans is said to have high polymorphisms. The average frequency of polymorphism is one in 237 bases. Many allelic differences have been found in C. albicans but their significance is not known. It is thought that these differences may increase genetic diversity and add to the development of drug resistance.

The polymorphisms found in C. albicans are distributed unevenly across its genome. Dissimilar single base polymorphisms yield two proteins that have differences in one or many amino acids that may give functional differences for each protein. This circumstance increases the amount of different types of proteins determined by the genome.

Current research

"Candida albicans and inflammatory bowel disease"

It has been recently discovered that Candida albicans syndrome impinges upon one third of the U.S. population. The illness takes its form in many variations affecting the lymphatic, digestive, reproductive, and urinary systems. The fungus known as Candida albicans can be seen in most healthy individuals, however when an immune system can not protect itself fully, this bacteria multiplies and rapidly overproduces itself. This overproduction release toxins that are then absorbed into the bloodstream, and can cause and individual to get a variety of unpleasant ailments. It has recently been discovered that AIDS patients and cancer patients with this “ailment” have many complications due to their weakened immune system and their inability to fight it off. An additional complication Candidas albicans raises is infertility in males and females.The yeast colonies formed survive by consuming dead tissue. It only becomes a health threat when something impacts the growth and overproduction of the colonies. This can occur for many reasons such as, antibiotics, birth control pills, and artificial hormones. When these are introduced, other bacteria are “killed off” in turn giving more room for the yeast colonies to grow. The overgrowth of Candida can become visible in many different ways such as, allergic reactions, and gastrointestinal and urinary tract disorders. Given that Candida albicans can be found over must of the body even in healthy individuals, testing for it in a laboratory will not help much. The way to measure if it is malignant or not is to test the amount of antigens found in an individuals blood serum which in turn corresponds to the amount of yeast.

"Candida Albicans Genome Fully Annotated: The National Research Council of Canada heads an international team, bringing new hope to people with immune system deficiencies"

The National Research Council Biotechnology Research Institute announced the publication of an article that discloses the complete genomic explanation of Candida albicans. C. Albicans is a fungal pathogen and is one of the most common causes of infection in people that are immunocompromised, and is currently becoming more complicated to treat. It is a single cell fungus exists naturally in normal human bacterial contents. Around 30 to 40% of serious fungal infections that are mostly attributable to C. Albicans, result in death. Individuals most vulnerable to this yeast are premature infants, transplant recipients taking immunosuppressive drugs, HIV positive patients, and cancer patients. Candida is the fourth leading source of infection in current hospitals. The treatments currently given are only effective to an extent due to the microorganism’s resistance to antibiotics. The complete and accurate annotation of Candidas genome, will aid researchers in better understanding the pathogens weaknesses and improve existing therapeutic agents. Based on C. albicans annotations, researchers have been able to produce the first non- commercial microarray that can be used by researchers globally to study the genomic and polemics of Candida. The microarray of Candida is made up of an arrangement of around 600 DNA samples on a single glass slide. There are others that differ in size and are used to examine entire genomes. They are able to concurrently evaluate the expression and interactions of an organism’s gene, which is an important factor in developing more effective medical treatments.

Pathology

An infectious disease can be produced by the fungus Candida albicans. The yeast Candida albicans is a common occupant of the human mouth, throat, and reproductive organs. This fungus does not cause harm or disease when in ecological balance with other microbes, however, many factors can cause C. albicans to grow rapidly so that it can not be controlled by the body’s defense systems, resulting in a thrush. A thrush is a yeast infection characterized by whit spots, usually on the tongue or inner cheeks, followed by and ulcer. In order to “survive” a thrush needs a weakened host and favorable conditions. It frequently causes no ill side effects except among infants and in AIDS patients due to their their weakened immune systems. It has been discovered that the use of many types of antibiotics may make it easier for candiasis to develop by killing off normal microbes that usually fight off the fungus. Candidiasis of the skin is mostly found in moist areas and folds. There have been cases where the fungus has invaded the respiratory system producing a bronchopulmonary infection, which can lead to damaging of the heart. While some forms of candidiasis are easily curable, others are more unmanageable. Some treatments that have helped individuals suffering from candidiasis are iodide and nystatin (an antifungal antibiotic).

References

[1]↑Chibana, H., Magee, B. B., Grindle, S., Ran, Y., Scherer, S. & Magee, P. T. (1998) Genetics 149 , 1739-1752.

[2]↑Jones T, Federspiel NA, Chibana H, et al (May 2004). "The diploid genome sequence of Candida albicans". Proceedings of the National Academy of Sciences 101 (19): 7329–34.

[3]↑"Candidas Albicans." Wikipedia, The Free Encyclopedia. 2 Apr 2009, 08:50 UTC. 4 Apr 2009 <http://en.wikipedia.org/w/index.php?title=Actimel&oldid=281256710>.