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(New page: Description and significance Candida albican,sometimes known as Monilia, is a form of yeast, a single-celled, diploid fungus that is capable of mating sexually but not meiosis It feeds fro...)
 
 
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Description and significance Candida albican,sometimes known as Monilia, is a form of yeast, a single-celled, diploid fungus that is capable of mating sexually but not meiosis It feeds from sugar. Also, Carbohydrates and alcohols when they break down into sugar. They are six common species of yeast that are living in human’s body and C. albicans are the most common one. It exists as a commensal of warm-blooded animals. Candida albicans prefer moist and dark environments, which has a pH of 4.0 to 5.0.They forms benign colonies which they grow on the moist surfaces of the body. When the helpful bacteria which “graze” upon them are absent, the situation is very good for the colony of C. albicans to grow rapidly.(1) The believe on C. albicans having no sexual cycle was just changed recently.In 1999 Hull and Johnson demonstrate that C. albicans strain CA14 contained MTLa1 ono ne chromosome and MTLalpha1 and MTLalpha2 on the homologous chromosome.After that, fusion happened between those two strains(2) Microscopic morphology of C. albicans plated on cornmeal following 72 hours incubation at 25°C, it presents abundant branched pseudohyphae and true hyphae with blastoconidia. The blastoconidia are formed in grape-like clusters along the length of the hyphae. Terminal chlamydoconidia may be formed with extended incubation. Candida albicans switch between different morphologies is required for pathogenesis. [edit] Genome structure Candida albicans has the special ability to form thick-walled cells, termed chlamydospores, in certain environmental conditions. Human fungal pathogen C. albicans is capable of going through the morphological transition from unicellular to multicellular hyphal growth.Cell is going through assymetric division,whike having the hyphal growth.The apical cell divids while the subappical cell remains in G1 and cell surface growth is highly restricted to the tip of the apical cell.(3) The genome of C.albicans is very plastic and has variable karyotype.Strain SC5314 is made of 8 chromosome pairs and from those,7 have a constant size and one of which is polymorphic(R)and its size ranges from 3.2 to 4.0Mb.The existance of array genes for rRNAs is responsible for the size variation. The gene size of this strain is around 16Mb. One of the most interesting features of C. albicans genome is the accurnace of neumeric and structural chromosomal rearrangements as means of generating genetic diversity,named chromosome length polymorphism,reciprocal translocations, chromosome deletion and trisomy of individual chromosome. These all lead to changes in the phenotype, which is simply an adaptation to an environment. The C. albicans genome for strain SC5314 was sequenced at the Stanford University. The genome of the WO1 strain was also sequenced(Broad Institude of MIT and Harvard) The Genome sequencing effort was was launched in October1996.The sequencing the genome of C. albicans changed the way that C. albicans are understood now. The fact that C. albicans have very dynamic genomes,is a benefit for studying them and their population studies. One important discovery from their genome sequence was finding the parasexual cycle in C. albicans. This cycle is being control by mating-typ eloci and its phenotype changes between white and opaque. The role that mating process plays in dynamics of C. albicans provide an essential focus for the future research.(4) [edit] Cell structure and metabolism The cell wall is essential to nearly every aspect of the biology and pathogenicity of Candida albicans.(6) Lots of new studies are showing that it is a dynamic organelle.The major components of the cell wall are glucan and chitin, which are associated with structural rigidity, and mannoproteins.Wall proteins might differ in their secretion, or topological location within the wall structure.Expression of some proteins is associated with the morphological growth form of the fungus and may play a role in morphogenesis.Surface mannoproteins are strong immunogens that trigger and modulate the host immune response during candidiasis. Metabolism: Candida albicans contains two APSES proteins:the regulator Efg1p and its homologue Efh1p.Overexpression of both of these two will result in the similar phenotype(the white to opaque switching as we mentioned before). The result of deleting efh1 was no phenotype under normal condition. On the other hand,it casued hyperfilamentation under hypoxic conditions. Efg1p not only regulates genes involved in morphogenesis but also strongly influences the expression of metabolic genes, inducing glycolytic genes and repressing genes essential for oxidative metabolism.The result of the experiments show that Efh1p is an activator of gene expression.Also the same experiment supports that Efh1p supports the regulatory functions of the primary regulator, Efg1p, and indicate a dual role for these APSES proteins in the regulation of fungal morphogenesis and metabolism. [edit] Ecology C. albicans have a preference to live in moist,dark and warm enviornment, with a pH of 4.0 to 5.0(acidic)They are one of the gut flora(living in gastroontestinal tract). they also live in human mouth and under normal condition, they live in 80% of human population with no harmful effect.They also appear on mocus and vagina membrane.They can also appear in blood and genital tract.In some cases they have symbiotic relationship with their host and in some other, they wont(More detail in Pathology) (4) There are some major intercatons that C. albicans are involved in.They have done a study of Cellular and Molecular biology of C. albicans Estrogen response(5)During the experiment,exposure to estrogens did not significantly change the biomass of any C. albicans culture tested.The cell bio and gene expression from this study lead to a model that proposes how components of the phospholipid and sterol metabolic pathways may interact to affect C. albicans germ tube formation and length. [edit] Pathology C. albicans are responsible for different infections.Infections caused by Candida species have substantially increased in incidence over the past 2 decades.(7) Researchs show that Candida albicans is the most common etiological agent of vaginal candidiasis.As in vaginal candidiasis or thrush, the main symptom of which is intense itching. When the balance between bacteria and yeast is upset,small colonies of candida can caused yeast infection in humans.General term for an infection is candidiasis,but it may vary depends on the type of infection and also region of the body. It is estimated that more than half of women and men host C. albicans and also around 75% of women will have an episode of vulvo-vaginal candidiases at least once in theier life. Infants can also be a victim of C. albicans.They may develope yeast infection as an adjusting to diaper rash.(1) Also there are nail infections in humans caused by Candida albicans.To cure that infection, they were using Terbinafine(this drug is active in response to some pathogenic fungi such as molds,dimorphic fungi, and some yeasts)but studies show that drug had little activity against Candida albicans.(8) Mucocutaneous candidiasis caused by C. albicans is a comon cause of HIV in humans.(8-1) Most common symptons of disease casued by C. albicans are: -gastrointestinal and urinary tract disorders -allergic reactions -mental and emotional disturbances -endocrine system compromise [edit] Application to Biotechnology 8.1 Candida albicans Produce Immunomodulatory Prostaglandins prostaglandins belong to lipid compounds and they have an important role in animals bodies.Their main role is that they are regulators of host immune responses.(9) Both host cells and also fungal pathogens are sources of producing prostaglandins.The objective of this research was to find out if C. albicans are producing the prostaglandins or not, and if they do,find out the role these lipids play in yeast biology and also disease pathogenesis. The result of the experiment by three different independent assays C. albicans produces and also secretes prostaglandins.

8.2 High levels of hydrolytic enzymes secreted by Candida albicans isolates involved in respiratory infections In this experiment,which was done on a large panel of C. albicans(n=186),differences in production of two putative virulence factors of C. albicans,phospholipase and proteinase,were measured and studied. Result of the experiment were that the C. albicans from healthy volunteers were all showing low phospholipase activity and vice versa. Also,C. albicans from HIV positive humans,caused sever infection and they produced high amount of proteinase.(10,11) [edit] Current Research 9.1 Persistence of Candida albicans candidemia in non-neutropenic surgical patients According to clinical trial experinece,treatment failure in pateints with candidemia is high.The main focus now is on the first line treatment strategies. When there is no evident Canida albicans seeing the eye or intravascular catheter,primary treatment failiure with fluconzole and secondary treatment with caspofungin happens.In patients with multiple risk factors,possibility of primary and secondary failure may be neglected. Extra research and controlled clinical data are needed to guide the choice of secondary antifungal treatment in those patients.(12) 9.2 Histatin 5-derived peptide with improved fungicidal properties enhances HIV-1 replication Antimicrobial peptides are found on the mocus surfaces of the body and have inhibitory activity against bacteria, fungi, parasites, and viruses.Histatin 5 is a peptide in saliva that inhibits C. albicans(a fungus that causes HIV.In previous studies,they added to fungi properties of H5 by replacing the amino acids(Dh-5) Current researches are focusing on anti-HIV activiteis of Dh-5.The study shows that modifications on peptides, in order to improve their performances against pathogens,is not neccessarily the greatest thing.It may have some side effects on other pathogens.(13) 9.3 Biochemical characterization of recombinant dihydroorotate dehydrogenase from the opportunistic pathogenic yeast Candida albicans C. albicans are becoming very resistance to antifungal agents.In this research, the work is focused on C. albicans dihydroorotate dehydrogenase (DHODH, EC 1.3.99.11), as a new target to control infection. As a result of this research,Only inhibitors of mammalian DHODH were able to reduce C. albicans DHODH activity. This study provides a background for the development of antipyrimidines with high efficacy for decreasing in situ pyrimidine nucleotide pools in C. albicans.(14) [edit] References (1) Candida albicans at NCBI Taxonomy browser, url accessed 2006-12-26 (1)Factors Affecting the Morphology of Candida Albicans" Dan Otho McClary Annals of the Missouri Botanical Garden, Vol. 39, No. 2 (May, 1952), pp. 137-164. doi:10.2307/2394509 (2)Jones T, Federspiel N, Chibana H, Dungan J, Kalman S, Magee B, Newport G, Thorstenson Y, Agabian N, Magee P, Davis R, Scherer S (2004). "The diploid genome sequence of Candida albicans". Proc Natl Acad Sci U S A 101 (19): 7329-34. PMID 15123810. (3) Odds, F C. Candida and candidiosis. London, England: Baillière Tindall; 1988. (4)Temporal and spatial control of HGC1 expression results in Hgc1 localization to the apical cells of hyphae in Candida albicans.Wang A, Lane S, Tian Z, Sharon A, Hazan I, Liu H. Department of Biological Chemistry, University of California, Irvine, CA 92697 (5)Eukaryotic Cell, January 2006, p. 180-191, Vol. 5, No. 1 1535-9778/06/$08.00+0 doi:10.1128/EC.5.1.180-191.2006 (6)Microbiol Mol Biol Rev, March 1998, p. 130-180, Vol. 62, No. 1 1092-2172/98/$04.00+0 (7)Beck-Sague´ CM, Jarvis WR, the National Nosocomial Infections Surveillance System. Secular trends in the epidemiology of nosocomial fungal infections in the United States, 1980–1990. J Infect Dis 1993;167:1247–51. (8)Antimicrobial Agents and Chemotherapy, May 1998, p. 1057-1061, Vol. 42, No. 5 0066-4804/98/$04.00+0 (8-1)Clin Infect Dis. 1993 Dec;17(6):1018-21. (9)Peters-Golden, M. Lipid mediator synthesis by lung macrophages. In: Lipscomb M F, Russell S W. , editors. Lung macrophages and dendritic cells in health and disease. Vol. 102. New York, N.Y: Marcel Dekker, Inc; 1997. pp. 151–182. (10)Price, M. F., Wilkinson, I. D. & Gentry, L. O. (1982). Plate method for detection of phospholipase activity in Candida albicans. Sabouraudia 20, 7–14.[Medline] (11)Ollert, M. W., Wende, C., Gorlich, M., McMullan-Vogel, C. G., Borg-von Zepelin, M., Vogel, C. W. & Korting, H. C. (1995). Increased expression of Candida albicans secretory proteinase, a putative virulence factor, in isolates from human immunodeficiency virus-positive patients. J Clin Microbiol 33, 2543–2549.[Abstract] (12)J Chemother. 2007 Jun;19(3):335-8. (13)J Virol. 2006 Sep;80(18):9236-43 (14)FEBS J. 2006 Jul;273(14):3183-91. Epub 2006 Jun 15 Retrieved from "http://microbewiki.kenyon.edu/index.php/Candida_albicans"