Streptomyces avermitilis: Difference between revisions
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==Genome structure== | ==Genome structure== | ||
The chromosomes of ''Streptomyces avermitilis'' form 9.02-Mb linear structures -- one of the largest bacterial genome sequences yet. It also has a higher GC content (70.7%) than almost all other organisms, making the ''S. avermitilis'' chromosome unique in its size and structure (3). The linear chromosome contains 7,574 open reading frames (ORFs) and unique terminal-inverted repeats at both ends that bind terminal proteins. Of the 7,574 ORFs, 4,563 (or 60.2%) encode funtional proteins and about 35% (or 2,663) cluster into 721 paralogous families. Two main gene families are represented -- one relating to membrane-spanning components of ABC transporters, and the other relating to two-component transcriptional regulator systems. These results suggests that at least a third of all ''S. avermitilis'' genes may have emerged as a result of gene duplication during evolution (4). | |||
Comparing the genomes of ''S. avermitilis'' and ''S. coelicolor'' A3(2) revealed a 6.5-Mb highly conserved internal region where all known essential genes are located (SAV1625-7142 in ''S. avermitilis''). This region is structurally similar to other circular bacterial chromosomes, implying that this 6.5-Mb internal region may be the underlying backbone of the ''Streptomyces'' chromosomes and may have evolved from an ancestor common to all bacteria with circular chromosomes. Conversely, there are variable and less conserved regions found near both telomeres. More than half the genes related to secondary metabolism were found in subtelomeric regions, while no known essential genes were found there (4). | |||
''S. avermitilis'' also contains the plasmid SAP1. SAP1 has 96 ORFs, 33 (or 34.4%) of which encode funtional proteins (4). | |||
Overall, the gene content of ''S. avermitilis'' suggests that its genome may have evolved by the acquisition of novel gene functions that helped it to adapt to the intense competition, the fluctuation of nutrient availability, and the extremely variable physical conditions of soil environments (4). | |||
==Cell structure and metabolism== | ==Cell structure and metabolism== | ||
Revision as of 15:44, 29 August 2007
A Microbial Biorealm page on the genus Streptomyces avermitilis
Classification
Bacteria; Actinobacteria; Actinobacteridae; Actinomycetales; Streptomycineae; Streptomycetaceae; Streptomyces; Streptomyces avermitilis
Species
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NCBI: Taxonomy |
Streptomyces avermitilis
Description and significance
Streptomyces avermitilis was first isolated in 1979 at Kitasato Institute from a soil sample collected at Kawana, Ito City, Shizuoka Prefecture, Japan. It was sent to Merck Sharp & Dohme Research Laboratories for screen testing. (1)
This particular Streptomyces species dwells in terrestrial soils and has a brownish-gray spore mass. The spores are spherical (as opposed to oval) with a smooth spore surface and come in chains of more than 15. The sporophores form spiral side branches on aerial mycelia. (1)
S. avermitilis is an important species to have its genome sequenced because it produces certain secondary metabolites, called avermectins, that have antihelmintic and insecticidal properties. (2)
Genome structure
The chromosomes of Streptomyces avermitilis form 9.02-Mb linear structures -- one of the largest bacterial genome sequences yet. It also has a higher GC content (70.7%) than almost all other organisms, making the S. avermitilis chromosome unique in its size and structure (3). The linear chromosome contains 7,574 open reading frames (ORFs) and unique terminal-inverted repeats at both ends that bind terminal proteins. Of the 7,574 ORFs, 4,563 (or 60.2%) encode funtional proteins and about 35% (or 2,663) cluster into 721 paralogous families. Two main gene families are represented -- one relating to membrane-spanning components of ABC transporters, and the other relating to two-component transcriptional regulator systems. These results suggests that at least a third of all S. avermitilis genes may have emerged as a result of gene duplication during evolution (4).
Comparing the genomes of S. avermitilis and S. coelicolor A3(2) revealed a 6.5-Mb highly conserved internal region where all known essential genes are located (SAV1625-7142 in S. avermitilis). This region is structurally similar to other circular bacterial chromosomes, implying that this 6.5-Mb internal region may be the underlying backbone of the Streptomyces chromosomes and may have evolved from an ancestor common to all bacteria with circular chromosomes. Conversely, there are variable and less conserved regions found near both telomeres. More than half the genes related to secondary metabolism were found in subtelomeric regions, while no known essential genes were found there (4).
S. avermitilis also contains the plasmid SAP1. SAP1 has 96 ORFs, 33 (or 34.4%) of which encode funtional proteins (4).
Overall, the gene content of S. avermitilis suggests that its genome may have evolved by the acquisition of novel gene functions that helped it to adapt to the intense competition, the fluctuation of nutrient availability, and the extremely variable physical conditions of soil environments (4).
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
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 Jennifer Woods, student of Rachel Larsen
