Streptomyces lividans
A Microbial Biorealm page on the genus Streptomyces lividans
Classification
Domain: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Subclass: Actinobacteridae
Order: Actinomycetales
Suborder: Streptomycineae
Family: Streptomycetaceae
Strains: Streptomyces lividans
Species
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NCBI: Taxonomy |
Genus species: Streptomyces lividans
Description and significance
Streptomyces lividans is a gram-positive, filamentous, soil bacterium. With its high G-C content, this species is known for its genomic plasticity, which consists of large deltions and extensive amplifications (1). Responsible for the breakdown of organic soil material, Streptomyces are non-pathogenic bacteria that live in colonies. Because of their natural habitat, along with the non-pathogenic character of the species in the genus, S. lividans is used as hosts for the synthesis and secretion of homologous and heterologous proteins (3). Bacteria belonging to the genus Streptomyces have mycelial growth, undergoing a complex biochemical and morphological change before forming exospore chains (2). In short, the complex life cycle of the genus comprises of the germination of spores to form a branched, vegetative mycelium, which then produces an aerial mycelium, and finally, spores (1). The Streptomyces lividans has been extensively studied in laboratories for possible therapeutic uses because of its abundance in multi-drug resistant genes. The Streptomyces genus is responsible for producing a majority of the antibiotics, some immunosuppressants, and anti-tumor agents used today (9).
Genome structure
Streptomyces lividans has a linear structure, and compared to streptomyces coelicolor, they have common structures with identical ordering of the cosmid sequence (1). The central core region contains the essential genes, while the arms carry conditionally adaptive genes and species-specific DNA (13). Present in multiple copies in the vegetative and aerial mycelium, the chromosome is apparent only as a single copy in the spores. Physical map of the s. lividans genome was done by using restriction endonucleases AseI and DraI, cutting the linear chromosome into 16 and 7 fragments, respectively. The 8000 kb or so linear genome has an approximate 70% G+C content (1). Unlike most eubacteria, Streptomyces species usually contain linear chromosomes and plasmids. The linear plasmids are 12-1700 kb long. With inverted repeat sequences in their telomeres, replication of Streptomyces linear plasmids starts at centrally located loci and continues bidirectionally towards the telomeres. This leaves a single strand overhand of approximately 280 nt. as an intermediate. However, when the telomeres are deleted, the centrally located loci of Streptomyces linear plasmids can also maintain the circular mode. The replication modes and functions of different Streptomyces species has been highly conserved (7).
While replication modes remain conserved within the Streptomyces genus, there are considerable phenotypic variations observed across many genera of actinomycetes. Because of the high frequency of deletions, insertions, amplifications, and rearrangements, there are high levels of chromosomal instability. Also, horizontal gene transfer account for further genome instability of the genome (10).
Cell structure and metabolism
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Ecology
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Pathology
Streptomyces are non-pathogenic so it does not cause disease in animals, plants, and humans, although some species are plan pathogens. For example, Streptomyces scabies causes potato scabs and Streptomyces ipomoeae causes disease in sweet potatoes (14, 15).
Application to Biotechnology
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Current Research
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References
Edited by Linnea Shen, student of Rachel Larsen
