SCC''mec'', or staphylococcal cassette chromosome ''mec'', is a

mobile genetic element Mobile genetic elements (MGEs) sometimes called selfish genetic elements are a type of genetic material that can move around within a genome, or that can be transferred from one species or replicon to another. MGEs are found in all organisms. In h ...

of ''

Staphylococcus ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical ( cocci), and form in grape-like clusters. ''Staphylococcus'' species are facultat ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

l species. This genetic sequence includes the ''mecA'' gene coding for resistance to the

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...

methicillin Methicillin ( USAN), also known as meticillin (INN), is a narrow-spectrum β-lactam antibiotic of the penicillin class. Methicillin was discovered in 1960. Medical uses Compared to other penicillins that face antimicrobial resistance du ...

and is the only known way for ''Staphylococcus'' strains to spread the gene in the wild by

horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring ( reproduction). ...

Classification

Not all SCC''mec'' elements are identical (in fact, SCC elements without the ''mecA'' gene do exist.) SCC''mec'' elements have been classified into twelve types (I through XII) on the basis of two specific regions of their nucleotide sequences. One region is the ''mec'' complex including the ''mecA'' gene. The other is the ''ccr'' gene complex including genes coding for

recombinase Recombinases are genetic recombination enzymes. Site specific recombinases DNA recombinases are widely used in multicellular organisms to manipulate the structure of genomes, and to control gene expression. These enzymes, derived from bacteria ( ...

s. The ''mec'' complex is divided further into five types (I through V) based on the arrangement of regulatory genetic features such as ''mecR1'', an

inducer In molecular biology, an inducer is a molecule that regulates gene expression. An inducer functions in two ways; namely: *By disabling repressors. The gene is expressed because an inducer binds to the repressor. The binding of the inducer to the r ...

Distribution

The SCC''mec'' found in methicillin-resistant ''Staphylococcus aureus'' likely originated in

coagulase Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of '' Staphylococcus'' isolates. Importantly, '' S. aureu ...

-negative staphylococcal species and was acquired by ''S. aureus''. Staphylococcal strains isolated from pig farms were found to carry several different types of SCC''mec'', suggesting that they may serve as a reservoir of these elements.

References

Molecular biology Mobile genetic elements {{genetics-stub

Classification

Distribution

See also

References