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The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates (hence the name "viridans", from Latin "vĭrĭdis", green), although some species in this group are actually γ-hemolytic, meaning they produce no change on blood agar. [1]
However, many streptococcal species are not pathogenic, and form part of the commensal human microbiota of the mouth, skin, intestine, and upper respiratory tract. Streptococci are also a necessary ingredient in producing Emmentaler ("Swiss") cheese. [9] Species of streptococci are classified based on their hemolytic properties. [10]
Streptococcus pneumoniae and a group of oral streptococci (Streptococcus viridans or viridans streptococci) display alpha-hemolysis. This is sometimes called green hemolysis because of the color change in the agar. Other synonymous terms are incomplete hemolysis and partial hemolysis.
Streptococcus vestibularis is a species of Streptococcus. [1] Streptococcus vestibularis, member of the viridans streptococci was first isolated from vestibular mucosa of human oral cavities, was described as a new species in 1988. It is noted that “Streptococcus vestibularis is a normal inhabitant of vestibules of the human oral cavity ...
The group is named after a principal member species, Streptococcus anginosus. The older name Streptococcus milleri (as well as Streptococcus milleri group, SMG) is now pseudotaxonomic, as the idea that these streptococci constituted a single species was incorrect. The anginosus group streptococci are members of the viridans streptococci group. [1]
The GC content of the S. sanguinis genome is 43.4% (higher than the GC contents of other streptococci). The genome encodes 2,274 predicted proteins , 61 tRNAs , and four rRNA operons . About 22% of the open reading frames are conserved hypothetical proteins (present in multiple species but having unknown functions), and approximately 645 of the ...
The system, created by Rebecca Lancefield, was historically used to organize the various members of the family Streptococcaceae, which includes the genera Lactococcus and Streptococcus, but now is largely superfluous due to explosive growth in the number of streptococcal species identified since the 1970s. [2]
That is the main reason it is now used in bacteriology for the differentiation of Streptococcus pneumoniae, which is optochin-sensitive, from the other, resistant alpha-hemolytic streptococci, sometimes called the viridans streptococci because of the green colouration on blood agar around colonies.