Streptococcus mitis

Streptococcus mitis, previously known as Streptococcus mitior, is a mesophilic alpha-hemolytic species of Streptococcus that inhabits the human mouth. It is most commonly found in the throat, nasopharynx, and mouth. It is a Gram-positive coccus, facultative anaerobe and catalase negative. It can cause infective endocarditis. It has been widely reported that this organism survived for over two years on the Surveyor 3 probe on the moon; but some NASA scientists suggest this may be a result of contamination during or after return of Surveyor parts to Earth. S. mitis is competent for natural genetic transformation. Thus S. mitis cells are able to take up exogenous DNA and incorporate exogenous sequence information into their genome by homologous recombination. These bacteria can employ a predatory fratricidal mechanism for active acquisition of homologous DNA.