Mycoplasma is a genus of small
bacteria which lack
cell walls. Several species are
pathogenic in humans, including
M. pneumoniae[?], which is an important cause of
pneumonia and other respiratory disorders, and
M. genitalium, which is involved in pelvic inflammatory diseases. An analysis of
tRNA and
rRNA sequences indicates that
Mycoplasma belongs among the
Firmicutes, and in particular is derived from the
Lactobacillus-
Clostridium[?] group by losing a significant amount of DNA.