Acholeplasma axanthum, sp. n.: a New Sterol-Nonrequiring Member of the Mycoplasmatales

Abstract

Mycoplasmas recovered from tissue cultures and previously shown to belong to the sterol-nonrequiring group of mycoplasmas have been further characterized. The biological and serological properties of these strains show them to be clearly distinct from Acholeplasma laidlawii and A. granularum , two species of sterol-nonrequiring mycoplasmas recently reclassified. It is proposed that the newly described mycoplasmas be designated Acholeplasma axanthum , sp. n.

Existence of carotenoids in Acholeplasma axanthum

“…The incontrovertible finding of carotenoid pigments in A. axanthum appears to be in direct contradiction to previous reports (12,13). The organism used in this study was proven to be A. axanthum both by its serological identity with known specific antiserum and by the presence of sphingolipids specific to this Acholeplasma species.…”

“…This color was extractable with chloroform-methanol and appeared in the neutral lipids upon further fractionation. The spectral characteristics of this crude fraction suggested the existence of carotenoid pigments, despite previous reports (12,13) of the absence of such absorption and the minimal incorporation of ["C]acetate into the neutral lipid fraction. Because ['4C]acetate is greatly diluted in the crude culture medium, [2-'4C]mevalonic acid (dibenzylethylamine diamine salt) was chosen as a better precursor for demonstration of carotenoid biosynthesis.…”

“…of the genus Acholeplasma reported devoid of carotenoid pigments, even though it does not require sterols for growth (12,13). The absence of carotenoids has been concluded from the lack of appreciable absorption at 438 nm by lipid extracts of small cellular pellets and the minimal incorporation of ["4C]acetate into the nonpolar lipid fraction (12).…”

Mycoplasmas and cell cultures.

“…More recently, mycoplasmas of presumed avian (42,75), swine (24, 61, 75), and murine (47) origin have been isolated. The saprophytic strain M. laidlawii (75), now reclassified as Acholeplasma laidlawii because of its nonrequirement for sterols for growth, and other sterol nonrequirers such as A. granularum (196) and as yet unclassified species (197,198) are becoming increasingly common cell-culture contaminants. The nonhuman origin of these mycoplasmas raises questions as to the source of these contaminants, although the degree of host specificity of mycoplasmas is itself in question since swine mycoplasmas (75) and A. laidlawii (75,110,149) have been isolated directly from human clinical material.…”

“…There has already been one report of two distinct species infecting the same cell culture (78). As mentioned previously, many serologically different strains of mycoplasma are now being isolated from tissue cultures, including species as yet unclassified (197,198). Multivalent antisera would be required to eliminate such contaminants.…”