Acholeplasma seiffertii sp. nov., a Mollicute from Plant Surfaces

Abstract

Two mollicutes (strains F7T [T = type strain] and F28) isolated from floral surfaces of plants growing in Morocco and France were capable of sustained growth in serum-free (or cholesterol-free) mycoplasma broth media. The two isolates were found to be genomically and serologically related. Morphologic examination of the organisms by electron and dark-field microscopic techniques showed that each strain consists of small, nonhelical, nonmotile, pleomorphic coccoid cells surrounded by a single cytoplasmic membrane. No evidence of cell walls was observed. Growth in serum-free or cholesterol-free medium was sustained only when the medium contained a Tween 80 fatty acid mixture (0.01 or 0.04%). The organisms grew rapidly in most conventional mycoplasma culture medium formulations containing horse or fetal bovine serum or a bovine serum fraction and under either aerobic or anaerobic environments. The optimum temperature for growth was 28"C, but multiplication occurred over a temperature range from 20 to 35°C. Both strains catabolized glucose and mannose, but did not hydrolyze arbutin, arginine, or urea. The molecular mass of the genome of strain F7T was determined to be about 886 megadaltons, while the base composition (guanine-plus-cytosine content) of the DNA was found to be 30.0 mol%. The two isolates were serologically unrelated to type strains of the 11 previously described Acholeplasma species and to 10 other unclassified sterol-nonrequiring mollicutes cultivated from various animal, plant, or insect sources. Strain F7 (= ATCC 49495) is the type strain of Acholeplasma seiflertii sp. nov.The occurrence of nonhelical, wall-less prokaryotes (class Mollicutes) on plant surfaces was first well documented in 1979 (9,15) when organisms with the general features of both Acholeplasma and Mycoplasma species were isolated from the surfaces of several tropical floral plants. Subsequent characterization of these strains and other new isolates from plant surfaces (22) showed that some of the strains were related to established sterol-nonrequiring Acholeplasma species that occur in vertebrate hosts (e.g., Acholeplasrna axanthum , Acholeplasma oculi, and Acholeplasma laidlawii) (9, 22). Other isolates represented either new Acholeplasma species (14, 33) or possibly sterol-requiring Mycoplasma species (9,22,26).While the presence of sterol-requiring Mycoplasma species on plant surfaces was suspected from the studies reported in 1979 to 1982 (15, 22), the possibility that these organisms might represent sterol-requiring, nonhelical forms of the genus Spiroplasrna could not be excluded at the time. The occurrence of Mycoplasma species on plant surfaces was confirmed recently when two of the strains from the early studies (17, 29) were fully characterized. In addition, sterol-requiring mollicutes were isolated from insect guts and from hemolymph samples (30), and four of these strains were characterized recently as new insect-derived Mycoplasma species (28, 34).The natural occurrence of acholeplasmas in the guts and hemolymph of in...

Bacterial Root Microbiome of Plants Growing in Oil Sands Reclamation Covers

“…Acholeplasma are wall-less bacteria from the phylum Firmicutes and close relatives of Phytoplasmas , whereas Acholeplasma s are not known to be pathogenic ( Kube et al, 2014 ). Acholeplasmas are also known to colonize the guts and hemolymph of insects ( Tully et al, 1988 ) and transmission to plants occurs when these insects feed on plant tissues ( Bonnet et al, 1991 ). In our study, barley plants may be more susceptible to insect feeding than clover plants and, hence, a higher incidence of Acholeplasma species in barley.…”

Microbiome Analysis Revealed Acholeplasma as a Possible Factor Influencing the Susceptibility to Bacterial Leaf Blight Disease of Two Domestic Rice Cultivars in Vietnam

“…Extracellular enzymes degrading plant cell walls like cellulase and amylase were found in Acholeplasma , which might support them to enter the host plant tissues ( Kube et al, 2014 ). Further, Acholeplasma has been detected in association with diverse insect species that feed on plant tissues ( Tully et al, 1994a ), and by the way can be transmitted into plants ( Bonnet et al, 1991 ). Apparently, in the LA cultivar, Acholeplasma lives symbiotically inside host plants’ tissues without harming the hosts.…”

Notes: Revised Taxonomy of the Class Mollicutes: Proposed Elevation of a Monophyletic Cluster of Arthropod-Associated Mollicutes to Ordinal Rank (Entomoplasmatales ord. nov.), with Provision for Familial Rank To Separate Species with Nonhelical Morphology (Entomoplasmataceae fam. nov.) from Helical Species (Spiroplasmataceae), and Emended Descriptions of the Order Mycoplasmatales, Family Mycoplasmataceae

“…Since these flower-associated strains apparently grew in the absence of serum or cholesterol, they were named Acholeplasma florum (18). Two additional serologically distinct species, again of insect or plant origin and with similar growth properties, were described more recently as Acholeplasma entomophilum (42) and Acholeplasma seiflertii (1).…”

“…florum (18,40) and subsequently applied to other insect and plant mollicutes (1,42,44,45,52) provides a consistent phenotypic marker for identification of strains that are capable of growing in the presence of 0.04% Tween 80. A simplified method for testing sterol requirements, including measuring growth promotion with Tween 80, has recently been proposed (31).…”