- Volume 42, Issue 3, 1992

The complex cell envelope profile of the anaerobic, spore-forming, xylanolytic eubacterium Clostridium xylanolyticum ATCC 49623 (G. M. Rogers and A. A. W. Baecker, Int. J. Syst. Bacteriol. 41:140-143, 1991) was investigated in greater detail. Although growing cells of this organism produced a gram-negative staining reaction, electron microscopy of thin sections of cells clearly revealed a gram-positive cell envelope profile. The cell wall consists of a thin peptidoglycan layer with a regularly arranged surface layer outside it. Older cells in the stationary phase may have surface layers on both sides of the peptidoglycan, providing a multilayer thin-section profile. Freeze-etched preparations of whole cells revealed an oblique surface layer lattice (a = 6.6 nm; b = 5.3 nm; γ ∼ 78°). The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of a solubilized whole-cell extract indicated that the molecular mass of the surface layer monomer was approximately 180 kDa. Treatment of the gels with periodic acid-Schiff reagent resulted in a weak, but unambiguously positive staining reaction. Our data indicate that a glycosylated surface layer protein is present on the cell surface of C. xylanolyticum.

The 16S ribosomal DNA sequence of Cowdria ruminantium, the causative agent of heartwater disease in ruminants, was determined. An analysis of this sequence showed that C. ruminantium forms a tight phylogenetic cluster with the canine pathogen Ehrlichia canis and the human pathogen Ehrlichia chaffeensis. Although a close relationship between the genus Cowdria and several members of the tribe Ehrlichieae has been suspected previously, the tight phylogenetic cluster with E. canis and E. chaffeensis is surprising in view of known differences in host preference and target cells.

The type strain (strain ICMP 4289) and two reference strains (strains ICMP 4290 and ICMP 4291) of Pseudomonas cissicola (Takimoto 1939) Burkholder 1948 were obviously mislabeled at the Plant Disease Division Culture Collection (presently the International Collection of Microorganisms from Plants) in New Zealand when they were deposited in 1975 or subsequently when they were coded for the catalog of the collection. The strains were also mislabeled at the National Collection of Plant Pathogenic Bacteria in England when strain NCPPB 2982T (T = type strain) was transferred from the Plant Disease Division Culture Collection. Recently, these errors have caused considerable confusion in the taxonomic placement of this bacterium, not only in workers who received cultures from the culture collections but also in workers who are directly responsible for the culture collections. The type strain of the bacterium should be strain PC1 in the culture collection of plant-pathogenic bacteria at the Laboratory of Plant Pathology, Shizuoka University, strain ATCC 33616 in the American Type Culture Collection, or strain CCM 2888 in the Czechoslovak Collection of Microorganisms.

We investigated 22 mycoplasma and acholeplasma species for their ability to reduce tetrazolium salts by using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The test results were evaluated visually, as well as spectrophotometrically, by using an enzyme-linked immunosorbent assay reader. Our results were very similar to the results obtained when the tetrazolium salt reduction assay described by Aluotto et al. was used. However, the MTT reduction assay appeared to be better because it is faster, more objective and sensitive, easier to evaluate, and less expensive; in addition, it allows quantitative determinations. By using regression analysis a linear correlation between formazan production and the number of colony-forming units was demonstrated for all of the species investigated, indicating that the MTT assay can also be used for growth, toxicity, or chemosensitivity tests for the mycoplasma species that are capable of reducing tetrazolium salts.

A ribosomal DNA restriction analysis of 17 strains belonging to the Saccharomyces cerevisiae complex revealed two major groups, one of which corresponded to Saccharomyces bayanus. Our results generally correlate with previously reported genetic and molecular data and support the conclusion that S. bayanus should be reinstated as a separate taxon.