- Volume 35, Issue 4, 1985

The etiological agent of equine monocytic ehrlichiosis (synonym, Potomac horse fever) was isolated and propagated in vitro by using techniques similar to those established for some members of the genus Ehrlichia. The organisms, which are contained within a cytoplasmic vacuole, are intermediate in size between Ehrlichia canis and Ehrlichia sennetsu, ranging from 0.4 to 0.75 μm wide and from 0.5 to 1.5 μm long. The agent is antigenically related to E. sennetsu and E. canis but also possesses unique antigenic determinants, thereby distinguishing it as a new species of the genus Ehrlichia. The name Ehrlichia risticii is proposed for this new agent. The type strain is strain HRC-IL (= ATCC VR-986).

Among the mycoplasmal species commonly isolated from porcine lungs are Mycoplasma hyopneumoniae and Mycoplasma flocculare. The former organism is a proven agent of enzootic porcine pneumonia, whereas the latter organism is of little or no pathogenicity. These mycoplasmas show considerable antigenic cross-reactivity. The deoxyribonucleic acids of M. hyopneumoniae strain 11 and M. flocculare strain Ms42T (T = type strain) each had a guanine-plus-cytosine content of 33 mol%. We also determined the extent of deoxyribonucleic acid sequence homology as reflected in deoxyribonucleic acid-deoxyribonucleic acid hybridization values. Approximately 10% heterologous hybridization was observed. Thus, our data support the previous classification of these organisms as separate species within the genus Mycoplasma.

Monoclonal antibody MAI-6 directed against Pseudomonas aeruginosa strain PAO1 outer membrane lipoprotein H2 also interacted with a protein having an identical molecular weight from 50 of 52 strains of P. aeruginosa tested. This antibody interacted with the P. fluorescens group of the family Pseudomonadaceae and with Azotobacter vinelandii but not with several other species of gram-negative bacteria. A colony blotting assay performed with this antibody allowed rapid detection of the P. fluorescens-A. vinelandii group.

The guanine-plus-cytosine contents of Rothia dentocariosa strains ATCC 17931T (T = type strain) and ATCC 19426 were determined by thermal denaturation and found to be 54 and 57 mol%, respectively. These values are lower than the values given in many publications, but are consistent with data cited in some other references.

The total deoxyribonucleic acids from 10 strains of an undescribed cactophilic species of Clavispora were subjected to restriction analyses with endonucleases ApaI, EcoRI, KpnI, and XholI. A 7.6-kilobase tandemly repeated segment of the genome was mapped and found to possess both conserved regions and variable regions among the strains examined. A total of eight possible endonuclease recognition sites were identified. Two strains were heterogeneous, and one of these shared one of its restriction maps with three other strains. In one instance, variation was correlated with a habitat difference. In addition, all strains possessed very large (up to 28-kilobase) repetitive EcoRI fragments. Preliminary results indicate that this yeast species shares parts of its conserved region with Clavispora lusitaniae, but that there are major differences between the two species in their variable regions. The use of restriction mapping in taxonomic and other investigations of yeasts is discussed.

Twenty-four species assigned to the genus Saccharomyces sensu stricto were examined for deoxyribonucleic acid relatedness. Results with type strains demonstrated the presence of four distinct species: S. cerevisiae, S. bayanus, S . carlsbergensis, and S . kluyveri. S . carlsbergensis NRRL Y-12693T showed intermediate relatedness between S . cerevisiae and S . bayanus and has a genome size approximately 1.5 times those of the last two species. These data suggest S . carlsbergensis to be a partial amphidiploid which may have arisen from natural hybridization between S. cerevisiae and S . bayanus.

The Judicial Commission has formally and explicitly ruled that the nomenclatural types cited in the Approved Lists are the correct types unless later varied by the Commission under its powers. The type species of Nocardia becomes Nocardia asteroides and the type species of Pasteurella becomes Pasteurella multocida, superseding the types cited in Opinion 13. Pasteurella gallicida is placed on the list of nomen rejicienda.

The Judicial commission designated NCIB 11664 as the type strain of Acetobacter aceti subsp. xylinum in place of strain ATCC 23767, which is a Gluconobacter sp.

The name Yersinia pseudotuberculosis subsp. pestis (van Loghem) Bercovier et al. 1981 has been rejected by the Judicial Commission of the International Committee on Systematic Bacteriology because of practical concerns about human welfare.