Large plasmids in ruminal strains of Selenomonas ruminantium

The plasmid content of six different isolates of Selenomonas ruminantium from the rumen of sheep, cows or goats was examined by electron microscopy. In addition to small plasmids (< 12 kb) studied previously, all six strains contained at least one plasmid larger than 20 kb. Plasmid sizes of 1·4, 2·1, 2·4, 5·0, 6·2, 20·4, 20·8, 22·7, 23·3, 29·3, 30·7, 34·4 and 42·6 kb were estimated from contour length measurements. DNA-DNA hybridization experiments revealed homology among the large plasmids from five strains, while the 20·8 kb plasmid from a sixth isolate showed no apparent relationship with the plasmids of the other strains.     

Refined localization of the pyruvate dehydrogenase E1α gene (PDHA1) by linkage analysis

Pyruvate dehydrogenase (PDH) E1α is a key component in the PDH complex which catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA. Defects in the gene coding for PDH E1α (PDHA1) are associated with a variety of clinical symptoms, often of a severe character. In the present study, the segregation of three polymorphic CA repeats located in PDHA1 was followed in the 40 CEPH reference pedigrees. Using these data, multipoint linkage analysis was carried out, refining the genetic location of PDHA1. The 16-point map presented locates PDHA1 in an approximately 3-cM interval between DXS999 and DXS365 with odds of more than 1000 : 1. From known physical localizations of the flanking marker loci, PDHA1 could be regionally assigned to Xp22.1-p22.2. The information provided should be of value in clinical settings. Received: 10 May 1996     

A new class of reversible cell cycle inhibitors

The effects of three compounds on the cell cycle of HL-60 promyeloid leukemia cells has been examined. Ciclopirox olamine, an antifungal agent, and the compound Hoechst 768159 reversibly block the cell cycle at a point occurring roughly 1 h before the arrest mediated by aphidicolin, an inhibitor of DNA polymerase alpha activity, which acts in early S phase. Similar results are also obtained with the compound mimosine, a plant amino acid. Based on these data, it is concluded that all three agents inhibit cell cycle traverse at or very near the G1/S phase boundary and identify a previously undefined reversible cell cycle arrest point.     

Genetic diversity in Selenmonas ruminantium isolated from the rumen

Abstract Non-denaturing polyacrylamide gel electrophoresis was used to detect genetic variation at loci coding for there intracellular enzymes in the obligately anaerobic rumen bacterium Selenomonas ruminantium . Four mobility variants were detected for lactate dehydrigenase, seven for glucokinase and at least five for NADP-dependent glutamate dehydrogenase among 28 newly isolated, and eitght previously isolated strains from sheep and cattle. No evidence was found for an exclusive association of any particular electrophoretic mobility type with variable metabolic traits such as the ability to utilise lactate, to reduce nitrate or to ferment trehalose, sorbitol, rhamnose or glycerol. The most commonly occurring electromorph type was recovered from more than one animal, while most animals examined were show to harbour more than one electromorph type.