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A total of 39 strains assigned to the strictly anaerobic species Butyn'vibrio Jibrisolvens were examined for deoxyribonucleic acid (DNA) relatedness. The guanine-plus-cytosine (G+ C) base contents determined from the buoyant densities of chromosomal DNAs of 27 strains were 39.0 to 42.0 mol%. Another nine strains had G+C contents of 42.0 to 45.0 mol%, and three other strains had higher G+C contents (46.4 to 49.2 mol%). Genetic relationships among the strains were determined by DNA hybridizations, using both spectrophotometric and membrane filter techniques. The relationships derived by both methods are compared. The G+C content and hybridization results indicate that the strains comprise a genetically heterogeneous group, representing a number of distinct species. Strain D1, the type strain of B . Jibrisolvens, was not closely related to any of the other 38 strains. Five groups of related bacteria, encompassing 20 B utyrivibn'o strains, were identified as forming five separate species. The largest group identified by DNA relatedness as belonging to the same species contained only six strains. The other 19 strains were not closely related to any other strain.The genus Butyrivibrio is composed of obligately anaerobic, curved rod-shaped bacteria that ferment carbohydrates with production of large amounts of butyric acid. Members of the genus Butyrivibrio occur widely in nature and are among the most numerous bacteria isolated from the gastrointestinal tracts of animals fed a wide variety of rations. Strains have been isolated in high numbers from the rumina of cattle (4), sheep (8), Zebu cattle (27), goats (11), Alaskan reindeer (lo), and Svalbard reindeer (31) and from the ceca of sheep (25) and pigs (32). These strains show great phenotypic variability and are capable of fermenting a wide variety of substrates (4, 7, 8, 17, 22). Because of these characteristics butyrivibrios are probably one of the most important bacteria involved in gastrointestinal tract fermentation.The genus was originally described by Bryant and Small (4) and contained a single species, Butyrivibrio jibrisolvens. These workers isolated 48 strains of butyrivibrios, but found so much variation in the morphological and physiological characteristics of the strains that no attempt was made to define additional species. Since then, a number of other new strains have been added to the genus, and these strains also display much phenotypic diversity. In the absence of a comprehensive genetic and taxonomic analysis, new isolates routinely have been classified as Butyrivibrio jibrisolvens, although there are obvious differences among these isolates.Several attempts have been made to subdivide the genus. Hungate (22) proposed the addition of another species, "Butyrivibrio alactacidigens," to accommodate those strains that do not produce lactic acid in the fermentation of carbohydrates. Shane et al. (35) proposed dividing the genus into two groups based on the nutritional requirements of the strains and their ability to utilize or produce lactate, acetat...

A PCR system that can quickly and accurately identify 14 species of human pathogenic yeasts was developed. The procedure distinguished between nine species of a closely related clade, Lodderomyces elongisporus, Candida parapsilosis, a newCandida sp., C. sojae, C. tropicalis, C. maltosa, C. viswanathii,C. albicans, and C. dubliniensis and between another five more divergent species, Pichia guilliermondii,C. glabrata, C. zeylanoides, C. haemulonii, and C. haemulonii type II. A rapid DNA extraction procedure that yields purified DNA in about 1 h is also described. The system uses uniform conditions with four primers for each reaction, two 40- to 50-mer universal primers that serve as a positive control and two 23- to 30-mer species-specific primers. Species-specific primers were derived from a 600-nucleotide variable region (D1/D2) at the 5′ end of the large-subunit (26S) ribosomal DNA gene and were generally designed to use mismatches at the 3′ end. Universal primers were developed from conserved nucleotide sequences in the small-subunit (18S) rRNA gene. In this system, a control 1,200- to 1,300-base DNA fragment was produced in all reactions and a smaller 114- to 336-base DNA fragment was produced if the chromosomal DNA from the target species was present. The PCR procedure is rapid and easy to interpret and may be used with mixed cultures.