Syntrophus buswellii, which was isolated from anaerobic digestor sludge and is present in aquatic sediments, is a motile, gram-negative, anaerobic rod-shaped organism that requires coculture with an appropriate hydrogenotroph for growth. This bacterium produces acetate, C02, and H2 (or formate) from benzoate and, possibly, hydrocinnamate (phenyl-3-propionate). A detailed description is given.

Quin's oval is a relatively large bacterium often seen in the rumens of sheep fed diets containing some readily fermented carbohydrates. It has not been obtained in axenic cultures, but a number of its features have been determined by various methods, such as studying cell suspensions purified from rumen fluid by differential centrifugation. We obtained similarly purified suspensions from a sheep fed a diet containing a large amount of molasses. Nearly complete 16s rRNA sequence analysis of these cells as well as cells of Selenomonas ruminantiurn subsp. ruminantiurn GA192 (ATCC 12561; type strain) and S. ruminantium subsp. Zuctii'ytica HD, (ATCC 27209) was done. These sequences were compared with those of other bacteria. Evolutionary distance estimates indicated that Quin's oval was most closely related to the Selenomonas-Megasphaera-Sporomusa group in the gram-positive phylum but that it belongs in a new genus. We propose the name Quinella ovalis gen. nov., sp. nov., with its description based on previously known features.Quin's oval (QO) was briefly described by Woodcock and Lapage in 1913 (27) and separately discovered by Quin (16) in 1943. Quin found it in large numbers in the rumens of sheep fed diets of sugar-rich fresh alfalfa either alone or supplemented with molasses, sucrose, or glucose. Although he did not isolate it, he named it "Schizosaccharomyces ovis" because of its yeast-like (gassy) rapid fermentation of sugar, its relatively large (4-by-8 pm) oval to oblong-oval shape, and its reproduction by binary fission. He also found that it produces glycogen intracellular reserve material from part of the sugar used.Further studies on QO have been hampered by the inability of researchers to obtain pure cultures; however, a considerable number of its features have been determined by various techniques. For example, Howard and coworkers (2, 6, 23) obtained highly enriched cells by differential centrifugation of rumen fluid from sheep fed diets that promoted the growth of large numbers of 00. Using these suspensions, they obtained information on the carbohydrate fermented and the products produced and definitive information on glycogen storage. They also determined that since the cell walls of QO were shown to contain 2,4-diaminopimelic and muramic acids, it is a bacterium. Other studies, such as those of Orpin (13), which used very slow and meticulous culture techniques, have confirmed and extended the information on carbohydrate fermentation, motility, gram-negative staining, and several other features.QO is considered an important part of the microbiota of the rumens of sheep, and it occurs in numbers from 1.9 x lo5 to 3.0 x 108/ml (13). It has been found in numbers as high as 1Ol1/ml (21) in sheep fed mainly molasses. While no taxonomic information has been published on QO since the definitive studies showing that it is a bacterium (23), one of us (M.P.B.) has long surmised that it is at least * Corresponding author. somewhat related to Selenomonas ruminantium subspecies (4,15). Its fermentation produ...

Methanogenic enrichments catabolizing 13 mM phenylacetate or 4 mM phenol were established at 37°C, using a 10% inoculum from a municipal anaerobic digester. By using agar roll tubes of the basal medium plus 0.1% yeast extract-25 mM fumarate, a hydrogenotrophic lawn of Wolinella succinogenes and phenol or phenylacetate, strains P-2 and PA-1, respectively, were isolated in coculture with W. succinogenes. With the lawn deleted, PA-1 was isolated in pure culture. Strain P-2 is apparently a new species of anaerobic, motile, gram-negative, spindle-shaped, small rod that as yet has been grown only in coculture with W. succinogenes. It used phenol, hydrocinnamate, benzoate, and phenylacetate as energy sources. Product recovery by the coculture, per mole of phenol and 4.4 mol of fumarate used, included 2.03, 0.12, 0.08, and 3.23 mol, respectively, of acetate, propionate, butyrate, and succinate. Carbon recovery was 75% and H recovery was 80%, although CO2 and a few other possible products were not determined. That P-2 is an obligate proton-reducing acetogen and possible pathways for its degradation of phenol are discussed. Strain PA-1 is apparently a new species of anaerobic, motile, relatively small, gram-negative rod. It utilized compounds such as phenylacetate, hydrocinnamate, benzoate, phenol, resorcinol, gallate, 4-aminophenol, 2-aminobenzoate, pyruvate, Casamino Acids, and aspartate as energy sources in coculture with W. succinogenes. Per mole of phenylacetate and 1.44 mol of fumarate used, 1.04, 0.53, and 0.78 mol of acetate, propionate, and succinate, respectively, were recovered from the coculture. Only about 50% of the carbon and H were recovered. In coculture with Methanospirillum hungatei, 0.96 mol of acetate and 0.25 mol of methane were recovered per mol of pyruvate used; 0.90 mol of acetate and 0.33 mol of methane, per mol of fumarate used; 0.93 mol of acetate and 0.54 mol of methane, per mol of aspartate used; and 1.71 mol of acetate and 0.57 mol of methane, per mol of glucose used. Carbon and H recoveries, assuming CO2 and ammonia were produced in stoichiometric amounts, were 97 and 98% for pyruvate, 72.5 and 82% for fumarate, 96.5 and 98% for aspartate, and 61.8 and 76% for glucose. No explanation such as contamination could be found for the fact that the coculture PA-1 plus Wolinella sp. did not use glucose; after growth with M. hungatei on pyruvate, however, the latter coculture used glucose. The PA-1 pure culture produced 0.86 mol of propionate per mol of succinate used during growth. PA-1 produced a small amount of H2. Strain PA-1 is the most versatile anaerobic bacterium yet known that catabolizes monobenzenoids in the absence of electron acceptors such as sulfate or nitrate.

Two rumen-cannulated wether sheep were fed a diet containing 1 kg of a liquid-molasses mixture, 80 g of soybean oil meal, and 100 g of chopped wheat straw once a day. In 6 weeks and thereafter, the microbiota adapted such that Quin's oval, a very large bacterium, was present in huge numbers (11.3 x 1010 and 1.3 x 1010 ml-' after 73 days). Direct microscopic counts were also done on small bacteria, moderate-sized Selenomonas spp., and small Entodinium spp., which were the only protozoa seen. After the necessary dilution of rumen contents to make the microbial cells visible, Quin's ovals were seen to be much smaller in sheep 1 than in sheep 2. Most-probable-number estimates indicated that Methanobrevibacter spp. were present at 107 ml-', Methanosarcina spp. were present at 103 ml-', and Eubacterium limosum-like bacteria were present at 105 to

Strain PA-1 (S. Barik, W.J. Brulla, and M.P. Bryant, Appl. Environ. Microbiol. 50:304-310, 1985) is an anaerobic, gram-negative rod that in pure culture decarboxylates succinate to propionate and that grows syntrophically as an acetogen with the H2 utilizer Methanospirillum hungatei if glucose, pyruvate, aspartate, or fumarate is provided. In pure culture, strain PA-1 grows optimally in a medium containing 5% ruminal fluid, 0.1% yeast extract, a 4:1 N2-CO2 gas phase, and 20 mM succinate. With the PA-1 plus M. hungatei coculture, good growth was obtained with 7.5 mM glucose and tryptophan could replace the yeast extract. Strain PA-1 in pure culture grew quite well in glucose medium if the large headspace was flushed intermittently with N2. Flushing with H2 inhibited this growth.