The growth of seven Thiobacillus ferrooxidans strains was trested on various solid media prepared according to previously published procedures in comparison with a series of new formulations (TSMs, Thiobacillus solid media) set up in our laboratory. These media differed in the type of gelling agent and in the concentration of phosphate and ferrous ions. It was determined that the established formulations brought qualitatively and quantitatively unsatisfactory results whereas, among the new media, TSM 1 produced quantitative yields of T. ferrooxidans colonies. The TSM1 supports the growth of T. ferrooxidans strains and can be recommended for the estimation of cell numbers in liquid cultures and for the isolation of single clones. There was also a noticeable similarity in the morphology of colonies formed by different T. ferrooxidans strains.
A large number of mercury-resistant nitrogen-fixing bacteria were isolated by screening soil samples from agricultural farms of West Bengal, India. All of the samples were found to contain significant quantities of mercury. Twenty five of the pure isolates were identified to the generic level following Bergey's Manual of Determinative Bacteriology, 8th edition. These organisms were resistant to HgCl2, and a few of them were resistant to phenylmercuric acetate (PMA) as well. Their mercury resistance was also associated with antibiotic resistance properties. Growth of two mercury-resistant N2-fixing organisms was monitored in liquid media supplemented with HgCl2. The mercury volatilizing capacity of four mercury-resistant bacterial strains was also determined.
Trimethylamine N-oxide (TMAO) reductase which is involved in anaerobic respiration is one of the molybdenum-containing enzymes in Escherichiacoli. A mutant defective in the activity of TMAO reductase was isolated by inserting phage MudI. The mutation was localized at 0.7min adjacent to chlG on the E. coli chromosome, and was designated torB. The torB mutant grown anaerobically with TMAO contained 10-30% of the enzyme activity in the parent strain grown under the same condition and about 80% of the enzyme protein immuno-reactive with an antiserum against the TMAO reductase. The content of molybdopterin, an organic moiety of molybdenum cofactor, in the immuno-precipitate from extracts of the torB mutant was rather low, about 60% of that in the immuno-precipitate from the parent strain. The mutant showed a normal level of another molybdenum enzyme nitrate reductase activity when anaerobically grown with nitrate. These findings suggest that the torB gene is involved in the formation of the active enzyme of TMAO reductase through the processing of molybdenum cofactor. There was a marked expression of torB under anaerobic conditions, and TMAO was not required for it.
Pyruvate-dependent nitrate reduction was observed in crude extractsprepared from Clostridium perfringens grown with nitrate. This reduction system was reconstituted, under nitrogen gas with ferredoxin (Fd), nitrate reductase (NaR) and fraction A which was previously isolated from a crude extract of the cells. Rubredoxin (Rd) functioned as an electron carrier in place of Fd. Fd was reduced with fraction A in the presence of coenzyme A (CoA) and pyruvate, indicating that the fraction A contains pyruvate: Fd oxidoreductase. We propose the following scheme for the electron transfer in pyruvate-dependent nitrate reduction system in C. perfringens: pyruvate→pyruvate: Fd oxidoreductase→Fd (Rd) →NaR→ nitrate.
The microbial populations and fermentation characteristics were compared in the rumina of two rumen-cannulated Holstein steers fed untreated rice straw (RS) and concentrate or ammonia-treated rice straw (ARS) and concentrate. The total volatile fatty acid concentrations in the rumina of both steers were significantly higher when they were fed ARS than when fed RS. The molar proportion of butyric acid when ARS was fed increased significantly, compared with the periods when was fed RS. The populationdensity of protozoa varied only insignificantly with RS or ARS diets. But Dasytricha spp. increased with RS and Entodinium spp. increased with ARS. The viable counts of cellulolytic bacteria were higher with ARS than with RS. The viable counts of sulfate reducing bacteria were lower with ARS, compared with the RS diet. Feeding ARS increased the viable bacterial populations such as Eubacterium spp., Fibrobacter succinogenes, Ruminococcus albus, and Succinivibrio spp. But Bacteroides spp. and Butyrivibrio spp. were dominant when RS was fed.
Gram-positive facultative methylotrophs were isolated by enrichment cultures with methanol as the sole source of carbon and energy. These bacteria were acid-fast, non-sporeforming, nonmotile rods, and grew on methanol and methylamine, but not on methane. The deoxyribonucleic acid base composition was 66 to 69mol% guanine plus cytosine. The cellular fatty acids consisted of a large amount of straight-chain saturated C16:0 acid, straight-chain unsaturated C16:1 and C18:1 acids, and 10-methyl C19:0 acid. The major quinone was menaquinone MK-9(H2). The principal amino acids in the cell wall was meso-diaminopimelic acid. There was a large amount of α-mycolic acid, a small amount of α′- ycolic acid and dihydroxy mycolic acid. The facultative methylotrophs appeared to be included in the genus Mycobacterium.
In the year 1986, we collected 85 samples of soil, plants and fruits from North Korea. We isolated 30 strains of yeast and yeast-like organisms (11 Ascomycetes, 9 Basidiomycetes, 7 Deuteromycetes and 3 arthroconidial fungi). The following genera were identified: Saccharomyces, Torulaspora, Pichia, Williopsis, Zygopichia, Hyphopichia, Debaryomyces, Geotrichum, Candida, Kloeckera, Rhodotorula, Sporobolomyces, Trichosporon and Aureobasidium.
The partitioning of electrons between methanogenesis and sulfate reduction in various conditions of anaerobic digestion of animal waste was calculated. Even in the presence of rather high concentrations of sulfate, methanogenesis was not suppressed much by sulfate reduction and under certain conditions almost the same amount of methane was produced irrespective of the presence or absence of sulfate. In the presence of rather high concentrations of propionate, sulfate was reduced depending strongly on propionate oxidation, and the total amount of electrons consumed by both methanogenesis and sulfate reduction was increased significantly by the sulfate reduction. When the concentration of propionate was low or nil, there were 2 types of partition of electrons. In one type, sulfate reduction achieved some reducing power by itself and the total amount of electrons consumed by both methanogenesis and sulfate reduction was increased somewhat by sulfate reduction. In the other type, sulfate reduction had no reducing power by itself and competitively inhibited methanogenesis. In the anaerobic digestion of animal waste, sulfate reduction may act mainly as a decomposes of intermediates of anaerobic digestion other than acetate, perhaps mainly propionate, and thus it stimulates the electron flow in the ecosystem.