Identification of saccharolytic enzymes ofZymomonas mobilis CP4

Studies on sucrose hydrolysis withZymomonas mobilis CP4 have revealed, via electrophoresis and zymogram staining, three enzymes that hydrolyze sucrose. One electrophoretic band corresponds to the well characterized levansucrase, while the two remaining bands appear to be invertases (Inv A and Inv B). Inv A occurs intracellularly in CP4, while Inv B occurs in the supernatant as well as intracellularly.     

Fermentation of L-aspartate by a saccharolytic strain of Bacteroides melaninogenicus.

Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented.     

Fermentation of L-aspartate by a saccharolytic strain of Bacteroides melaninogenicus.

Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented.     

Characteristics of Clostridium thermocellum strain SS8: A broad saccharolytic thermophile

Clostridium thermocellum SS8 produced both carboxymethylcellulase (CMCase) and Avicelase when grown on cellulose. CMCase activity was unaffected by Ca²⁺, Mg²⁺, dithionate or dithiothreitol (DTT). Avicelase activity increased 2-fold with 5 mM DTT and 10 mM Ca²⁺. Cellulase and amylase were produced when a celluloseadapted culture was grown on starch. The mould grew best on sucrose and was inhibited by NaCl above 10 g/l.     

Chitin degradation by Clostridium sp. strain 9.1 in mixed cultures with saccharolytic and sulfate-reducing bacteria

Abstract The fermentation of chitin was studied in pure and cocultures of the chitinolytic Clostridium strain 9.1 and various non-hydrolytic sugar-fermenting and sulfate-reducing bacteria. A 5- to 8-fold enhancement of the rate of chitin degradation was observed, which was not due to the alleviation of inhibition of the chitinolytic enzyme system by polymer hydrolysis products. This was concluded from the observation that rates of chitinolysis and fermentation were unaffected by the addition of N -acetylglucosamine (NAG) or NAG-oligomers to pure cultures of strain 9.1, and from the absence of an unequivocal relation between the ability of a secondary bacterium to consume potentially inhibitory hydrolysis products and its capacity to stimulate chitin degradation. The acceleration of chitin fermentation in the presence of sugar-fermenting bacteria was the result of a release by these secondary populations of growth factors essential to strain 9.1. These factors comprised a high molecular, thioredoxin-like compound responsible for enhanced chitinolytic activity [10], and various low molecular compounds necessary for optimal growth. The sulfate reducers (except Desulfovibrio sp. strain 20028) released primarily the high molecular growth factor in coculture with strain 9.1. NAG-fermenting bacteria consumed approximately 10% of the hydrolysis products, whereas species capable of utilizing both mono- and oligomeric sugars fermented at least 50% of the sugars produced by strain 9.1. Nevertheless, the rate of chitinolysis in these cocultures proceeded at very similar rates.
The observed interactions between Clostridium sp. strain 9.1 and the secondary populations are discussed in relation to the results from studies on mixed culture fermentations of cellulosic substrates reported in the literature.     

Pyruvate oxidation by the Reiter strain of Treponema phagedenis.

Spectrophotometric assays of pyruvate oxidation catalyzed by extracts of the Reiter strain of Treponema phagedenis indicated that viologen dyes, flavin nucleotides, and a ferric iron chelate, but not pyridine nucleotides, were utilized as electron acceptors. Benzyl viologen-linked activity partially sedimented during ultracentrifugation and appeared similar to clostridial pyruvate:ferredoxin oxidoreductase with respect to the spectral properties of the enzyme chromophore. Electron carrier activity in treponemal extracts was quantitated by a metronidazole-linked assay in which the oxidation of pyruvate by carrier-depleted extracts led to the reduction of electron carrier in the crude extracts which then reduced metronidazole. The rate of metronidazole reduction was proportional to the amount of electron carrier present in the assay. Electron carrier activity in Triton X-100-solubilized, crude extracts partially purified by DEAE-cellulose chromatography and gel filtration was attributed to a protein possessing the spectral and physical properties of a ferredoxin. A similar protein appeared to be present in extracts of Treponema denticola ST10.     

Isolation of saccharolytic dissimilatory sulfate-reducing bacteria

Abstract Four unidentified saccharolytic dissimilatory sulfate-reducing strains were isolated from an anaerobic digester. Cells were Gram-negative, motile, nonsporulating rods which differ markedly from known sulfate reducers especially with respect to carbon source utilisation and sulfur sources which can be reduced. The strains were capable of metabolising at least 26 out of 50 carbohydrates tested. Carbohydrates were, in the absence of exogenous sulfate, fermented to acetate, ethanol, lactate, carbon dioxide and hydrogen. In the presence of excess sulfate carbohydrates were fermented to acetate, ethanol, carbon dioxide, hydrogen and hydrogen sulfide, but lactate was not detected. An oxidized organic or inorganic sulfur source, including elemental sulfur, was not required as a prerequisite for growth on carbohydrates, Lactate was, in the presence of sulfate, converted to acetate, ethanol, carbon dioxide, hydrogen and hydrogen sulfide. In the absence of sulfate no lactate was utilised and no growth was observed.     

Magnetobiology: the kT paradox and possible solutions

The article discusses the so-called 'kT problem' with its formulation, content, and consequences. The usual formulation of the problem points out the paradox of biological effects of weak low-frequency magnetic fields. At the same time, the formulation is based on several implicit assumptions. Analysis of these assumptions shows that they are not always justified. In particular, molecular targets of magnetic fields in biological tissues may operate under physical conditions that do not correspond to the aforementioned assumptions. Consequently, as it is, the kT problem may not be an argument against the existence of non thermal magnetobiological effects. Specific examples are discussed: magnetic nanoparticles found in many organisms, long-lived rotational states of some molecules within protein structures, spin magnetic moments in radical pairs, and magnetic moments of protons in liquid water.     

Complete genome sequence of Treponema succinifaciens type strain (6091)

Treponema succinifaciens Cwyk and Canale-Parola 1981 is of interest because this strictly anaerobic, apathogenic member of the genus Treponema oxidizes carbohydrates and couples the Embden-Meyerhof pathway via activity of a pyruvate-formate lyase to the production of acetyl-coenzyme A and formate. This feature separates this species from most other anaerobic spirochetes. The genome of T. succinifaciens 6091(T) is only the second completed and published type strain genome from the genus Treponema in the family Spirochaetaceae. The 2,897,425 bp long genome with one plasmid harbors 2,723 protein-coding and 63 RNA genes and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Induction of saccharolytic enzymes by sucrose in Bacillus subtilis: evidence for two partially interchangeable regulatory pathways.

Sucrose induces two saccharolytic enzymes in Bacillus subtilis, an intracellular sucrase and an extracellular levansucrase, encoded by sacA and sacB, respectively. It was previously shown that the sacY gene encodes a positive regulator involved in a sucrose-dependent antitermination upstream from the sacB coding sequence. We show here that the sacY product is not absolutely required for sacB induction: a weak but significant induction can be observed in strains harboring a sacY deletion. The sacY-independent induction was altered by mutations located in the sacP and sacT loci but was observed in both sacU+ and sacU32 genetic backgrounds. These results suggest that B. subtilis has two alternative systems allowing sacB induction by sucrose. Both systems also seem to be involved in sacA induction.     

Fumarate reduction and product formation by the Reiter strain of Treponema phagedenis.

The catabolic pathways for butyrate, acetate, succinate, and ethanol formation by the Reiter strain of Treponema phagedenis were investigated. Enzyme activities were demonstrated for glucose catabolism to pyruvate by the Embden-Meyerhof-Parnas pathway. Butyrate formation from acetyl-coenzyme A (acetyl-CoA) does not generate ATP by substrate level phosphorylation and involves NAD+-dependent 3-hydroxybutyryl-CoA dehydrogenase and NAD(P)+-independent butyryl-CoA dehydrogenase activities. Butyrate is formed from butyryl-CoA in a CoA transphorase reaction. Phosphate acetyltransferase and acetate kinase activities convert acetyl-CoA to acetate. An NADP+-dependent alcohol dehydrogenase participates in ethanol formation; however, the manner in which acetyl-CoA is reduced to acetaldehyde is unclear. A membrane-associated fumarate reductase was found which utilized reduced ferredoxin or flavin nucleotides as physiological electron donors. Additional electron carriers may also be involved in electron transfer for fumarate reduction. Strains of Treponema denticola, T. vincentii, and T. minutum utilized fumarate without succinate formation, whereas strains of T. phagedenis and T. refringens formed succinate from exogenously supplied fumarate.     

Numerical taxonomy of some non-saccharolytic and saccharolytic Bacteroides species

Various Bacteroides spp. were examined by physiological tests, presence of specific enzymes, antibiotic sensitivity, menaquinone composition and a few miscellaneous tests. The data matrix containing 58 strains and 55 unit characters was examined using Gower's similarity coefficients (S _G ) and included matching negative character states and multistate characters. The highly saccharolytic strains were separated from the less saccharolytic and non-fermentative strains at the 55% similarity level; while at the slightly higher level of 63% strains of Capnocytophaga (formerly Bact. ochraceus ) were recovered as a compact phenon distinct from other saccharolytic species. The phenogram was divided into 6 clusters at 72% similarity level. Most of the ' Bact. fragilis group' of species clustered in one phenon while Bact. melaninogenicus ssp. melaninogenicus, Bact. bivius and a new species, Bact. denticola , formed another group. Another phenon comprised the saccharolytic non-pigmented species closely related to Bact. oralis such as Bact. buccalis and Bact. pentosaceus. The less saccharolytic strains of Bact. melaninogenicus ssp. intermedius and Bact. disiens were recovered in a distinct phenon. The low affinity (less than 55% similarity) between the two subspecies of Bact. melaninogenicus emphasised the need for reclassifying these taxa into separate species. The non-fermentative and very weakly saccharolytic strains formed good taxospecies. The separation of this cluster into three subclusters is in excellent agreement with chemotaxonomic data now available.