Metabolic characteristics of an aerobe isolated from a methylotrophic methanogenic enrichment culture.

An anaerobic methylotrophic methanogenic enrichment culture, with sustained metabolic characteristics, including that of methanation for over a decade, was the choice of the present study on interspecies interactions. Growth and methanation by the enrichment were suppressed in the presence of antibiotics, and no methanogen grown on methanol could be isolated using stringent techniques. The present study confirmed syntrophic metabolic interactions in this enrichment with the isolation of a strain of Pseudomonas sp. The organism had characteristic metabolic versatility in metabolizing a variety of substrates including alcohols, aliphatic acids, amino acids, and sugars. Anaerobic growth was favoured with nitrate in the growth medium. Cells grown anaerobically with methanol, revealed maximal nitrate reductase activity. Constitutive oxidative activity of the membrane system emerged from the high-specific oxygen uptake and nitrate reductase activities of the aerobically and anerobically grown cells respectively. Cells grown anaerobically on various alcohols effectively oxidized methanol in the presence of flavins, cofactor FAD and the methanogenic cofactor F420, suggesting a constitutive alcohol oxidizing capacity. In cells grown anaerobically on methanol, the rate of methanol oxidation with F420 was three times that of FAD. Efficient utilization of alcohols in the presence of F420 is a novel feature of the present study. The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between the Pseudomonas sp. and the methanogen(s). Methylotrophic, methanogenic partnership involving an aerobe is a novel feature hitherto unreported among anaerobic syntrophic associations and is of ecological significance

Kinetics of biomethanation of solid tannery waste and the concept of interactive metabolic control.

Anaerobic digestion of calf skin collagenous waste was optimized for a batch process based on accelerated maximal methane yield per gram of input volatile solid. A kinetic analysis with respect to changes in the levels of volatile solid, collagen, amino sugars, amino acids, hydroxyproline, ammonium ions, and volatile fatty acid were followed for a period of 80 d. Distinct metabolic phases included an initial high rate collagenolysis for 4d, with 50% degradation and was followed by an acidogenic phase between 4-12 d with volatile fatty acids levels increasing to 215 mmol/L. Subsequently methanogenesis ensued and was maximal between 12-24 d when volatile fatty acids attained steady state levels. During the period of 80 d, the overall decrease in volatile solid level was 65%, whereas the collagen level declined by 85% with 0.45 L of methane yield/g of volatile solid degraded. Based on the levels of various metabolites detected, the concept of interactive metabolic control earlier proposed has been validated.

The primary structure of xylanase from Thermoascus aurantiacus.

The amino acid sequence of xylanase isolated from the culture medium of Thermoascus aurantiacus was determined. It had 269 amino acid residues with an alpha-N-acetyl group at the amino terminus. The structure of blocked N-terminal 11 amino acid tryptic peptide except for acetylalanine was determined by sequence analysis of peptides derived from partial acid hydrolysis and from thermolysin digestion. The blocked N-terminal amino acid was determined as N-acetylalanine by electron ionization mass spectrometry. The sequence comparison of xylanase from T. aurantiacus with the xylanases of alkalophilic Bacillus sp C-125 and Cryptococcus albidus showed 40% similarity. Xylanase from T. aurantiacus had up to 15% similarity with the other two xylanases known. All the five xylanases showed a higher degree of similarity at the level of secondary structure.

Proteinase-like activity in the cytotoxic factor produced by T cells during dengue virus infection.

Dengue type 2 virus (DV)-induced cytotoxic factor (CF) or the virus-primed spleen cell capable of secreting CF were treated with various proteinase inhibitors and their activity was assayed. It was observed that the cytotoxic activity of CF was inhibited significantly, in a dose-dependent manner, by pretreatment with bovine pancreatic trypsin inhibitor (BPTI) and phenylmethylsulphonyl fluoride (PMSF), to a lesser extent by soya-bean trypsin inhibitor (SBTI) and leupeptin and not at all by 1,10-phenanthroline (OP). Similar effects were observed by pretreatment of DV-primed spleen cells. Amidolytic activity of CF or its purified fractions was assayed using twelve chromogenic peptide substrates and all the substrates were hydrolysed to the varying extent. The amidolytic activity of CF was also inhibited by pretreatment with proteinase inhibitors. Thus, CF could be a proteinase with the distinction of having a broad spectrum of activity.