Ligninolytic activity of Phanerochaete chrysosporium: Physiology of suppression by NH 4 + and l-glutamate

Previous research showed that addition of nutrient nitrogen to ligninolytic (stationary, nitrogen-starved) cultures of the wood-decomposing basidiomycete Phanerochaete chrysosporium causes a suppression of lignin degradation. The present study examined early effects on nitrogen metabolism that followed addition of NH ₄ ⁺ and l-glutamate at concentrations that yield similar patterns of suppression. Both nitrogenous compounds were rapidly assimilated (>80% in 6 h). Both caused an initial 80% or greater increase in the intracellular glutamate pool and had similar effects in increasing the specific activities of NADP- and NAD-glutamate dehydrogenases and glutamine synthetase. Differences between the effects of added NH ₄ ⁺ and glutamate showed that suppression was not correlated with intracellular pools of arginine or glutamine, nor was the maintenance of an elevated glutamate pool required to maintain the suppressed state. While a portion of the initial glutamate suppression could be attributed to an effect on central carbon metabolism through glutamate catabolism by NAD-glutamate dehydrogenase, the long term suppression by glutamate and the suppression by NH ₄ ⁺ were more specific. Suppression by NH ₄ ⁺ or glutamate in the presence or absence of protein synthesis (cycloheximide) followed essentially identical kinetics during 12 h. These results indicate that nitrogen additions cause a biochemical repression of enzymes associated with lignin degradation. Results are consistent with the hypothesis that nitrogen metabolism via glutamate plays a role in initiation of repression.Non-Standard Abbreviations DMS 2,2-dimethylsuccinate - TCA trichloroacetic acid     

β-endorphin-induced increase in striatal dopamine turnover

Human β-endorphin administered intracisternally in a dose of 15 μg per rat increased striatal concentrations of the dopamine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) as well as producing catalepsy. These effects were inhibited by naloxone. Pargyline-induced decreases in striatal DOPAC and HVA were greater in endorphin-treated than in saline-treated animals, supporting the concept that β-endorphin increases striatal dopamine turnover. β-endorphin increased the rate of decline in striatal dopamine concentration following synthesis inhibition with α-methyltyrosine, further suggesting that endorphin increases striatal dopamine turnover. β-endorphin and probenecid interacted competitively to decrease the effects of each other to increase striatal HVA. Naloxone prevented the effect of endorphin to decrease the HVA response to probenecid. Thus, probenecid cannot be used to assess the effects of endorphin on striatal dopamine turnover. If β-endorphin acts presynaptically to decrease dopamine release in striatum, the increases in striatal DOPAC and HVA probably represent a compensatory attempt to increase dopamine synthesis. Although turnover of dopamine to its metabolites is increased, dopamine release may be suppressed by β-endorphin.     

Mutants of Cellulomonas which produce increased levels of β-glucosidase

Summary Mutants have been isolated from a strain of Cellulomonas which are capable of producing up to 26-fold higher levels of -glucosidase than the parent under certain growth conditions.     

The production of 6-aminopenicillanic acid by a multistage tubular reactor packed with immobilized penicillin amidase

A theoretical model equation was derived to find the correlation between the conversion and the amount of immobilized penicillin amidase in column. The theoretical values of the conversion were predicted form this correlation and compared with experimental results. It was observed in a column reactor that the pH drop along the column path was linear versus the enzyme loading and that the enzyme activity was also linearly dependent on pH up to 8.0. In order to diminish the effect of pH drop, a continuous two-stage plug-flow reactor (PFR) with pH adjustment between the two columns was used was used in the experiments, and two- and three-stage PFRs were simulated by computer. In the case of the two-stage PFR, the maximum productivity was demonstrated experimentally and theoretically as well. when an equal amount of the immobilized enzyme was packed in both columns. It was also predicted in the tree-stage PFR system that the optimal distributions of enzyme loading in three columns were found to be 1:1:1. It was demonstrated that the increased number of reactors in series could enhance the level of the maximum productivity with a given amount of enzyme loading.     

Nucleotide sequence and characterization of the sfs1 gene: sfs1 is involved in CRP*-dependent mal gene expression in Escherichia coli.

We have cloned at least 12 different Escherichia coli genes which enable strain MK2001 to use maltose. The genes were designated sfs1 through sfs12 (sugar fermentation stimulation). Previously, one (sfs7) of them was mapped at 65 min on the E. coli chromosome and identified as nlp, which has high homology to repressor protein (Ner) of Mu phage, which contains a putative DNA binding region (Y.-L. Choi, T. Nishida, M. Kawamukai, R. Utsumi, H. Sakai, and T. Komano, J. Bacteriol. 171:5222-5225, 1989). In this study, another gene (sfs1) located at 3.5 min was newly found and analyzed. The nucleotide sequence of sfs1 encoded a protein of 234 amino acids (molecular mass, 26,227 Da) which also has a putative DNA binding domain. Overexpression of the sfs1 gene in MK2001 resulted in a 10-fold increase of amylomaltase, which was still dependent on MalT. These results suggest that Sfs1 could be a new regulatory factor involved in maltose metabolism.     

Sandwich capture ELISA by a murine monoclonal antibody against a genus-specific LPS epitope for the detection of different common serotypes of salmonellas.

A sandwich capture ELISA based on a murine monoclonal antibody against a genus-specific epitope in the outer core region of the Salmonella lipopolysaccharide is described for the detection of different common serotypes of salmonellas. Four h broth cultures of seven standard and 24 wild strains of salmonellas were all detected by the capture ELISA while overnight broth cultures of 21 non-salmonella standard strains were all negative. The capture ELISA detected 1 ng/ml of Ra lipopolysaccharide, 10(6)/ml of a smooth wild strain of Salm. typhimurium, and 1120 cells of Salm. heidelberg after enrichment culture for 4 h.