Hyper‐production of α‐amylase from agro‐residual medium with high‐glucose in SSF using catabolite derepressed Bacillus subtilis KCC103

In Bacillus subtilis KCC103, α‐amylase is hyper‐produced and α‐amylase synthesis is not subject to catabolite repression. The α‐amylase was produced from KCC103 by solid‐state fermentation (SSF) using agro‐residues and oil cakes as growth substrates. The KCC103 was also tested for its resistance to repression by hyper level (>10% w/w) of glucose and xylose on α‐amylase production in SSF. Among growth media containing various combinations of agro‐residues, the medium with wheat bran and sunflower oil cake supported highest enzyme production (20700 IU (g dry wt)^–1). The α‐amylase production was enhanced (4.2 folds) by optimizing the growth substrate and the process parameters: the optimal conditions were wheat bran:sun flower oil cake ratio‐1:1 (w/w), substrate particle size‐500 μm, substrate to flask volume‐1:100 (w/v), initial substrate moisture content‐90% (v/w), inoculum size‐35%, initial medium pH‐7.0, growth temperature‐37 °C and cultivation time‐48 h. α‐Amylase production was further enhanced up to 1.7 folds when SSF was carried out using optimized medium supplemented with sugars or yeast extract (1% w/v) under optimized conditions. Supplementation of biomass sugars, glucose or xylose at 20% (w/w), did not repress the synthesis of α‐amylase showing the hyper‐tolerance of KCC103 to repression by simple sugars on α‐amylase production in SSF. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

应用尿素动力学模型评价血透病人透析充分性和营养状态的临床研究

应用尿素动力学参数时间平均尿素浓度（ＴＡＣｕｒｅａ）、整体尿素清除率（Ｋｔ／ｖ）、蛋白质分解代谢率（ＰＣＲ）对４２例维持性血液透析病人透析充分性及营养状态进行评价，并与临床结果进行比较，我们发现ＴＡＣｕｒｅａ和ＰＣＲ是反映血液透析长期充分与否的重要指标，Ｋｔ／Ｖ可直接反映单次透析效果，是调整析方案的最佳指标，在透析不充分的情况下，Ｋｔ／Ｖ对ＰＣＲ有着重要影响．     

Bacterial protein kinases that recognize tertiary rather than primary structure?

While all characterized eukaryotic protein kinases that phosphorylate hydroxy aminoacyl residues in proteins recognize primary structure, certain bacterial protein kinases are proving to recognize tertiary structure. It is proposed that thse latter enzymes evolved independently of the superfamily of the former protein kinases and that their modes of target protein recognition and action are entirely different.     

Sugar-responsive gene expression and the agr system are required for colony spreading in Staphylococcus aureus

Staphylococcus aureus spreads on soft agar surfaces, which is called “colony spreading”. Here, we report that the colony spreading in S. aureus was promoted by the addition of glucose to soft agar plates. Disruption of ccpA and hprK, which are involved in catabolite repression, decreased the colony spreading ability promoted by glucose. Deletion of the agr locus, a virulence regulatory element whose expression is activated by glucose in a ccpA-dependent manner, abolished the colony spreading promoted by glucose. Disruption of clpP and arlRS, which contributes to agr expression, also decreased glucose-promoted colony spreading. These findings suggest that S. aureus colony spreading requires the expression of agr, which is positively regulated by environmental carbon sources, and that virulence gene expression and colony spreading induced by agr are simultaneously activated in the S. aureus infectious process.     

The expression of a specific 2-deoxyglucose-6P phosphatase prevents catabolite repression mediated by 2-deoxyglucose in yeast

2-deoxyglucose (2-DOG), a non-metabolize analogue of glucose, is taken up by yeast using the same transporter(s) as glucose and is phosphorylated by hexokinases producing 2-deoxyglucose-6-P. We found that in DOG ^R yeasts, 2-DOG was not able to trigger glucose repression, even at concentrations of 0.5%. This result suggests that the specific 2-DOG-6P phosphatase, the enzyme responsible for the DOG ^R phenotype, may be involved in inhibiting the process of catabolite repression mediated by 2-DOG     

Inducible β-lactamase-mediated resistance to third-generation cephalosporins

The emergence of multiple resistance to β-lactam antimicrobial agents is a major problem in the treatment of patients infected with Enterobacteriaceae that characteristically produce inducible β-lactamases. Inducible and 'derepressed' AmpC β-lactamases are produced by Enterobacter spp., Citrobacter freundii, Serratia marcescens, Morganella morganii and Providencia spp. Resistance to broad-spectrum β-lactams has emerged in 16-44% of these strains from infections treated with one of the newer cephalosporins, even in combination with other antimicrobials. Multiply resistant organisms have spread widely both locally, within hospitals, and nationally. This trend has been shown to correlate closely with the extent of usage of some third-generation cephalosporins. These resistant strains, especially Enterobacter spp., are more regularly isolated from seriously ill patients (especially from respiratory sources), or in intensive care units and pose one of the greatest challenges to contemporary chemotherapy of infections in hospitalized patients. Zwitterionic fourth-generation cephalosporins combine the properties of rapid bacterial outer membrane penetration with high stability to AmpC β-lactamase with good affinity for the penicillin-binding proteins to achieve in vitro activity against AmpC-producing organisms, including the majority of strains highly resistant to ceftazidime and other earlier generation cephalosporins. These features have contributed to their clinical success in the therapy of infections caused by Enterobacter spp. with and without resistance to third-generation compounds. Other alternative agents for chemotherapy of infections due to AmpC β-lactamase-producing strains (inducible or derepressed expression) should also be considered e.g. carbapenems, aminoglycosides and fluoroquinolones.     

Saccharomyces cerevisiae strains sensitive to inorganic mercury

Summary Saccharomyces cerevisiae strains sensitive to inorganic mercury (Ono and Sakamoto 1985) did not grow well on the medium rich in glucose and poor in peptone. This growth inhibition, like growth inhibition caused by inorganic mercury, was relieved by exogenous tyrosine. Sugars such as fructose and mannose were as inhibitory as glucose, but glycerol was not at all. Galactose was inhibitory but not so much as glucose. Agal2l mutation (defective in galactose uptake) partly relieved growth inhibition caused by excess galactose. Moreover, it was found that some of revertants which gained ability to grow well in the presence of excess glucose were defective in the glucose uptake. From these observations, we conclude that growth inhibition of the inorganic mercury sensitive strains by excess sugar is a consequence of the catabolite regulation. In other words, the inorganic mercury sensitive strains are hyper-sensitive to the catabolite regulation due to the presence of theHGS2-1 allele.