RESUMO
Beta-lactams are the most widely used antibiotics. One of the principle mechanisms for Gram-negative bacteria to resist β-lactams is by producing β-lactamases that degrade β-lactams. This review highlights two regulatory mechanisms for inducing β-lactamase in Gram-negative bacteria. In the ampR-ampC paradigm, the induction of β-lactamase is intimately linked to peptidoglycan recycling. AmpR, a LysR-type transcriptional regulator, plays a central role in regulating expression of β-lactamase. Recent studies found that two-component signal transduction pathway is activated by β-lactams, which in turn induces the expression of β-lactamase. Finally, we discussed the future research directions in β-lactam resistance in Gram-negative bacteria.
RESUMO
A zinc chloride and ethionine resistant mutant 0 5Eth400 5 was o btained from its parent strain Saccharomyces cerevisiae 346 by UV and 60 Co ? ray tr e atment and rational screening The glutathione productivity of the mutant reach e d 165 96mg/L by flask culture, which was 350% higher than the parent strain, an d the glutathione content in the dried cells reached 19 76mg/g, which was 318 6% higher than the parent strain A desecend of only 10 7% in the glutathione yie ld of the mutant was observed after ten times of subculture Therefore, the obtai ned mutant is stable strain that is worthwhile to be studied further
RESUMO
The better conditions for flask fermentation of Grifola frondosa are:QF medium.25℃.pH4 5 filled volume 60mL/500mL flask.rotated speed 100rpm.When 0 4%CMC is added to medium,the growing point of mycelia can increase and the biomass is rised.Scale\|up test has done in 10 litre airlift bioreactor.The rate of biotransformation between biomass and original sugar or between biomass and consuming sugar is over 24% or up to 435%.In mycelium the polysaccharide content is 10 2%.In culture fluid the polysaccharide content is 1 38%.