PubMed · 13918092
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T V SUBBAIAH, J B SELKON, A L BHATIA, S RADHAKRISHNA, D A MITCHISON. 1962. Catalase-enriched medium.. https://doi.org/10.1164/arrd.1962.85.1.133
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The catalase gene katA of Lactobacillus sakei SR911 was cloned and expressed in Escherichia coli UM2 and Lactobacillus plantarum TISTR850 under strong lactococcal promoter P59 in E. coli-lactococcus expression vector pIL1020. The L. plantarum TISTR850 is a catalase-deficient strain isolated from local fermented meat product. The recombinant L. plantarum TISTR850 was shown to decompose hydrogen peroxide, and catalase activity approximately three times higher that of natural catalase-producing strain L. sakei SR911. The recombinant protein was also detected by in situ activity staining of the catalase enzyme. The recombinant L. plantarum TISTR850 did not accumulate hydrogen peroxide under glucose-limited aerobic conditions and remained viable after 60 h of incubation. The recombinant and host strain L. plantarum TISTR850 were used as starter cultures in the fermented meat product, and lipid oxidation was monitored over a 7-day storage at 20 degrees C determined as thiobarbituric acid-reactive substances (TBARS) value. The lipid oxidation level in the fermented meat product seeded with the catalase genetically modified starter culture L. plantarum TISTR850 was significantly lower than that of the natural catalase-deficient strain.
Sinistrin, as inulin, is widely used as a marker for renal function testing. A reliable and accurate method with a simple sample preparation for the quantitative determination of sinistrin would be of advantage. We developed a high-performance liquid chromatography (HPLC)-based method with electrochemical detection for the quantitative measurement of sinistrin in serum and plasma. Sample preparation is easy and includes enzymatic removal of glucose, deproteinization, acid hydrolysis of sinistrin, and HPLC separation of fructose. The recovery of sinistrin from serum is the same as that from water and is near 100%. The method presented has a linear range up to 500 mg/L. The results from our method are in agreement with a fully enzymatic quantification (regression coefficient 1.01, coefficient of variation 0.97). Sinistrin concentrations in aqueous solutions can be measured down to 2mg/L with a coefficient of variation of 5.7%. Quantification in serum is primarily limited by its physiological fructose content. The sensitivity of the described method is sufficient for its use in renal function testing. We describe a method for quantification of sinistrin which allows accurate measurements especially at low concentrations and low sample volumes. This laboratory method may be used for obtaining sinistrin pharmacokinetics in renal function testing.
The results reported herein indicate that the ultraviolet-A (UVA) radiation-induced effects in Escherichia coli depend on its growth phase. Stationary-phase cells recover faster from a sub-lethal UVA exposure and have a higher resistance to lethal effect of the radiation than exponential growing cells. Although pre-incubation in spent medium supernatant increased the resistance of log-phase cells to lethal UVA effects, this pre-treatment considerably prolonged the duration of the radioinduced sub-lethal growth delay. The aim of the present study was to investigate the effect exerted by the E. coli conditioned media and evaluate the influence of nutritional stress, hydrogen peroxide and acetate. Pre-incubated in conditioned medium, cells in exponential growth phase were irradiated and the induced effects were compared with those found when catalase, high culture densities and acetate were employed. Unexpectedly, the duration of the growth delay in cells submitted to these treatments was shortened in comparison with control cells incubated in conditioned medium with no modifications. Lengthening of the growth delay was mimicked when exponentially growing cells were incubated in fresh medium supplied with 5 microM H(2)O(2). The effects of spent medium on wild type and rpoS mutant strains were similar, indicating that this response is independent of RpoS controlled functions. We assumed that an oxidative component of the spent medium, probably H(2)O(2), could be involved in the observed phenomenon. This effect is specific of E. coli and independent of rpoS.