Construction and secretory expression of beta-galactosidase gene from Lactobacillus bulgaricus in Lactococcus lactis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>This study is to examine the secretion effects of beta-galactosidase in Lactococcus lactis.</p><p><b>METHODS</b>The usp45 and beta-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant plasmid pMG36e-usp-lacZ. This recombinant plasmid was transformed into both Escherichia coli DH5alpha and L. lactis MG1363. The enzyme activity, gene sequencing, SDS-PAGE and hereditary stability were assessed and studied.</p><p><b>RESULTS</b>The lacZ gene inserted into plasmids pMG36e-usp-lacZ was 99.37% similar to the GenBank sequence, and SDS-PAGE revealed an evident idio-strap at 116 KDa between L. lactis MG1363/pMG36e-usp-lacZ in both supernatant and cell samples. Beta-Galactosidase activity measured 0.225 U/mL in L. lactis pMG36e-usp-lacZ transformants, and its secretion rate was 10%. The plasmid pMG36e-usp-lacZ appeared more stable in MG1363.</p><p><b>CONCLUSION</b>The authors concluded that these new recombinant bacteria well expressed and secreted beta-galactosidase, indicating that the beta-galactosidase expression system was successfully constructed, and this might provide a new solution for management of lactose intolerance specifically and promote the use of gene-modified organisms as part of the food-grade plasmid in general.</p>

Non-fusion and fusion expression of beta-galactosidase from Lactobacillus bulgaricus in Lactococcus lactis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To construct four recombinant Lactococcus lactis strains exhibiting high beta-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion.</p><p><b>METHODS</b>The gene fragments encoding beta-galactosidase from two strains of Lactobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the beta-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the beta-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the beta-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5 alpha and Lactococcus lactis subsp. lactis MG1363 and confirmed by determining beta-galactosidase activities.</p><p><b>RESULTS</b>The non-fusion expression plasmids showed a significantly higher beta-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the beta-galactosidase gene from Lactobacillus bulgaricus wch9901. The beta-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, beta-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate (27.1%) was observed when the culture medium contained 20 g/L of lactose.</p><p><b>CONCLUSION</b>Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus beta-galactosidase, and its translation product may introduce the enzyme secretion out of cells in special hosts.</p>

Comparative study on the resistance of Bacteriophage phi chi 174D, T4 and f2 to an iodophor in laboratory / 中华实验和临床病毒学杂志

<p><b>BACKGROUND</b>To screen for the most resistant bacteriophage as indicator in disinfection tests, the resistance of bacteriophage phi chi 174D, T4 and f2 to iodophor were observed in laboratory.</p><p><b>METHODS</b>The virucidal activity of iodophor against bacteriophage phi chi 174D, T4, and f2 were assessed by suspension test. The neutralizer is selected and appraised by testing with neutralizer. Bacteriophage phi chi 174D, T4, and f2 were detected and enumerated by the double-agar-layer plaque technique.</p><p><b>RESULTS</b>(1) With 500 mg/L of available iodine of iodophor solution, within a contact time of 40 min, or 750 mg/L, 10 min, or 1000 mg/L, 5 min, the reduction of bacteriophage phi chi 174D could achieve the "disinfection" level [log10 inactivation value (LIV) or log10 reduction value (LRV) of bacteriophage phi chi 174D (log10 No-log10 Nt) was > or = 4.00 log10]. (2) With 600 mg/L of available iodine of iodophor solution, within a contact time of 40 min, or 700 mg/L, 5 min, the reductions of bacteriophage T4 could achieve the "disinfection" level. (3) With 50 mg/L of available iodine of iodophor solution, within a contact time of 10 min, or 75 mg/L, 10 min, the reductions of bacteriophage f2 could achieve the "disinfection" level.</p><p><b>CONCLUSION</b>The order of resistance of the above three bacteriophages to iodophor from greatest to smallest is as follows: bacteriophage phi chi 174D greater than bacteriophage T4 > bacteriophage f2.</p>

Comparison on resistance of bacteriophages to sodium dichloroisocyanurate in laboratory / 中华预防医学杂志

<p><b>OBJECTIVE</b>To scan the most resistable bacteriophage as an indicator in disinfection tests, and to study the resistance of bacteriophage T4, Phichi 174D, and f2 to the sodium dichloroisocyanurate (NaDCC) in laboratory.</p><p><b>METHODS</b>The virucidal activity of NaDCC against bacteriophage T4, Phichi 174D, and f2 were assessed by suspension test. The neutralizer was selected and be appraised by test of neutralizer. Bacteriophage T4, Phichi 174D, and f2 were detected and enumerated by the double-agar-layer plaque technique.</p><p><b>RESULTS</b>(1) With 150 mg/L of available chlorine of NaDCC solution, within a contact time of 40 minutes, or 300 mg/L, 5 minutes, the reductions of bacteriophage T4 achieved the "disinfection" level [log(10) inactivation value or log(10) reduction value of bacteriophage T4 (log(10)No-log(10)Nt) > or = 4.00 log(10)]. (2) With 300 mg/L of available chlorine of NaDCC solution, within a contact time of 5 minutes, or 400 mg/L, 3 minutes, the reductions of bacteriophage Phichi 174D achieved the "disinfection" level. (3) With 2000 mg/L of available chlorine of NaDCC solution, within a contact time of 20 minutes, or 4000 mg/L, 5 minutes, the reductions of bacteriophage f2 might achieve the "disinfection" level.</p><p><b>CONCLUSION</b>The order of resistance of the above three bacteriophages to NaDCC from greatest to smallest is as follows: bacteriophage f2 > bacteriophage T4 > bacteriophage Phichi 174D.</p>

Comparison of susceptibilities of M. tuberculosis H37Ra and M. chelonei subsp. abscessus to disinfectants / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To determine the susceptibilities of M. tuberculosis H37Ra and M. chelonei subsp. absecessus to several frequently-used disinfectants and to evaluate the practicability of surrogating M. tuberculosis by the latter.</p><p><b>METHODS</b>A suspension quantitative bactericidal test was set up in accordance with Chinese Technique Standard for Disinfection to evaluate the susceptibility of each mycobacteria strain to each selected disinfectant. Killing log value was used as criterion in comparing the susceptibility to disinfectants between the two strains.</p><p><b>RESULTS</b>M. chelonei subsp. abscessus was more resistant to chlorine disinfectant than M. tuberculosis while the two strains were similarly resistant to iodophor disinfectant, peracetic acid, alcohol and glutaraldehyde disinfectant.</p><p><b>CONCLUSION</b>M. chelonei subsp. abscessus has the potential to surrogate M. tuberculosis in evaluating mycobactericidal efficacies of disinfectants.</p>