Silva Laport Marinella, da Silva Marilene Ramos, Costa Silva Carla, do Carmo de Freire Bastos Maria, Giambiagi-deMarval Marcia
Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, CCS, Bloco I, Cidade Universitária 21491-590, Rio de Janeiro, RJ, Brazil.
Curr Microbiol. 2003 May;46(5):313-7. doi: 10.1007/s00284-002-3828-0.
We have characterized the heat-shock response of the nosocomial pathogen Enterococcus faecium. The growth of E. faecium cells was analyzed at different temperatures; little growth was observed at 50 degrees C, and no growth at 52 degrees C or 55 degrees C. In agreement, a marked decrease of general protein synthesis was observed at 52 degrees C, and very light synthesis was detected at 55 degrees C. The heat resistance of E. faecium cells was analyzed by measuring the survival at temperatures higher than 52 degrees C and, after 2 h of incubation, viable cells were still observed at 70 degrees C. By Western blot analysis, two heat-induced proteins were identified as GroEL (65 kDa) and DnaK (75 kDa). Only one isoform for either GroEL or DnaK was found. The gene expression of these heat-shock proteins was also analyzed by pulsed-labeled experiments. The heat-induced proteins showed an increased rate of synthesis during the first 5 min, reaching the highest level of induction after 10 min and returning to the steady-state level after 20 min of heat treatment.
我们已对医院病原体粪肠球菌的热休克反应进行了表征。在不同温度下分析了粪肠球菌细胞的生长情况；在50℃时观察到生长极少，在52℃或55℃时未观察到生长。与此一致的是，在52℃时观察到总蛋白质合成显著下降，在55℃时检测到非常微弱的合成。通过测量在高于52℃的温度下的存活率来分析粪肠球菌细胞的耐热性，并且在孵育2小时后，在70℃仍观察到活细胞。通过蛋白质印迹分析，鉴定出两种热诱导蛋白为GroEL（65 kDa）和DnaK（75 kDa）。仅发现了GroEL或DnaK的一种同工型。还通过脉冲标记实验分析了这些热休克蛋白的基因表达。热诱导蛋白在最初5分钟内合成速率增加，在10分钟后达到最高诱导水平，并在热处理20分钟后恢复到稳态水平。
