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首页> 外文期刊>Journal of bacteriology >Cloning and characterization of a gene affecting the methicillin resistance level and the autolysis rate in Staphylococcus aureus.
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Cloning and characterization of a gene affecting the methicillin resistance level and the autolysis rate in Staphylococcus aureus.

机译：影响金黄色葡萄球菌耐甲氧西林水平和自溶率的基因的克隆和鉴定。

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Tn918 mutagenesis of a high-level methicillin-resistant Staphylococcus aureus (methicillin MIC, 800 micrograms/ml) led to the isolation of a low-resistance mutant. The Tn918 insert was transferred back to the parent to produce strain SRM563 (methicillin MIC, 12.5 micrograms/ml), which showed heterogeneous resistance. Twenty-two clinical isolates of methicillin-resistant S. aureus were transformed with DNA of SRM563. In the transformants of most strains, instances of reduced resistance were observed with concomitant increases of autolysis rate induced by Triton X-100 and were generally more profound in high-resistance strains. Two transformants exhibited a decrease of the autolysis rate and little reduction of resistance. In the transformant of methicillin-susceptible strain RN2677, an increase of the autolysis rate and little reduction of resistance were observed. The production of low-affinity penicillin-binding protein (PBP2') did not significantly decrease in the mutants. Insertion of Tn918 occurred within the 3'-terminal region of a novel gene designated llm, which was cloned and sequenced. RNA blot analysis demonstrated that the gene was transcribed. The encoded protein was composed of 351 amino acid residues with a molecular weight of 38,512 and was hydrophobic, suggesting its location on the membrane. The gene was detected by PCR in all S. aureus strains tested but not in the other 26 staphylococcal species. Comparison of the 3'-terminal sequences of the gene among several S. aureus strains showed that, whereas nucleotide substitutions occurred at the third position in seven of eight 3'-terminal codons, only C-terminal amino acid variation of glutamate or aspartate was observed.
机译：高水平耐甲氧西林金黄色葡萄球菌（甲氧西林MIC，800微克/毫升）的Tn918诱变导致分离出低抗性突变体。将Tn918插入片段转移回亲本，以产生菌株SRM563（甲氧西林MIC，12.5微克/毫升），该菌株显示出异种抗性。用SRM563的DNA转化了22株耐甲氧西林金黄色葡萄球菌的临床分离株。在大多数菌株的转化株中，观察到抗性降低的情况，并伴随着由Triton X-100诱导的自溶速率的提高，并且在高抗性菌株中通常更为明显。两个转化体表现出自溶速率的降低和抗性的降低。在对甲氧西林敏感的菌株RN2677的转化株中，观察到自溶速率的提高和耐药性的降低。低亲和力青霉素结合蛋白（PBP2'）的生产并没有明显减少突变体中。 Tn918的插入发生在一个名为llm的新基因的3'末端区域，该基因被克隆并测序。 RNA印迹分析表明该基因已被转录。编码的蛋白质由351个氨基酸残基组成，分子量38,512，具有疏水性，表明其在膜上的位置。通过PCR在所有测试的金黄色葡萄球菌菌株中检​​测到该基因，但在其他26种葡萄球菌物种中未检测到。比较几个金黄色葡萄球菌菌株中该基因的3'末端序列，结果表明，尽管核苷酸取代发生在八个3'末端密码子中的七个的第三位，但谷氨酸或天冬氨酸的C末端氨基酸变异却是观测到的。

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