Chaput Catherine, Labigne Agnès, Boneca Ivo G
Unité de Pathogénie Bactérienne des Muqueuses, Department of Microbiology, Institut Pasteur, 28 Rue du Dr. Roux, 75724 Paris cedex 15, France.
J Bacteriol. 2007 Jan;189(2):422-9. doi: 10.1128/JB.01270-06. Epub 2006 Nov 3.
Peptidoglycan (PG) is a cell wall heteropolymer that is essential for cell integrity. PG hydrolases participate in correct assembly of the PG layer and have been shown to be required for cell division, cell daughter separation, and maintenance of bacterial morphology. In silico analysis of the Helicobacter pylori genome resulted in identification of three potential hydrolases, Slt, MltD, and AmiA. This study was aimed at determining the roles of the putative lytic transglycosylases, Slt and MltD, in H. pylori morphology, growth, and PG metabolism. Strain 26695 single mutants were constructed using a nonpolar kanamycin cassette. The slt and mltD mutants formed normal bacillary and coccoid bacteria in the exponential and stationary phases, respectively. The slt and mltD mutants had growth rates comparable to the growth rate of the parental strain. However, the mltD mutant exhibited enhanced survival in the stationary phase compared to the wild type or the slt mutant. PG was purified from exponentially growing bacteria and from bacteria in the stationary phase, and its muropeptide composition was analyzed by high-pressure liquid chromatography. This analysis revealed changes in the muropeptide composition indicating that MltD and Slt have lytic transglycosylase activities. Glycan strand analysis suggested that Slt and MltD have exo and endo types of lytic transglycosylase activity, indicating that Slt is involved mainly in PG turnover and MltD is involved mainly in rearrangement of the PG layer. In this study, we determined the distinct roles of the lytic transglycosylases Slt and MltD in PG metabolism.
肽聚糖（PG）是一种对细胞完整性至关重要的细胞壁杂聚物。PG水解酶参与PG层的正确组装，并且已被证明是细胞分裂、子细胞分离和细菌形态维持所必需的。对幽门螺杆菌基因组的计算机分析鉴定出三种潜在的水解酶，即Slt、MltD和AmiA。本研究旨在确定推定的溶菌转糖基酶Slt和MltD在幽门螺杆菌形态、生长和PG代谢中的作用。使用非极性卡那霉素盒构建了26695菌株单突变体。slt和mltD突变体在指数期和稳定期分别形成正常的杆菌和球菌。slt和mltD突变体的生长速率与亲本菌株的生长速率相当。然而，与野生型或slt突变体相比，mltD突变体在稳定期表现出更高的存活率。从指数生长期细菌和稳定期细菌中纯化PG，并通过高压液相色谱分析其胞壁肽组成。该分析揭示了胞壁肽组成的变化，表明MltD和Slt具有溶菌转糖基酶活性。聚糖链分析表明，Slt和MltD具有外切型和内切型溶菌转糖基酶活性，表明Slt主要参与PG周转，而MltD主要参与PG层的重排。在本研究中，我们确定了溶菌转糖基酶Slt和MltD在PG代谢中的不同作用。
