Mycobacteria Research Laboratories, Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA.
J Bacteriol. 2011 Oct;193(20):5802-9. doi: 10.1128/JB.05299-11. Epub 2011 Aug 12.
Lipoarabinomannan (LAM) is a structurally heterogeneous amphipathic lipoglycan present in Mycobacterium spp. and other actinomycetes, which constitutes a major component of the cell wall and exhibits a wide spectrum of immunomodulatory effects. Analysis of Mycobacterium smegmatis subcellular fractions and spheroplasts showed that LAM and lipomannan (LM) were primarily found in a cell wall-enriched subcellular fraction and correlated with the presence (or absence) of the mycolic acids in spheroplast preparations, suggesting that LAM and LM are primarily associated with the putative outer membrane of mycobacteria. During the course of these studies significant changes in the LAM/LM content of the cell wall were noted relative to the age of the culture. The LAM content of the M. smegmatis cell wall was dramatically reduced as the bacilli approached stationary phase, whereas LM, mycolic acid, and arabinogalactan content appeared to be unchanged. In addition, cell morphology and acid-fast staining characteristics showed variations with growth phase of the bacteria. In the logarithmic phase, the bacteria were found to be classic rod-shaped acid-fast bacilli, while in the stationary phase M. smegmatis lost the characteristic rod shape and developed a punctate acid-fast staining pattern with carbolfuchsin. The number of viable bacteria was independent of LAM content and phenotype. Taken together, the results presented here suggest that LAM is primarily localized with the mycolic acids in the cell wall and that the cellular concentration of LAM in M. smegmatis is selectively modulated with the growth phase.
阿拉伯半乳聚糖甘露聚糖 (LAM) 是分枝杆菌属和其他放线菌中存在的一种结构不均一的两亲性糖脂，它构成细胞壁的主要成分，并表现出广泛的免疫调节作用。分析分枝杆菌属的亚细胞部分和原生质球显示，LAM 和脂阿拉伯甘露聚糖（LM）主要存在于富含细胞壁的亚细胞部分，与原生质球制剂中存在（或不存在）的分枝菌酸有关，表明 LAM 和 LM 主要与分枝杆菌的假定外膜相关。在这些研究过程中，相对于培养物的年龄，细胞壁中 LAM/LM 的含量发生了显著变化。分枝杆菌细胞壁中 LAM 的含量随着细菌接近静止期而显著降低，而 LM、分枝菌酸和阿拉伯半乳聚糖的含量似乎没有变化。此外，细胞形态和抗酸性染色特征随细菌生长阶段而变化。在对数期，细菌被发现为典型的杆状抗酸杆菌，而在静止期，分枝杆菌失去了特征性的杆状形状，并在石炭酸复红中呈现点状抗酸性染色模式。活菌数量与 LAM 含量和表型无关。总之，这里提出的结果表明，LAM 主要定位于细胞壁中的分枝菌酸中，分枝杆菌属中 LAM 的细胞浓度随生长阶段选择性调节。
