ULTRASTRUCTURE AND CHEMICAL-COMPOSITION OF THE SHEATH OF LEPTOTHRIX-DISCOPHORA SP-6
ULTRASTRUCTURE AND CHEMICAL-COMPOSITION OF THE SHEATH OF LEPTOTHRIX-DISCOPHORA SP-6
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DOI：
10.1128/jb.175.24.7808-7818.1993
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发表时间：
1993-12-01
影响因子：
3.2
通讯作者：
GHIORSE, WC
中科院分区：
文献类型：
--
作者：
EMERSON, D;GHIORSE, WC
薄切片和金属阴影标本的光学显微镜和透射电子显微镜显示，盘状纤丝菌SP-6（ATCC 51168）的鞘是一种管状的细胞外聚合物结构，由直径为6.5 nm的原纤维的凝聚织物组成，其下是一个更弥散的外囊层。在薄切片中，观察到与内鞘层接触的外膜桥表明鞘织物附着在革兰氏阴性细胞壁的外层。荚膜聚合物表现出对阳离子胶体铁和聚阳离子铁蛋白的亲和力，表明它们携带负电荷。通过用溶菌酶、EDTA和N-月桂酰肌氨酸（Sarkosyl）或十二烷基硫酸钠（SDS）的混合物处理来分离无细胞鞘。肌氨酰和SDS分离的鞘在显微镜下外观无法区分。然而，锰氧化活性Sarkosyl隔离鞘比SDS隔离鞘更稳定。Sarkosyl分离的鞘也含有更多的2-酮基-3-脱氧辛酸和更多的外膜蛋白比SDS分离的鞘。洗涤剂分离的鞘的烘箱干燥质量代表SP-6培养物的总烘箱干燥生物质的约9%;烘箱干燥的鞘含有38%C、6.9%N、6%H和2.1%S以及约34至35%碳水化合物（多糖）、23至25%蛋白质、8%脂质和4%无机灰分。气液色谱显示，该多糖是糖醛酸（葡萄糖醛酸、半乳糖醛酸和甘露糖醛酸以及至少一种其他未鉴定的糖醛酸）和氨基糖（半乳糖胺）的约1：1混合物。未检出中性糖。氨基酸分析表明，鞘蛋白富含半胱氨酸（6摩尔%）。鞘蛋白中的半胱氨酸残基可能为二硫键提供巯基，这在维持鞘的结构完整性方面发挥着重要作用（D.爱默生和W. C. Ghiorse，J. Bacteriol. 175：7819-7827，1993）。
Light microscopy and transmission electron microscopy of thin sections and metal-shadowed specimens showed that the sheath of Leptothrix discophora SP-6 (ATCC 51168) is a tube-like extracellular polymeric structure consisting of a condensed fabric of 6.5-nm-diameter fibrils underlying a more diffuse outer capsular layer. In thin sections, outer membrane bridges seen to contact the inner sheath layer suggested that the sheath fabric was attached to the outer layer of the gram-negative cell wall. The capsular polymers showed an affinity for cationic colloidal iron and polycationic ferritin, indicating that they carry a negative charge. Cell-free sheaths were isolated by treatment with a mixture of lysozyme, EDTA, and N-lauroylsarcosine (Sarkosyl) or sodium dodecyl sulfate (SDS). Both Sarkosyl- and SDS-isolated sheaths were indistinguishable in microscopic appearance. However, the Mn-oxidizing activity of Sarkosyl-isolated sheaths was more stable than that of SDS-isolated sheaths. The Sarkosyl-isolated sheaths also contained more 2-keto-3-deoxyoctanoic acid and more outer membrane protein than SDS-isolated sheaths. The oven-dried mass of detergent-isolated sheaths represented approximately 9% of the total oven-dried biomass of SP-6 cultures; the oven-dried sheaths contained 38% C, 6.9% N, 6% H, and 2.1% S and approximately 34 to 35% carbohydrate (polysaccharide), 23 to 25% protein, 8% lipid, and 4% inorganic ash. Gas-liquid chromatography showed that the polysaccharide was an approximately 1:1 mixture of uronic acids (glucuronic, galacturonic, and mannuronic acids and at least one other unidentified uronic acid) and an amino sugar (galactosamine). Neutral sugars were not detected. Amino acid analysis showed that sheath proteins were enriched in cysteine (6 mol%). The cysteine residues in the sheath proteins probably provide sulfhydryls for disulfide bonds that play an important role in maintaining the structural integrity of the sheath (D. Emerson and W. C. Ghiorse, J. Bacteriol. 175:7819-7827, 1993).