Abstract

Sericins are derived from the outer layer of silk thread proteins of the common silkworm (Bombyx mori) and act as a glue to fix fibers of the developing cocoon. Although sericin has potential uses in various fields, including tissue engineering and the development of cosmetics, biological applications of intact sericin have yet to be identified. We previously developed transgenic silkworms that produce cocoons solely composed of sericin, from which we can readily prepare a solution of intact sericin. Here we report the effects of intact sericin on the proliferation of bacteria. The intact sericin does not kill bacteria, but colony size of Escherichia coli on culture media was reduced by up to 90% when cultured in the presence of intact sericin. In addition, treatment of intact sericin reduced colony size of Salmonella enterica, indicating a potential inhibitory effect of intact sericin on growth in Gram-negative bacteria. However, Gram-positive bacteria, including Staphylococcus aureus and Bacillus subtilis, were not affected by intact sericin. Thus, our results indicate that the cell wall structure of different bacteria may influence their sensitivity to the inhibitory effects of sericin.

摘要

丝胶蛋白衍生自普通家蚕（Bombyx mori）的丝线蛋白外层，并起胶水的作用，固定发育中茧的纤维。尽管丝胶蛋白在各种领域具有潜在用途，包括组织工程和化妆品开发，但完整的丝胶蛋白在生物学上的应用尚待确定。我们以前曾开发过转基因蚕，它们可生产仅由丝胶蛋白组成的茧，因此我们可以很容易地制备出完整的丝胶蛋白溶液。在这里，我们报告完整的丝胶蛋白对细菌增殖的影响。完整的丝胶蛋白不会杀死细菌，但会杀死大肠杆菌的菌落大小在完整的鞘胶存在下进行培养时，培养基上的细菌减少高达90％。此外，完整丝胶蛋白的治疗可减少肠道沙门氏菌的菌落大小，表明完整丝胶蛋白对革兰氏阴性菌的生长具有潜在的抑制作用。但是，包括金黄色葡萄球菌和枯草芽孢杆菌在内的革兰氏阳性细菌不受完整的丝胶蛋白的影响。因此，我们的结果表明，不同细菌的细胞壁结构可能会影响其对丝胶蛋白抑制作用的敏感性。