Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
J Biosci Bioeng. 2011 Jan;111(1):31-6. doi: 10.1016/j.jbiosc.2010.08.009. Epub 2010 Sep 19.
The toluene-degrading bacterium Acinetobacter sp. Tol 5 is highly adhesive through cell-surface nanofibers. Previously, we identified two morphologically distinct nanofibers on Tol 5 cells, namely, nonperitrichate anchor-like and peritrichate pilus-like nanofibers. In the present study, the application of improved electron microscopy techniques enabled discrimination of three distinct types of peritrichate nanofibers on Tol 5 cells. Interestingly, production of these nanofibers was affected by the available growth substrate. Thick, long, straight nanofibers a, which were present on cells grown on toluene, lactate, and ethanol, were not observed on cells grown on triacylglycerol (TAG). In contrast, cells grown on TAG were covered with long, curved nanofibers c, which only existed sparsely on cells grown on toluene, lactate, and ethanol. Thin, short, straight nanofibers b were found densely covering the margin of cells grown on all four growth substrates. SDS-PAGE of Tol 5 cell-surface proteins detected a protein of 17.5 kDa that was expressed at a high level on ethanol, but was undetectable on TAG. Conversely, a 26kDa protein was identified that was exclusively expressed on TAG, but was only faintly expressed by cells grown on the other substrates. Based on N-terminal amino acid sequences, the 17.5 and 26 kDa proteins were identified as the major subunits of type 1 and Fil pili, respectively, which are typical bacterionanofibers. From these results, we deduced that nanofibers a and c are type 1 and Fil pili, respectively. The adhesiveness of Tol 5 cells was low only when they were grown on TAG.
甲苯降解菌不动杆菌 Tol5 可通过细胞表面纳米纤维高度黏附。先前，我们在 Tol5 细胞上鉴定出两种形态不同的纳米纤维，即非周生锚定样和周生纤毛样纳米纤维。在本研究中，应用改良电子显微镜技术，能够区分 Tol5 细胞上三种不同类型的周生纳米纤维。有趣的是，这些纳米纤维的产生受可用生长底物的影响。在甲苯、乳酸盐和乙醇上生长的细胞上存在厚、长、直的纳米纤维 a，但在三酰基甘油 (TAG) 上生长的细胞上则观察不到。相反，在 TAG 上生长的细胞覆盖着长而弯曲的纳米纤维 c，这种纤维在甲苯、乳酸盐和乙醇上生长的细胞上稀疏存在。薄、短、直的纳米纤维 b 密集地覆盖在所有四种生长底物上生长的细胞边缘。 Tol5 细胞表面蛋白的 SDS-PAGE 检测到一种 17.5kDa 的蛋白，在乙醇中高表达，但在 TAG 中不可检测。相反，鉴定出一种 26kDa 的蛋白，它仅在 TAG 上表达，但在其他底物上生长的细胞中仅微弱表达。根据 N 末端氨基酸序列，17.5 和 26kDa 蛋白分别被鉴定为类型 1 和 Fil 菌毛的主要亚基，这是典型的细菌菌毛纳米纤维。根据这些结果，我们推断纳米纤维 a 和 c 分别是类型 1 和 Fil 菌毛。 Tol5 细胞仅在 TAG 上生长时，其黏附性较低。
