Department of Endodontics and Operative Dentistry, Ninth People's Hospital, Shanghai Key Laboratory of Stomatology, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Shanghai, China.
Arch Oral Biol. 2012 Jan;57(1):10-4. doi: 10.1016/j.archoralbio.2011.06.011. Epub 2011 Jul 8.
The aim of this study was to compare the membrane fatty acid profile and expression of the fabM gene in a fluoride-resistant Streptococcus mutans strain with those of its wild-type counterpart. Additionally, we aimed to investigate whether mutations were present in the fabM gene of the fluoride-resistant strain.
A fluoride-resistant strain of S. mutans was obtained by step-by-step induction in vitro. The fluoride-resistant strain and its wild-type counterpart were grown anaerobically in a brain heart infusion broth, harvested and resuspended in a salt solution for an acid survival assay and a pH-drop experiment. The membrane fatty acid profile was determined by gas chromatography-mass spectrometry. Expression of the fabM gene was quantified by real-time PCR. The fabM gene was also sequenced.
The ability of the fluoride-resistant strain to resist acid stress was greater than that of the wild-type strain. A significant difference in the amount of long-chain monounsaturated fatty acids between the fluoride-resistant strain and the wild-type strain was detected in acidic condition (P<0.01). In addition, the level of fabM mRNA in the fluoride-resistant strain was significantly higher than that of the wild-type strain in the acidic condition as well (P<0.01). However, the sequence of the fabM gene from the fluoride-resistant strain was 100% homologous with that from the wild-type strain.
The membrane fatty acid profile and expression of the fabM gene in the fluoride-resistant strain were altered compared to the wild-type strain in acidic conditions, but no differences were found in the sequence of the fabM gene.
本研究旨在比较耐氟变形链球菌株与野生型菌株的膜脂肪酸谱和 fabM 基因表达，并研究耐氟菌株 fabM 基因是否存在突变。
通过体外逐步诱导获得耐氟变形链球菌株。将耐氟菌株及其野生型菌株在脑心浸液肉汤中进行厌氧培养，收获并悬浮在盐溶液中进行酸存活试验和 pH 值下降试验。采用气相色谱-质谱法测定膜脂肪酸谱。通过实时 PCR 定量 fabM 基因的表达。还对 fabM 基因进行了测序。
耐氟菌株抵抗酸应激的能力强于野生型菌株。在酸性条件下，耐氟菌株与野生型菌株之间长链单不饱和脂肪酸的含量存在显著差异（P<0.01）。此外，在酸性条件下，耐氟菌株 fabM mRNA 的水平也明显高于野生型菌株（P<0.01）。然而，耐氟菌株 fabM 基因的序列与野生型菌株 100%同源。
与野生型菌株相比，耐氟菌株在酸性条件下的膜脂肪酸谱和 fabM 基因表达发生了改变，但 fabM 基因的序列没有差异。
