Saito Holly E, Harp John R, Fozo Elizabeth M
Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA.
Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
Appl Environ Microbiol. 2014 Oct;80(20):6527-38. doi: 10.1128/AEM.02044-14. Epub 2014 Aug 15.
Enterococcus faecalis is a commensal bacterium of the mammalian intestine that can persist in soil and aquatic systems and can be a nosocomial pathogen to humans. It employs multiple stress adaptation strategies in order to survive such a wide range of environments. Within this study, we sought to elucidate whether membrane fatty acid composition changes are an important component for stress adaptation. We noted that E. faecalis OG1RF was capable of changing its membrane composition depending upon growth phase and temperature. The organism also readily incorporated fatty acids from bile, serum, and medium supplemented with individual fatty acids, often dramatically changing the membrane composition such that a single fatty acid was predominant. Growth in either low levels of bile or specific individual fatty acids was found to protect the organism from membrane challenges such as high bile exposure. In particular, we observed that when grown in low levels of bile, serum, or the host-derived fatty acids oleic acid and linoleic acid, E. faecalis was better able to survive the antibiotic daptomycin. Interestingly, the degree of membrane saturation did not appear to be important for protection from the stressors examined here; instead, it appears that a specific fatty acid or combination of fatty acids is critical for stress resistance.
粪肠球菌是哺乳动物肠道中的一种共生细菌，它能够在土壤和水生系统中存活，并且可能成为人类的医院病原体。为了在如此广泛的环境中生存，它采用了多种应激适应策略。在本研究中，我们试图阐明膜脂肪酸组成的变化是否是应激适应的重要组成部分。我们注意到，粪肠球菌OG1RF能够根据生长阶段和温度改变其膜组成。该生物体还能轻易地从胆汁、血清和添加了单个脂肪酸的培养基中摄取脂肪酸，常常会显著改变膜组成，使单一脂肪酸占主导地位。发现在低水平胆汁或特定单个脂肪酸中生长能保护该生物体免受诸如高胆汁暴露等膜挑战。特别是，我们观察到，当在低水平胆汁、血清或宿主来源的脂肪酸油酸和亚油酸中生长时，粪肠球菌更能耐受抗生素达托霉素。有趣的是，膜的饱和度对于抵御此处所研究的应激源似乎并不重要；相反，似乎特定的一种脂肪酸或脂肪酸组合对于抗应激至关重要。
