Adams Hannah M, Joyce Luke R, Guan Ziqiang, Akins Ronda L, Palmer Kelli L
Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA.
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, USA.
Antimicrob Agents Chemother. 2017 Apr 24;61(5). doi: 10.1128/AAC.02552-16. Print 2017 May.
Synthesis and integrity of the cytoplasmic membrane are fundamental to cellular life. Experimental evolution studies have hinted at unique physiology in the Gram-positive bacteria and These organisms commonly cause bacteremia and infectious endocarditis (IE) but are rarely investigated in mechanistic studies of physiology and evolution. Unlike in other Gram-positive pathogens, high-level (MIC ≥ 256 μg/ml) daptomycin resistance rapidly emerges in and after a single drug exposure. In this study, we found that inactivating mutations in are associated with high-level daptomycin resistance in and IE isolates. This is surprising given that is an essential gene for life in commonly studied model organisms. CdsA is the enzyme responsible for the synthesis of CDP-diacylglycerol, a key intermediate for the biosynthesis of all major phospholipids in prokaryotes and most anionic phospholipids in eukaryotes. Lipidomic analysis by liquid chromatography-mass spectrometry (LC-MS) showed that daptomycin-resistant strains have an accumulation of phosphatidic acid and completely lack phosphatidylglycerol and cardiolipin, two major anionic phospholipids in wild-type strains, confirming the loss of function of CdsA in the daptomycin-resistant strains. To our knowledge, these daptomycin-resistant streptococci represent the first model organisms whose viability is CdsA independent. The distinct membrane compositions resulting from the inactivation of not only provide novel insights into the mechanisms of daptomycin resistance but also offer unique opportunities to study the physiological functions of major anionic phospholipids in bacteria.
细胞质膜的合成与完整性是细胞生命的基础。实验进化研究暗示革兰氏阳性菌具有独特的生理学特性，并且这些微生物通常会引起菌血症和感染性心内膜炎（IE），但在生理学和进化的机制研究中很少被研究。与其他革兰氏阳性病原体不同，在单次药物暴露后，[具体细菌名称]中会迅速出现高水平（MIC≥256μg/ml）的达托霉素耐药性。在本研究中，我们发现[具体基因名称]的失活突变与[具体细菌名称]和IE分离株中的高水平达托霉素耐药性相关。鉴于[具体基因名称]在常用的模式生物中是生命必需基因，这一发现令人惊讶。CdsA是负责合成CDP - 二酰甘油的酶，CDP - 二酰甘油是原核生物中所有主要磷脂以及真核生物中大多数阴离子磷脂生物合成的关键中间体。通过液相色谱 - 质谱联用（LC - MS）进行的脂质组分析表明，耐达托霉素菌株中存在磷脂酸积累，并且完全缺乏野生型菌株中的两种主要阴离子磷脂——磷脂酰甘油和心磷脂，这证实了耐达托霉素菌株中CdsA功能的丧失。据我们所知，这些耐达托霉素的链球菌代表了首批其生存能力不依赖CdsA的模式生物。[具体基因名称]失活导致的独特膜组成不仅为达托霉素耐药机制提供了新的见解，也为研究细菌中主要阴离子磷脂的生理功能提供了独特的机会。
