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HexSDF 对于新型糖脂的合成是必需的,这种糖脂介导艰难梭菌对达托霉素和杆菌肽的耐药性。

HexSDF Is Required for Synthesis of a Novel Glycolipid That Mediates Daptomycin and Bacitracin Resistance in C. difficile.

机构信息

Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.

Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, USA.

出版信息

mBio. 2023 Apr 25;14(2):e0339722. doi: 10.1128/mbio.03397-22. Epub 2023 Feb 14.

Abstract

Clostridioides difficile is a Gram-positive opportunistic pathogen responsible for 250,000 hospital-associated infections, 12,000 hospital-associated deaths, and $1 billion in medical costs in the United States each year. There has been recent interest in using a daptomycin analog, surotomycin, to treat C. difficile infections. Daptomycin interacts with phosphatidylglycerol and lipid II to disrupt the membrane and halt peptidoglycan synthesis. C. difficile has an unusual lipid membrane composition, as it has no phosphatidylserine or phosphatidylethanolamine, and ~50% of its membrane is composed of glycolipids, including the unique C. difficile lipid aminohexosyl-hexosyldiradylglycerol (HNHDRG). We identified a two-component system (TCS), HexRK, that is required for C. difficile resistance to daptomycin. Using transcriptome sequencing (RNA-seq), we found that HexRK regulates expression of , a three-gene operon of unknown function. Based on bioinformatic predictions, encodes a monogalactosyldiacylglycerol synthase, encodes a polysaccharide deacetylase, and encodes an MprF-like flippase. Deletion of leads to a 4-fold decrease in daptomycin MIC, and that deletion of leads to an 8- to 16-fold decrease in daptomycin MIC. The Δ mutant is also 4-fold less resistant to bacitracin but no other cell wall-active antibiotics. Our data indicate that in the absence of HexSDF, the phospholipid membrane composition is altered. In wild-type (WT) C. difficile, the unique glycolipid HNHDRG makes up ~17% of the lipids in the membrane. However, in a Δ mutant, HNHDRG is completely absent. While it is unclear how HNHDRG contributes to daptomycin resistance, the requirement for bacitracin resistance suggests it has a general role in cell membrane biogenesis. Clostridioides difficile is a major cause of hospital-acquired diarrhea and represents an urgent concern due to the prevalence of antibiotic resistance and the rate of recurrent infections. Little is understood about C. difficile membrane lipids, but a unique glycolipid, HNHDRG, has been previously identified in C. difficile and, currently, has not been identified in other organisms. Here, we show that HexSDF and HexRK are required for synthesis of HNHDRG and that production of HNHDRG impacts resistance to daptomycin and bacitracin.

摘要

艰难梭菌是一种革兰氏阳性机会性病原体,每年在美国导致 25 万例医院相关感染、1.2 万例医院相关死亡和 10 亿美元的医疗费用。最近人们对使用达托霉素类似物苏罗替莫(surotomycin)治疗艰难梭菌感染产生了兴趣。达托霉素与磷脂酰甘油和脂质 II 相互作用,破坏膜并阻止肽聚糖合成。艰难梭菌具有异常的脂质膜组成,因为它没有磷脂酰丝氨酸或磷脂酰乙醇胺,并且其膜的约 50%由糖脂组成,包括独特的艰难梭菌脂质氨基己基-己糖基二酰基甘油(HNHDRG)。我们鉴定出一种二组分系统(TCS)HexRK,它是艰难梭菌对达托霉素耐药所必需的。通过转录组测序(RNA-seq),我们发现 HexRK 调节未知功能的三基因操纵子 的表达。基于生物信息学预测, 编码单半乳糖二酰基甘油合酶, 编码多糖脱乙酰酶, 编码 MprF 样翻转酶。 缺失导致达托霉素 MIC 降低 4 倍,而 缺失导致达托霉素 MIC 降低 8-16 倍。Δ突变体对杆菌肽的耐药性也降低了 4 倍,但对其他细胞壁活性抗生素没有耐药性。我们的数据表明,在没有 HexSDF 的情况下,磷脂膜组成发生改变。在野生型(WT)艰难梭菌中,独特的糖脂 HNHDRG 约占膜中脂质的 17%。然而,在 Δ 突变体中,HNHDRG 完全不存在。虽然尚不清楚 HNHDRG 如何有助于达托霉素耐药,但对杆菌肽耐药的要求表明它在细胞膜生物发生中具有普遍作用。艰难梭菌是医院获得性腹泻的主要原因,由于抗生素耐药性的流行和复发性感染的发生率,它代表了一个紧迫的问题。人们对艰难梭菌的膜脂质知之甚少,但以前在艰难梭菌中鉴定出一种独特的糖脂 HNHDRG,目前尚未在其他生物体中鉴定出。在这里,我们表明 HexSDF 和 HexRK 是合成 HNHDRG 所必需的,并且 HNHDRG 的产生影响对达托霉素和杆菌肽的耐药性。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/77de/10128005/a542c97bb7d3/mbio.03397-22-f001.jpg

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