D-alanine synthesis and exogenous alanine affect the antimicrobial susceptibility of Staphylococcus aureus.

IF 4.1 2区 医学 Q2 MICROBIOLOGY
Antimicrobial Agents and Chemotherapy Pub Date : 2025-07-02 Epub Date: 2025-06-12 DOI:10.1128/aac.01936-24
Yujin Suzuki, Miki Kawada-Matsuo, Vy Ton That Thuan, Mi Nguyen-Tra Le, Takemasa Sakaguchi, Hitoshi Komatsuzawa
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引用次数: 0

Abstract

D-alanine is an important amino acid for peptidoglycan biosynthesis in Staphylococcus aureus. In addition, D-alanine is used for the modification of teichoic acids to weaken the net surface negative charge, leading to decreased susceptibility to cationic antimicrobial agents. D-alanine synthesis is dependent on only two enzymes. One is alanine racemase, encoded by the alr1 gene, which reversibly converts L-alanine and D-alanine. The other is D-amino acid transaminase, encoded by the dat gene, which synthesizes D-amino acids from α-keto acids and other D-amino acids. In addition, the uptake of L- and D-alanine is dependent on the alanine transporter CycA. To reveal the relationship between D-alanine supply and antimicrobial susceptibility, we evaluated antimicrobial susceptibility in alr1, dat, and cycA inactivation mutants. These mutants, especially the Δalr1 and ΔcycA mutants, presented increased susceptibility to β-lactams, D-cycloserine, bacitracin, lysostaphin, and cationic antimicrobial agents such as aminoglycosides, nisin A, and daptomycin. The net negative charge of the cell surface increased in the Δalr1 and ΔcycA mutants. The changes in susceptibility to antimicrobial agents and cell surface charge were restored in their gene-complemented mutants. Furthermore, in an alanine-depleted medium, the MIC for oxacillin decreased significantly, and the MIC for gentamicin also decreased slightly. Clinical MRSA strains also showed significantly increased susceptibility to oxacillin in the alanine-depleted medium. These results indicate that D-alanine deficiency leads to impaired peptidoglycan and increased net surface negative charge, resulting in increased antimicrobial susceptibility.

d -丙氨酸合成和外源丙氨酸影响金黄色葡萄球菌的抗菌敏感性。
d -丙氨酸是金黄色葡萄球菌肽聚糖生物合成的重要氨基酸。此外,d -丙氨酸被用于修饰天冬酸,以削弱净表面负电荷,从而降低对阳离子抗菌剂的敏感性。d -丙氨酸的合成只依赖于两种酶。一种是丙氨酸外消旋酶,由alr1基因编码,可可逆地转化l -丙氨酸和d -丙氨酸。另一种是d -氨基酸转氨酶,由dat基因编码,由α-酮酸和其他d -氨基酸合成d -氨基酸。此外,L-和d -丙氨酸的摄取依赖于丙氨酸转运体CycA。为了揭示d -丙氨酸供应与抗菌药物敏感性之间的关系,我们评估了alr1、dat和cycA失活突变体的抗菌药物敏感性。这些突变体,尤其是Δalr1和ΔcycA突变体,对β-内酰胺、d -环丝氨酸、杆菌肽、溶葡萄球菌蛋白和阳离子抗菌药物如氨基糖苷类、nisin A和达托霉素的敏感性增加。在Δalr1和ΔcycA突变体中,细胞表面的净负电荷增加。基因补充突变体对抗菌药物的敏感性和细胞表面电荷的变化得以恢复。此外,在缺乏丙氨酸的培养基中,莫西林的MIC显著下降,庆大霉素的MIC也略有下降。临床MRSA菌株在丙氨酸缺失的培养基中也表现出对oxacillin的敏感性显著增加。这些结果表明,d -丙氨酸缺乏导致肽聚糖受损和净表面负电荷增加,从而导致抗菌药物敏感性增加。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
10.00
自引率
8.20%
发文量
762
审稿时长
3 months
期刊介绍: Antimicrobial Agents and Chemotherapy (AAC) features interdisciplinary studies that build our understanding of the underlying mechanisms and therapeutic applications of antimicrobial and antiparasitic agents and chemotherapy.
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