Modi Malvika, Chauhan Deepika, Gilmore Michael C, Cava Felipe, Priyadarshini Richa
Department of Life Sciences, School of Natural Sciences, Shiv Nadar Institution of Eminence, Gautam Buddha Nagar, Uttar Pradesh, India.
Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden.
mBio. 2025 Apr 9;16(4):e0297524. doi: 10.1128/mbio.02975-24. Epub 2025 Mar 11.
Peptidoglycan (PG)-modifying enzymes play a crucial role in cell wall remodeling, essential for growth and division. Cell wall degradation products are transported to the cytoplasm and recycled back in most gram-negative bacteria, and PG recycling is also linked to β-lactam resistance in many bacteria. is intrinsically resistant to β-lactams. Recently, it was shown that a soluble lytic transglycosylase, SdpA, is essential for β-lactam resistance. However, the precise role of SdpA in β-lactam resistance is unknown. This study investigated the PG recycling pathway and its role in antibiotic resistance in . Anhydromuropeptides generated by the action of lytic transglycosylases (LTs) are transported to the cytoplasm by the permease AmpG. encodes an homolog, and deletion mutants of and are sensitive to β-lactams. The deletion mutant displays a significant accumulation of anhydromuropeptides in the periplasm of demonstrating its essential role in PG recycling. While single knockout mutants of and exhibit no growth defects, double-deletion mutants (∆∆) exhibit severe growth and morphological defects. These double mutants also show enhanced sensitivity to β-lactams. Analysis of soluble muropeptides in wild-type (WT), ∆, and ∆ mutants revealed reduced levels of PG precursors (UDP-GlcNAc, UDP-MurNAc, and UDP-MurNAc-P5), suggesting that PG recycling products contribute toward PG biosynthesis. Furthermore, supplementing the growth media with GlcNAc sugar enhanced the fitness of ∆ and ∆ mutants under β-lactam stress. In conclusion, our study indicates that defects in PG recycling compromise cell wall biogenesis, leading to antibiotic sensitivity in .β-lactam antibiotics target the peptidoglycan cell wall biosynthetic pathway in bacteria. In response to antibiotic pressures, bacteria have developed various resistance mechanisms. In many gram-negative species, cell wall degradation products are transported into the cytoplasm and induce the expression of β-lactamase enzymes. In this study, we investigated the cell wall recycling pathway and its role in antibiotic resistance in . Based on our data and prior studies, we propose that cell wall degradation products are utilized for the synthesis of peptidoglycan precursors in the cytoplasm. A deficiency in cell wall recycling leads to cell wall defects and increased antibiotic sensitivity in . These findings are crucial for understanding antibiotic resistance mechanisms in bacteria.
肽聚糖（PG）修饰酶在细胞壁重塑过程中发挥着关键作用，而细胞壁重塑对于细菌的生长和分裂至关重要。在大多数革兰氏阴性菌中，细胞壁降解产物会被转运至细胞质并进行再循环利用，并且PG再循环也与许多细菌对β-内酰胺类抗生素的耐药性相关。[细菌名称]对β-内酰胺类抗生素具有内在抗性。最近的研究表明，一种可溶性溶菌转糖基酶SdpA对于β-内酰胺类抗生素耐药性至关重要。然而，SdpA在β-内酰胺类抗生素耐药性中的确切作用尚不清楚。本研究调查了[细菌名称]中的PG再循环途径及其在抗生素耐药性中的作用。由溶菌转糖基酶（LTs）作用产生的脱无水肽聚糖通过通透酶AmpG转运至细胞质。[细菌名称]编码一种[蛋白名称]的同源物，[基因名称1]和[基因名称2]的缺失突变体对β-内酰胺类抗生素敏感。[基因名称1]缺失突变体在[细菌名称]的周质中显示出脱无水肽聚糖的显著积累，这表明其在PG再循环中起着至关重要的作用。虽然[基因名称1]和[基因名称2]的单敲除突变体没有生长缺陷，但双缺失突变体（∆[基因名称1]∆[基因名称2]）表现出严重的生长和形态缺陷。这些双突变体对β-内酰胺类抗生素也表现出更高的敏感性。对野生型（WT）、∆[基因名称1]和∆[基因名称2]突变体中可溶性肽聚糖的分析表明，PG前体（UDP-GlcNAc、UDP-MurNAc和UDP-MurNAc-P5）水平降低，这表明PG再循环产物有助于[细菌名称]的PG生物合成。此外，在生长培养基中添加GlcNAc糖可增强∆[基因名称1]和∆[基因名称2]突变体在β-内酰胺类抗生素压力下的适应性。总之，我们的研究表明，PG再循环缺陷会损害细胞壁生物合成，导致[细菌名称]对抗生素敏感。β-内酰胺类抗生素靶向细菌中的肽聚糖细胞壁生物合成途径。为应对抗生素压力，细菌已发展出多种耐药机制。在许多革兰氏阴性菌中，细胞壁降解产物被转运至细胞质并诱导β-内酰胺酶的表达。在本研究中，我们调查了[细菌名称]中的细胞壁再循环途径及其在抗生素耐药性中的作用。基于我们的数据和先前的研究，我们提出细胞壁降解产物可用于细胞质中肽聚糖前体的合成。细胞壁再循环缺陷会导致细胞壁缺陷并增加[细菌名称]对抗生素的敏感性。这些发现对于理解细菌的抗生素耐药机制至关重要。
