From the EA4043 Unité Bactéries Pathogènes et Santé (UBaPS), Université Paris-Sud, Université Paris-Saclay, 92290 Châtenay-Malabry.
the Institut Pasteur, Unité Biologie et Génétique de la Paroi Bactérienne, 75724 Paris, and; INSERM, Équipe Avenir, 75015 Paris, France.
J Biol Chem. 2018 Nov 23;293(47):18040-18054. doi: 10.1074/jbc.RA118.004273. Epub 2018 Sep 28.
Spores are produced by many organisms as a survival mechanism activated in response to several environmental stresses. Bacterial spores are multilayered structures, one of which is a peptidoglycan layer called the cortex, containing muramic-δ-lactams that are synthesized by at least two bacterial enzymes, the muramoyl-l-alanine amidase CwlD and the -deacetylase PdaA. This study focused on the spore cortex of , a Gram-positive, toxin-producing anaerobic bacterial pathogen that can colonize the human intestinal tract and is a leading cause of antibiotic-associated diarrhea. Using ultra-HPLC coupled with high-resolution MS, here we found that the spore cortex of the 630Δ strain differs from that of Among these differences, the muramic-δ-lactams represented only 24% in , compared with 50% in CD630_14300 and CD630_27190 were identified as genes encoding the -deacetylases PdaA1 and PdaA2, required for muramic-δ-lactam synthesis. In a mutant, only 0.4% of all muropeptides carried a muramic-δ-lactam modification, and muramic-δ-lactams were absent in the cortex of a double mutant. Of note, the mutant exhibited decreased sporulation, altered germination, decreased heat resistance, and delayed virulence in a hamster infection model. These results suggest a much greater role for muramic-δ-lactams in than in other bacteria, including In summary, the spore cortex of contains lower levels of muramic-δ-lactams than that of , and PdaA1 is the major -deacetylase for muramic-δ-lactam biosynthesis in , contributing to sporulation, heat resistance, and virulence.
芽孢是许多生物为了应对多种环境压力而产生的一种生存机制。细菌芽孢是多层结构，其中一层是称为皮层的肽聚糖层，含有至少两种细菌酶合成的 muramic-δ-内酰胺，即 muramoyl-l-alanine amidase CwlD 和 -deacetylase PdaA。本研究集中于革兰氏阳性、产毒素厌氧细菌病原体 630Δ 菌株的芽孢皮层，该病原体能够定植人类肠道，是抗生素相关性腹泻的主要原因。使用超高效液相色谱法结合高分辨率 MS，我们发现 630Δ 菌株的芽孢皮层与 630_14300 和 CD630_27190 的不同，其中 muramic-δ-内酰胺仅占 630Δ 菌株的 24%，而在 630 中的占比为 50%。CD630_14300 和 CD630_27190 被鉴定为编码 -deacetylases PdaA1 和 PdaA2 的基因，这些基因对于 muramic-δ-内酰胺的合成是必需的。在 pdaA1 突变体中，只有 0.4%的所有肽聚糖携带 muramic-δ-内酰胺修饰，而 pdaA1 和 pdaA2 双突变体的皮层中则没有 muramic-δ-内酰胺。值得注意的是，pdaA1 突变体的芽孢形成减少、发芽改变、耐热性降低，在仓鼠感染模型中的毒力延迟。这些结果表明，muramic-δ-内酰胺在 630Δ 中的作用比在其他细菌中，包括 630 中的作用更大。总之，630Δ 芽孢皮层中的 muramic-δ-内酰胺水平低于 630，PdaA1 是 630 中 muramic-δ-内酰胺生物合成的主要 -deacetylase，有助于芽孢形成、耐热性和毒力。
