在细菌内生孢子形成过程中,发育中的孢子通过吞噬样过程内化到母细胞中,称为吞噬,涉及肽聚糖的合成和水解。吞噬肽聚糖水解需要广泛保守和充分表征的DMP复合物,由Spotify组成,Spotify,和Spotify。相比之下,虽然肽聚糖的合成与吞噬有关,所涉及的蛋白质参与者不太明确。吞噬效率也需要广泛保守的SpoIIIAH-SpoIIQ相互作用,像棘轮一样促进膜在前孔周围迁移。这里,我们使用转座子测序在具有轻度吞噬缺陷的枯草芽孢杆菌突变体中筛选了吞噬所需的其他因子。我们发现YrvJ,肽聚糖水解酶,和MurA仿生MurAB,参与肽聚糖前体合成,是有效吞噬所必需的。细胞学分析表明,当DMP复合物受损时,这两个因素对吞没都很重要,而当取消SpoIIIAH-SpoIIQ棘轮时,还需要MurAB。有趣的是,尽管MurAB对枯草芽孢杆菌孢子形成的重要性,MurA旁系同源物的系统发育分析表明,孢子形成与MurA旁系同源物的数量之间没有相关性,并进一步揭示了第三个MurA旁系同源物的存在,MurAC,在Firmicutes内。总的来说,我们的研究确定了孢子形成过程中有效包膜重塑所需的两个新因素,并强调了肽聚糖前体合成对枯草芽孢杆菌和其他可能的内生孢子形成细菌有效吞噬的重要性。在细菌中的重要性,细胞包膜重塑对细胞生长和分裂至关重要。在细菌发育成高抗性内生孢子(孢子)的过程中也是如此,称为孢子形成。在孢子形成期间,发育中的孢子通过吞噬样过程内化在母细胞内,这对形成孢子的细胞包膜至关重要。吞噬涉及肽聚糖的合成和水解以及在发育中的孢子周围的迁移膜的稳定。重要的是,尽管在吞食过程中涉及肽聚糖的合成,导致这种吞噬分子元件的具体基因仍不清楚。我们的研究确定了吞噬过程中有效包膜重塑所需的两个新因素,并强调了肽聚糖前体合成对于有效吞噬模型生物枯草芽孢杆菌和其他可能的内生孢子形成细菌的重要性。最后,我们的工作强调了合成筛选的力量,以揭示有助于孢子形成过程中重要过程的其他基因。
During bacterial endospore formation, the developing spore is internalized into the mother cell through a phagocytic-like process called engulfment, which involves synthesis and hydrolysis of peptidoglycan. Engulfment peptidoglycan hydrolysis requires the widely conserved and well-characterized DMP complex, composed of SpoIID, SpoIIM, and SpoIIP. In contrast, although peptidoglycan synthesis has been implicated in engulfment, the protein players involved are less well defined. The widely conserved SpoIIIAH-SpoIIQ interaction is also required for engulfment efficiency, functioning like a ratchet to promote membrane migration around the forespore. Here, we screened for additional factors required for engulfment using transposon sequencing in Bacillus subtilis mutants with mild engulfment defects. We discovered that YrvJ, a peptidoglycan hydrolase, and the MurA paralog MurAB, involved in peptidoglycan precursor synthesis, are required for efficient engulfment. Cytological analyses suggest that both factors are important for engulfment when the DMP complex is compromised and that MurAB is additionally required when the SpoIIIAH-SpoIIQ ratchet is abolished. Interestingly, despite the importance of MurAB for sporulation in B. subtilis, phylogenetic analyses of MurA paralogs indicate that there is no correlation between sporulation and the number of MurA paralogs and further reveal the existence of a third MurA paralog, MurAC, within the Firmicutes. Collectively, our studies identify two new factors that are required for efficient envelop remodeling during sporulation and highlight the importance of peptidoglycan precursor synthesis for efficient engulfment in B. subtilis and likely other endospore-forming bacteria. IMPORTANCE In bacteria, cell envelope remodeling is critical for cell growth and division. This is also the case during the development of bacteria into highly resistant endospores (spores), known as sporulation. During sporulation, the developing spore becomes internalized inside the mother cell through a phagocytic-like process called engulfment, which is essential to form the cell envelope of the spore. Engulfment involves both the synthesis and hydrolysis of peptidoglycan and the stabilization of migrating membranes around the developing spore. Importantly, although peptidoglycan synthesis has been implicated during engulfment, the specific genes that contribute to this molecular element of engulfment have remained unclear. Our study identifies two new factors that are required for efficient envelope remodeling during engulfment and emphasizes the importance of peptidoglycan precursor synthesis for efficient engulfment in the model organism Bacillus subtilis and likely other endospore-forming bacteria. Finally, our work highlights the power of synthetic screens to reveal additional genes that contribute to essential processes during sporulation.