Present address: National Institute of Animal Biotechnology, Hyderabad, Telangana, PIN-500032, India.
Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal, PIN-721302, India.
Microbiology (Reading). 2021 Mar;167(3). doi: 10.1099/mic.0.001031. Epub 2021 Feb 4.
low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.
低分子量（LMM）青霉素结合蛋白（PBPs）有助于水解细胞壁中的肽聚糖片段，并将其回收回正在生长的肽聚糖基质中，除了它们在生物膜形成中的报道外。生物膜是粘性细菌细胞分泌的额外聚合物物质的外部粘液层，为自己形成可居住的小生境。在这里，我们假设 LMM PBPs 参与调节生物膜形成过程中其额外聚合物物质中普遍存在的胞外多糖（EPS）的性质。因此，本研究包括评估 CS109 LMM PBP 缺失突变体的生理特性，以解决生物膜形成能力、生存能力和表面粘附问题。最后，从亲本 CS109 及其 ΔPBP4 和 ΔPBP5 突变体中纯化和分析了存在的糖。LMM PBP 的缺失减少了生物膜形成、细菌粘附及其在生物膜中的生存能力。缺失还减少了 ΔPBP4 和 ΔPBP5 突变体的 EPS 产生，其纯化表明与亲本相比整体负电荷增加。此外，来自两种突变体的 EPS 分析表明出现了一种异常的糖，木糖，在 CS109 中不存在。因此，可以推测 LMM PBP 突变体中生物膜形成减少的原因可能是随后产生木糖醇和戊糖磷酸途径的标准流动受阻。
