Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, Iowa, United States of America.
Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa United States of America.
PLoS One. 2022 Oct 13;17(10):e0276046. doi: 10.1371/journal.pone.0276046. eCollection 2022.
Outer membrane protein A (OmpA) is one of the most abundant outer membrane proteins of Gram-negative bacteria and is known to have patterns of sequence variations at certain amino acids-allelic variation-in Escherichia coli. Here we subjected seven exemplar OmpA alleles expressed in a K-12 (MG1655) ΔompA background to further characterization. These alleles were observed to significantly impact cell surface charge (zeta potential), cell surface hydrophobicity, biofilm formation, sensitivity to killing by neutrophil elastase, and specific growth rate at 42°C and in the presence of acetate, demonstrating that OmpA is an attractive target for engineering cell surface properties and industrial phenotypes. It was also observed that cell surface charge and biofilm formation both significantly correlate with cell surface hydrophobicity, a cell property that is increasingly intriguing for bioproduction. While there was poor alignment between the observed experimental values relative to the known sequence variation, differences in hydrophobicity and biofilm formation did correspond to the identity of residue 203 (N vs T), located within the proposed dimerization domain. The relative abundance of the (I, δ) allele was increased in extraintestinal pathogenic E. coli (ExPEC) isolates relative to environmental isolates, with a corresponding decrease in (I, α) alleles in ExPEC relative to environmental isolates. The (I, α) and (I, δ) alleles differ at positions 203 and 251. Variations in distribution were also observed among ExPEC types and phylotypes. Thus, OmpA allelic variation and its influence on OmpA function warrant further investigation.
外膜蛋白 A（OmpA）是革兰氏阴性菌中最丰富的外膜蛋白之一，已知在大肠杆菌中某些氨基酸（等位基因变异）存在序列变异模式。在这里，我们对在 K-12（MG1655）ΔompA 背景下表达的七个外膜蛋白 A 等位基因进行了进一步的特征描述。这些等位基因显著影响细胞表面电荷（Zeta 电位）、细胞表面疏水性、生物膜形成、对中性粒细胞弹性蛋白酶杀伤的敏感性以及在 42°C 和存在醋酸盐的情况下的特定生长速率，这表明 OmpA 是工程细胞表面特性和工业表型的有吸引力的目标。还观察到细胞表面电荷和生物膜形成都与细胞表面疏水性显著相关，这是一个对于生物生产越来越有吸引力的细胞特性。虽然观察到的实验值与已知的序列变异之间的一致性较差，但疏水性和生物膜形成的差异确实与位于二聚化结构域内的残基 203（N 与 T）的身份相对应。位于外膜蛋白 A 二聚化结构域的第 203 位氨基酸（N 或 T）决定了外膜蛋白 A 的 I 型和 δ 型，在肠道外致病性大肠杆菌（ExPEC）分离株中，I 型等位基因（I，δ）的相对丰度高于环境分离株，而 ExPEC 中 I 型等位基因（I，α）的相对丰度则低于环境分离株。I 型和 δ 型等位基因在外膜蛋白 A 第 203 位和 251 位氨基酸的序列存在差异。此外，还观察到 ExPEC 不同类型和进化枝之间的分布也存在差异。因此，外膜蛋白 A 等位基因的变异及其对 OmpA 功能的影响值得进一步研究。
