Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater, Oklahoma, USA.
mSphere. 2023 Oct 24;8(5):e0037423. doi: 10.1128/msphere.00374-23. Epub 2023 Sep 27.
is an opportunistic pathogen that is widely known for infecting patients with underlying conditions. This species often survives antibiotic therapy by forming biofilms, in which the cells produce a protective extracellular matrix. also produces virulence factors that enhance its ability to cause disease. One signaling pathway that influences virulence is the nitrogen-related phosphotransferase system (Nitro-PTS), which consists of an initial phosphotransferase, , a phosphocarrier, PtsO, and a terminal phosphate receptor, PtsN. The physiological role of the Nitro-PTS in is poorly understood. However, PtsN, when deprived of its upstream phosphotransfer proteins, has an antagonistic effect on biofilm formation. We thus conducted a transposon mutagenesis screen in an unphosphorylated-PtsN (i.e., ∆) background to identify downstream proteins with unacknowledged roles in PtsN-mediated biofilm suppression. We found an unstudied gene, , whose disruption restored biofilm production. This gene encodes a predicted phospholipase with signature alpha/beta hydrolase folds and a lipase signature motif with an active-site Ser residue. Hence, we renamed the gene , for iofilm-mpacting hosphoipase. Deletion of in a ∆ background increased biofilm formation, supporting the idea that BipL is responsible for reducing biofilm formation in strains with unphosphorylated PtsN. Moreover, substituting the putative catalytic Ser for Ala phenocopied deletion, indicating that this residue is important for the biofilm-suppressive activity of BipL . As our preliminary data suggest that BipL is a lipase, we performed lipidomics to detect changes in the lipid profile due to deletion and found changes in some lipid species. IMPORTANCE Biofilm formation by bacteria occurs when cells secrete an extracellular matrix that holds them together and shields them from environmental insults. Biofilms of bacterial opportunistic human pathogens such as pose a substantial challenge to clinical antimicrobial therapy. Hence, a more complete knowledge about the bacterial factors that influence and regulate production of the biofilm matrix is one key to formulate more effective therapeutic strategies. In this study, we screen for factors that are important for reducing biofilm matrix production in certain genetic backgrounds. We unexpectedly found a gene encoding a putative lipase enzyme and showed that its predicted catalytic site is important for its ability to reduce biofilm formation. Our findings suggest that lipase enzymes have previously uncharacterized functions in biofilm matrix regulation.
是一种机会性病原体，广泛存在于感染有潜在疾病的患者中。该物种常通过形成生物膜来存活于抗生素治疗中，在生物膜中，细胞会产生一种保护性的细胞外基质。还会产生增强其致病能力的毒力因子。影响毒力的信号通路之一是氮相关磷酸转移酶系统（Nitro-PTS），它由初始磷酸转移酶、磷酸载体 PtsO 和末端磷酸受体 PtsN 组成。氮相关磷酸转移酶系统在中的生理作用尚未完全了解。然而，当 PtsN 失去其上游磷酸转移蛋白时，会对生物膜形成产生拮抗作用。因此，我们在未磷酸化的 PtsN（即 ∆）背景下进行转座子诱变筛选，以鉴定在 PtsN 介导的生物膜抑制中具有未被认可作用的下游蛋白。我们发现了一个未被研究的基因，其失活恢复了生物膜的产生。该基因编码一种预测的磷脂酶，具有特征性的α/β水解酶折叠和具有活性位点 Ser 残基的脂肪酶特征基序。因此，我们将该基因重新命名为，用于生物膜影响的磷酸脂酶。在 ∆ 背景下缺失会增加生物膜的形成，支持 BipL 负责减少未磷酸化 PtsN 菌株生物膜形成的观点。此外，用假定的催化 Ser 取代 Ala 表型类似于缺失，表明该残基对于 BipL 的生物膜抑制活性很重要。由于我们的初步数据表明 BipL 是一种脂肪酶，我们进行了脂质组学检测由于缺失而导致的脂质谱变化，发现了一些脂质种类的变化。重要性 当细胞分泌一种将它们聚集在一起并使其免受环境侵害的细胞外基质时，细菌就会形成生物膜。细菌机会性病原体（如 ）的生物膜形成对临床抗菌治疗构成了重大挑战。因此，更全面地了解影响和调节生物膜基质产生的细菌因素是制定更有效的治疗策略的关键之一。在这项研究中，我们筛选了在某些遗传背景下对减少生物膜基质产生很重要的因素。我们出人意料地发现了一个编码假定脂肪酶的基因，并表明其预测的催化位点对于其降低生物膜形成的能力很重要。我们的发现表明，脂肪酶在生物膜基质调节中具有以前未被描述的功能。
