Department of Biological Sciences, Binghamton University, Binghamton, New York, United States of America.
Binghamton Biofilm Research Center, Binghamton University, Binghamton, New York, United States of America.
PLoS One. 2019 Feb 14;14(2):e0212275. doi: 10.1371/journal.pone.0212275. eCollection 2019.
Outer Membrane Vesicles (OMVs) are ubiquitous in bacterial environments and enable interactions within and between species. OMVs are observed in lab-grown and environmental biofilms, but our understanding of their function comes primarily from planktonic studies. Planktonic OMVs assist in toxin delivery, cell-cell communication, horizontal gene transfer, small RNA trafficking, and immune system evasion. Previous studies reported differences in size and proteomic cargo between planktonic and agar plate biofilm OMVs, suggesting possible differences in function between OMV types. In Pseudomonas aeruginosa interstitial biofilms, extracellular vesicles were reported to arise through cell lysis, in contrast to planktonic OMV biogenesis that involves the Pseudomonas Quinolone Signal (PQS) without appreciable autolysis. Differences in biogenesis mechanism could provide a rationale for observed differences in OMV characteristics between systems. Using nanoparticle tracking, we found that P. aeruginosa PAO1 planktonic and biofilm OMVs had similar characteristics. However, P. aeruginosa PA14 OMVs were smaller, with planktonic OMVs also being smaller than their biofilm counterparts. Large differences in Staphylococcus killing ability were measured between OMVs from different strains, and a smaller within-strain difference was recorded between PA14 planktonic and biofilm OMVs. Across all conditions, the predatory ability of OMVs negatively correlated with their size. To address biogenesis mechanism, we analyzed vesicles from wild type and pqsA mutant biofilms. This showed that PQS is required for physiological-scale production of biofilm OMVs, and time-course analysis confirmed that PQS production precedes OMV production as it does in planktonic cultures. However, a small sub-population of vesicles was detected in pqsA mutant biofilms whose size distribution more resembled sonicated cell debris than wild type OMVs. These results support the idea that, while a small and unique population of vesicles in P. aeruginosa biofilms may result from cell lysis, the PQS-induced mechanism is required to generate the majority of OMVs produced by wild type communities.
外膜囊泡（OMVs）在细菌环境中普遍存在，并促进物种内和物种间的相互作用。OMVs 存在于实验室培养的和环境生物膜中，但我们对其功能的理解主要来自浮游生物研究。浮游生物 OMVs 有助于毒素传递、细胞间通讯、水平基因转移、小 RNA 运输和免疫系统逃避。先前的研究报告称，浮游生物和琼脂平板生物膜 OMVs 之间在大小和蛋白质组货物方面存在差异，这表明 OMV 类型之间可能存在功能差异。在铜绿假单胞菌间质生物膜中，据报道细胞裂解会导致细胞外囊泡的产生，而浮游生物 OMV 的生物发生则涉及假单胞菌喹诺酮信号（PQS），而没有明显的自溶。生物发生机制的差异可能为系统间 OMV 特征观察到的差异提供了一个合理的解释。使用纳米颗粒跟踪技术，我们发现铜绿假单胞菌 PAO1 浮游生物和生物膜 OMVs 具有相似的特征。然而，铜绿假单胞菌 PA14 OMVs 较小，浮游生物 OMVs 也比其生物膜对应物小。不同菌株的 OMVs 在杀伤金黄色葡萄球菌方面存在很大差异，而 PA14 浮游生物和生物膜 OMVs 之间的同一菌株内差异则较小。在所有条件下，OMVs 的捕食能力与它们的大小呈负相关。为了解决生物发生机制问题，我们分析了野生型和 pqsA 突变体生物膜中的囊泡。结果表明，PQS 是生理规模生物膜 OMV 产生所必需的，时程分析证实，PQS 的产生先于浮游生物培养物中的 OMV 产生。然而，在 pqsA 突变体生物膜中检测到一小部分囊泡，其大小分布更类似于超声处理的细胞碎片，而不是野生型 OMVs。这些结果支持这样一种观点，即虽然铜绿假单胞菌生物膜中可能存在一小部分来自细胞裂解的独特囊泡群体，但需要 PQS 诱导的机制来产生野生型群落产生的大多数 OMVs。
