Division of Experimental Infection Medicine, Department of Translational Medicine, Lund University, Malmö, Sweden.
Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden.
Sci Rep. 2020 Dec 31;10(1):22455. doi: 10.1038/s41598-020-80233-0.
Streptococcus pneumoniae (the pneumococcus) colonizes the human nasopharynx by forming multicellular biofilms. Due to the high level of asymptomatic carriage, transition to infections, such as otitis media, pneumonia, sepsis, and meningitis, occurs often enough that the pneumococcus remains a major cause of disease and death globally. Virus infection and virus-induced responses, such as increased temperature (fever), trigger release of virulent bacteria from colonizing biofilms. The exact mechanisms involved in pneumococcal egress during biofilm dispersal remain unknown, although we hypothesize that disruption of the biofilm matrix encasing the bacteria is necessary. Here, we utilized established in vitro biofilm dispersal models to investigate the involvement of proteases in bacterial egress from pneumococcal biofilms. We demonstrate the importance of protease activity, both through increased bacterial release following addition of proteases and reduced heat-induced biofilm dispersal in the presence of protease inhibitors. We identify a key role for the surface-exposed serine protease HtrA, but not PrtA, in heat-induced biofilm dispersal. Bacterial release from htrA-negative biofilms was significantly reduced compared to wild-type isogenic strains but was restored and increased above wild-type levels following addition of recombinant HtrA. Understanding the specific mechanisms involved in bacterial egress may provide novel targets for future strategies aimed to specifically interfere with disease progression without disturbing nasopharyngeal biofilm colonization.
肺炎链球菌（肺炎球菌）通过形成多细胞生物膜在人类鼻咽部定植。由于无症状携带的水平很高，向中耳炎、肺炎、败血症和脑膜炎等感染的转变经常发生，因此肺炎球菌仍然是全球主要的疾病和死亡原因。病毒感染和病毒引起的反应，如体温升高（发热），会触发定植生物膜中有毒细菌的释放。尽管我们假设破坏包裹细菌的生物膜基质是必要的，但在生物膜分散过程中肺炎球菌逸出的确切机制仍不清楚。在这里，我们利用已建立的体外生物膜分散模型来研究蛋白酶在肺炎球菌生物膜中细菌逸出的作用。我们通过添加蛋白酶后增加细菌释放以及在存在蛋白酶抑制剂时减少热诱导的生物膜分散来证明蛋白酶活性的重要性。我们确定了表面暴露的丝氨酸蛋白酶 HtrA 在热诱导的生物膜分散中的关键作用，但 PrtA 没有作用。与野生型同基因株相比，htra 阴性生物膜的细菌释放明显减少，但在添加重组 HtrA 后，细菌释放恢复并高于野生型水平。了解细菌逸出所涉及的特定机制可能为未来的策略提供新的靶点，这些策略旨在在不干扰鼻咽部生物膜定植的情况下特异性干扰疾病进展。
