Carvalho Sandra M, Freitas Cláudia S, Oliveira Ana S, Saraiva Lígia M
Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal.
FEMS Microbiol Lett. 2021 Oct 22;368(18). doi: 10.1093/femsle/fnab131.
Staphylococcus aureus is a Gram-positive bacterium with capacity to form biofilms, which constitute an important resistance mechanism and virulence factor. Flavohaemoglobin (Hmp) is a major nitric oxide (NO) detoxifier of several bacteria, including S. aureus. Although Hmp has a well-known physiological role linked to response of planktonic cells to nitrosative stress, its contribution to biofilm formation remains unaddressed. Hence, in this work, we investigated the role of Hmp in biofilm development of a methicillin-resistant S. aureus strain. For this purpose, we exposed the hmp mutant to nitrosative stress and examined its behaviour along biofilm development. We observed that cells inactivated in hmp and grown under nitrosative stress conditions have significantly impaired capacity to develop early stage biofilms. Furthermore, the wild-type biofilm phenotype was fully restored by trans-complementation of hmp in the hmp mutant. Coculture studies of NO-producing macrophages with S. aureus revealed that the hmp mutant has significantly lower capacity to develop biofilm biomass when compared with the wild type. Thus, we concluded that the pathogen S. aureus relies on Hmp to establish viable biofilms in the presence of cells of the host innate immune system.
金黄色葡萄球菌是一种革兰氏阳性细菌，具有形成生物膜的能力，生物膜构成了一种重要的抗性机制和毒力因子。黄素血红蛋白（Hmp）是包括金黄色葡萄球菌在内的多种细菌的主要一氧化氮（NO）解毒剂。尽管Hmp具有与浮游细胞对亚硝化应激反应相关的众所周知的生理作用，但其对生物膜形成的贡献仍未得到解决。因此，在这项工作中，我们研究了Hmp在耐甲氧西林金黄色葡萄球菌菌株生物膜形成中的作用。为此，我们将hmp突变体暴露于亚硝化应激下，并检查其在生物膜形成过程中的行为。我们观察到，在亚硝化应激条件下生长的hmp失活细胞形成早期生物膜的能力显著受损。此外，通过在hmp突变体中对hmp进行反式互补，野生型生物膜表型得以完全恢复。将产生NO的巨噬细胞与金黄色葡萄球菌进行共培养研究发现，与野生型相比，hmp突变体形成生物膜生物量的能力显著降低。因此，我们得出结论，病原体金黄色葡萄球菌在宿主固有免疫系统细胞存在的情况下依赖Hmp来建立有活力的生物膜。
