摘要
生物膜是细菌细胞的共同体，用于保护它们免受外部不利影响并增强细菌对抗生素和消毒剂的抗性。在这里，我们研究了葡萄糖和氯化钠对沙门氏菌血清型都柏林（S. Dublin）中生物膜形成的调节作用。为了分析群体感应基因luxS的表达水平，我们创建了luxS敲除突变体。此外，研究野生型（WT）和突变株的抗微生物耐药性，疏水性和自诱导剂-2（AI-2）活性。我们的结果显示葡萄糖对S.都柏林生物膜形成不是必需的，但当浓度超过0.1％时对生物膜形成具有抑制作用。发现NaCl在形成生物膜中是不可或缺的，并且在高浓度（> 1.0％）下也发挥抑制作用。生物膜形成后，WT和突变株都显示出显着的MIC增长。观察到S. Dublin的抗生素（氨苄青霉素）生物膜形态的抗性与其浮游生物型相比增加高达32,768倍。然而，与抗生素测试中的WT菌株相比，S. Dublin luxS敲除突变体仅在WT菌株中表现出轻微的差异，尽管它显示出比WT菌株更好的生物膜形成能力。突变菌株也表现出比WT菌株更高的疏水性，这是与生物膜形成有关的特征。由于luxS基因编码的LuxS酶在AI-2合成中发挥重要作用，所以突变株中的群体感应自身诱导物-2（AI-2）的产量显着低于WT株。然而，WT菌株中有限的生物膜形成能力表明AI-2与S. Dublin生物膜形成不直接相关。此外，WT和突变株的基因表达分析揭示了与生物膜应激反应相关的基因的上调和luxS突变株中增强的抗性，这可以提供luxS基因在生物膜形成中的调节作用的证据。

Biofilms are communities of bacterial cells that serve to protect them from external adverse influences and enhance bacterialresistance to antibiotics and sanitizers. Here, we studied the regulatory effects of glucose and sodium chloride on biofilm formation in Salmonella serovar Dublin (S. Dublin). To analyze expression levels of the quorum sensing gene luxS, we created a luxS knockout mutant. Also, antimicrobial resistance, hydrophobicity and autoinducer-2 (AI-2) activity of both the wild-type (WT) and the mutant strain were investigated. Our results revealed that glucose was not essential for S. Dublin biofilm formation but had an inhibitory effect on biofilm formation when the concentration was over 0.1%. NaCl was found to be indispensable in forming biofilm, and it also exerted an inhibitory effect at high concentrations (>1.0%). Both the WT and the mutant strains displayed significant MIC growth after biofilm formation. An increase of up to 32,768 times in the resistance of S. Dublin in biofilm phonotype against antibiotic (ampicillin) compared to its planktonic phonotype was observed. However, S. Dublin luxS knockout mutant only showed slight differences compared to the WT strain in the antimicrobial tests although it displayed better biofilm-forming capacity than the WT strain. The mutant strain also exhibited higher hydrophobicity than the WT strain, which was a feature related to biofilm formation. The production of the quorum sensing autoinducer-2 (AI-2) was significantly lower in the mutant strain than in the WT strain since the LuxS enzyme, encoded by the luxS gene, plays an essential role in AI-2 synthesis. However, the limited biofilm-forming ability in the WT strain indicated AI-2 was not directly related to S. Dublin biofilm formation. Furthermore, gene expression analysis of the WT and mutant strains revealed upregulation of genes related to biofilm stress response and enhanced resistance in the luxS mutant strain, which may provide evidence for the regulatory role of the luxS gene in biofilm formation.

https://www.ncbi.nlm.nih.gov/pubmed/29580499