Wageningen University & Research, Laboratory of Food Microbiology, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
Wageningen University & Research, Laboratory of Food Microbiology, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
Int J Food Microbiol. 2018 May 20;273:20-27. doi: 10.1016/j.ijfoodmicro.2018.03.009. Epub 2018 Mar 15.
Listeria monocytogenes is a food-borne pathogen that can grow as a biofilm on surfaces. Biofilm formation in food-processing environments is a big concern for food safety, as it can cause product contamination through the food-processing line. Although motile aerobic bacteria have been described to form biofilms at the air-liquid interface of cell cultures, to our knowledge, this type of biofilm has not been described in L. monocytogenes before. In this study we report L. monocytogenes biofilm formation at the air-liquid interface of aerobically grown cultures, and that this phenotype is specifically induced when the media is supplemented with glycerol as a carbon and energy source. Planktonic growth, metabolic activity assays and HPLC measurements of glycerol consumption over time showed that glycerol utilization in L. monocytogenes is restricted to growth under aerobic conditions. Gene expression analysis showed that genes encoding the glycerol transporter GlpF, the glycerol kinase GlpK and the glycerol 3-phosphate dehydrogenase GlpD were upregulated in the presence of oxygen, and downregulated in absence of oxygen. Additionally, motility assays revealed the induction of aerotaxis in the presence of glycerol. Our results demonstrate that the formation of biofilms at the air-liquid interface is dependent on glycerol-induced aerotaxis towards the surface of the culture, where L. monocytogenes has access to higher concentrations of oxygen, and is therefore able to utilize this compound as a carbon source.
李斯特菌是一种食源性病原体，能够在表面形成生物膜。食品加工环境中的生物膜形成是食品安全的一个大问题，因为它可以通过食品加工线导致产品污染。尽管已经描述了能动需氧细菌在细胞培养物的气液界面形成生物膜，但据我们所知，以前尚未在李斯特菌中描述过这种类型的生物膜。在这项研究中，我们报告了李斯特菌在有氧培养物的气液界面形成生物膜的现象，并且当培养基中补充甘油作为碳源和能源时，会特异性地诱导这种表型。浮游生长、代谢活性测定和 HPLC 测量甘油随时间的消耗表明，李斯特菌中甘油的利用仅限于有氧条件下的生长。基因表达分析表明，编码甘油转运蛋白 GlpF、甘油激酶 GlpK 和甘油 3-磷酸脱氢酶 GlpD 的基因在有氧存在的情况下上调，在无氧存在的情况下下调。此外，运动性测定显示在存在甘油的情况下诱导了趋氧性。我们的结果表明，气液界面生物膜的形成依赖于甘油诱导的向培养物表面的趋氧性，在那里李斯特菌可以接触到更高浓度的氧气，因此能够将这种化合物用作碳源。
