Mathlouthi A, Pennacchietti E, De Biase D
Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Laboratory affiliated to the Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Corso della Repubblica 79, 04100 Latina, Italy.
Université de Carthage, Faculté des Sciences de Bizerte, Département des Sciences de la Vie, Laboratoire de Biosurveillance de l'Environnement (LR01/ES14), Unité d'Ecotoxicologie, Route de Tunis, 7021 Zarzouna, Tunisie.
Acta Naturae. 2018 Oct-Dec;10(4):129-132.
Acid resistance (AR) in is an important trait that protects this microorganism from the deleterious effect of low-pH environments. Reports on biofilm formation in K12 showed that the genes participating in AR were differentially expressed. Herein, we investigated the relationship between AR genes, in particular those coding for specific transcriptional regulators, and their biofilm-forming ability at the phenotypic level. The latter was measured in 96-well plates by staining the bacteria attached to the well, following 24-hour growth under static conditions, with crystal violet. The growth conditions were as follows: Luria Bertani (LB) medium at neutral and acidic pH, at 37°C or 25°C. We observed that the three major transcriptional regulators of the AR genes (, , ) only marginally affected biofilm formation in . However, a striking and novel finding was the different abilities of all the tested strains to form a biofilm depending on the temperature and pH of the medium: LB, pH 7.4, strongly supported biofilm formation at 25°C, with biofilm being hardly detectable at 37°C. On the contrary, LB, pH 5.5, best supported biofilm formation at 37°C. Moreover, we observed that when carried a plasmid, the presence of the plasmid itself affected the ability to develop a biofilm, typically by increasing its formation. This phenomenon varies from plasmid to plasmid, depends on growth conditions, and, to the best of our knowledge, remains largely uninvestigated.
的耐酸性（AR）是一种重要特性，可保护这种微生物免受低pH环境的有害影响。关于K12中生物膜形成的报告表明，参与AR的基因存在差异表达。在此，我们在表型水平上研究了AR基因，特别是那些编码特定转录调节因子的基因与其生物膜形成能力之间的关系。后者通过在静态条件下培养24小时后，用结晶紫对附着在96孔板孔上的细菌进行染色来测定。生长条件如下：在中性和酸性pH值的Luria Bertani（LB）培养基中，温度为37°C或25°C。我们观察到，AR基因的三个主要转录调节因子（、、）对中生物膜形成的影响微乎其微。然而，一个显著且新颖的发现是，所有测试菌株形成生物膜的能力因培养基的温度和pH值而异：LB，pH 7.4，在25°C时强烈支持生物膜形成，在37°C时几乎检测不到生物膜。相反，LB，pH 5.5，在37°C时最有利于生物膜形成。此外，我们观察到，当携带质粒时，质粒本身的存在会影响生物膜形成能力，通常会增加其形成。这种现象因质粒而异，取决于生长条件，据我们所知，在很大程度上仍未得到充分研究。
