Department of Biological Sciences, Binghamton University, Binghamton, New York, USA.
J Bacteriol. 2012 Sep;194(18):4823-36. doi: 10.1128/JB.00765-12. Epub 2012 Jun 22.
Biofilms are composed of surface-attached microbial communities. A hallmark of biofilms is their profound tolerance of antimicrobial agents. While biofilm drug tolerance has been considered to be multifactorial, our findings indicate, instead, that bacteria within biofilms employ a classical regulatory mechanism to resist the action of antimicrobial agents. Here we report that the transcriptional regulator BrlR, a member of the MerR family of multidrug transport activators, plays a role in the high-level drug tolerance of biofilms formed by Pseudomonas aeruginosa. Expression of brlR was found to be biofilm specific, with brlR inactivation not affecting biofilm formation, motility, or pslA expression but increasing ndvB expression. Inactivation of brlR rendered biofilms but not planktonic cells grown to exponential or stationary phase significantly more susceptible to hydrogen peroxide and five different classes of antibiotics by affecting the MICs and the recalcitrance of biofilms to killing by microbicidal antimicrobial agents. In contrast, overexpression of brlR rendered both biofilms and planktonic cells more tolerant to the same compounds. brlR expression in three cystic fibrosis (CF) isolates was elevated regardless of the mode of growth, suggesting a selection for constitutive brlR expression upon in vivo biofilm formation associated with chronic infections. Despite increased brlR expression, however, isolate CF1-8 was as susceptible to tobramycin as was a ΔbrlR mutant because of a nonsense mutation in brlR. Our results indicate for the first time that biofilms employ a specific regulatory mechanism to resist the action of antimicrobial agents in a BrlR-dependent manner which affects MIC and recalcitrance to killing by microbicidal antimicrobial agents.
生物膜由附着在表面的微生物群落组成。生物膜的一个特点是对抗菌剂有很强的耐受性。虽然生物膜的药物耐受性被认为是多因素的，但我们的研究结果表明，生物膜内的细菌实际上采用了一种经典的调节机制来抵抗抗菌剂的作用。在这里，我们报告转录调节因子 BrlR，一种多药运输激活剂 MerR 家族的成员，在铜绿假单胞菌形成的生物膜的高水平药物耐受性中发挥作用。发现 brlR 的表达是生物膜特异性的，brlR 失活不会影响生物膜的形成、运动或 pslA 的表达，但会增加 ndvB 的表达。brlR 的失活使生物膜而不是处于指数或静止期生长的浮游细胞对过氧化氢和五类不同的抗生素更加敏感，这影响了 MIC 和生物膜对杀菌性抗菌剂杀伤的抵抗力。相比之下，brlR 的过表达使生物膜和浮游细胞对相同的化合物更耐受。在三个囊性纤维化 (CF) 分离株中，brlR 的表达升高，无论生长方式如何，这表明在与慢性感染相关的体内生物膜形成过程中，brlR 的组成型表达是一种选择。然而，尽管 brlR 的表达增加，CF1-8 分离株对妥布霉素的敏感性与 ΔbrlR 突变体一样，因为 brlR 中有一个无意义突变。我们的研究结果首次表明，生物膜采用特定的调节机制以 BrlR 依赖的方式抵抗抗菌剂的作用，这影响 MIC 和杀菌性抗菌剂杀伤的抵抗力。
