铜绿假单胞菌是一种抵抗环境胁迫的多功能病原体,例如次优pH。由于暴露于环境压力,铜绿假单胞菌显示改变的毒力相关表型。这项研究调查了与在中性培养基(pH7.2)中生长的细菌相比,铜绿假单胞菌在轻度低pH(pH5.0)下进行的修饰。结果表明,在弱酸性环境中,双组分系统基因(phoP/phoQ和pmrA/pmrB)的表达,脂质A重塑基因,如arnT和pagP和毒力基因,即,pqsE和rhla,是诱导的。此外,通过添加4-氨基阿拉伯糖(1-Ara4N)来修饰在轻度低pH下生长的细菌的脂质A。此外,产生的毒力因子,如鼠李糖脂,海藻酸盐,在温和的低pH环境中,膜囊泡明显高于中性介质。有趣的是,在温和的低pH下,铜绿假单胞菌产生具有较高生物膜生物量的较厚生物膜。此外,关于内膜粘度和渗透性的研究表明,轻度低的pH值会导致内膜渗透性降低并增加其粘度。此外,尽管PhoP很重要,PhoQ,PmrA,革兰氏阴性菌中的PmrB对低pH胁迫的反应,我们观察到,这些两组分系统的缺失对铜绿假单胞菌包膜的重塑没有显著影响.鉴于铜绿假单胞菌在其宿主感染期间可能会遇到弱酸性环境,在设计针对铜绿假单胞菌的抗菌策略时,必须考虑细菌在这种条件下进行的改变。重要性铜绿假单胞菌在宿主中建立感染时遇到酸性pH的环境。细菌产生改变的表型以耐受环境pH的适度降低。在细菌包膜的水平上,修饰的脂质A组成以及细菌内膜渗透性和流动性的降低是铜绿假单胞菌在轻度低pH下经历的变化。此外,细菌在弱酸性环境中更有可能形成生物膜。总的来说,铜绿假单胞菌表型的这些改变阻碍了抗菌活性。因此,考虑细菌在低pH下的生理变化有助于设计和实施针对这种敌对微生物的抗微生物方法。
Pseudomonas aeruginosa is a versatile pathogen that resists environmental stress, such as suboptimal pH. As a result of exposure to environmental stress, P. aeruginosa shows an altered virulence-related phenotype. This study investigated the modifications that P. aeruginosa undertakes at a mildly low pH (pH 5.0) compared with the bacteria grown in a neutral medium (pH 7.2). Results indicated that in a mildly acidic environment, expression of two-component system genes (phoP/phoQ and pmrA/pmrB), lipid A remodeling genes such as arnT and pagP and virulence genes, i.e., pqsE and rhlA, were induced. Moreover, lipid A of the bacteria grown at a mildly low pH is modified by adding 4-amino-arabinose (l-Ara4N). Additionally, the production of virulence factors such as rhamnolipid, alginate, and membrane vesicles is significantly higher in a mildly low-pH environment than in a neutral medium. Interestingly, at a mildly low pH, P. aeruginosa produces a thicker biofilm with higher biofilm biomass. Furthermore, studies on inner membrane viscosity and permeability showed that a mildly low pH causes a decrease in the inner membrane permeability and increases its viscosity. Besides, despite the importance of PhoP, PhoQ, PmrA, and PmrB in Gram-negative bacteria for responding to low pH stress, we observed that the absence of each of these two-component systems does not meaningfully impact the remodeling of the P. aeruginosa envelope. Given that P. aeruginosa is likely to encounter mildly acidic environments during infection in its host, the alterations that the bacterium undertakes under such conditions must be considered in designing antibacterial strategies against P. aeruginosa. IMPORTANCE P. aeruginosa encounters environments with acidic pH when establishing infections in hosts. The bacterium develops an altered phenotype to tolerate a moderate decrease in the environmental pH. At the level of the bacterial envelope, modified lipid A composition and a reduction of the bacterial inner membrane permeability and fluidity are among the changes P. aeruginosa undergoes at a mildly low pH. Also, the bacterium is more likely to form biofilm in a mildly acidic environment. Overall, these alterations in the P. aeruginosa phenotype put obstacles in the way of antibacterial activities. Thus, considering physiological changes in the bacterium at low pH helps design and implement antimicrobial approaches against this hostile microorganism.