Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
Res Microbiol. 2022 May-Jun;173(4-5):103922. doi: 10.1016/j.resmic.2022.103922. Epub 2022 Jan 31.
Cadmium (Cd) is a heavy metal used as raw material for several fertilizers and pesticides. The increase of Cd concentration in soils has been observed in cultivated areas, affecting animals, plants, and microorganisms. Gluconacetobacter diazotrophicus is a plant growth-promoting bacterium able to survive under adverse environmental conditions. Here, we investigated key mechanisms involved with the resistance of G. diazotrophicus to Cd. Proteomic analyses revealed that the main pathways regulated in response to Cd are nutrient uptake, multidrug efflux pumps, response to oxidative stress, and protein quality control system. Extracytoplasmic proteins related to multidrug efflux pumps were up-accumulated, while several proteins related to nutrients uptake were down-accumulated. The relevance of these pathways for bacterial resistance to Cd was investigated by reverse genetic analysis using mutants defective for nutrient uptake (tdbr, ompW, and oprB), multidrug efflux (czcC), response to oxidative stress (ggt), and protein quality control system (clpX). Our data demonstrated the essential role of the tdbr and czcC genes for resistance to Cd in G. diazotrophicus. These results contribute to a better understanding of the resistance mechanisms to Cd in G. diazotrophicus, shedding light on responses associated with extracytoplasmic compartments.
镉（Cd）是一种重金属，被用作几种肥料和农药的原料。在耕种地区，土壤中镉浓度的增加已经被观察到，这影响了动物、植物和微生物。土壤杆菌（Gluconacetobacter diazotrophicus）是一种能够在不利环境条件下生存的植物促生细菌。在这里，我们研究了与 G. diazotrophicus 对 Cd 抗性相关的关键机制。蛋白质组学分析表明，受 Cd 调控的主要途径是营养物质摄取、多药外排泵、应对氧化应激和蛋白质质量控制系统。与多药外排泵相关的细胞外蛋白被大量积累，而与营养物质摄取相关的几种蛋白则被大量减少。通过对营养物质摄取（tdbr、ompW 和 oprB）、多药外排（czcC）、应对氧化应激（ggt）和蛋白质质量控制系统（clpX）缺陷的突变体进行反向遗传学分析，研究了这些途径对细菌抗 Cd 的相关性。我们的数据表明，tdbr 和 czcC 基因对 G. diazotrophicus 抵抗 Cd 至关重要。这些结果有助于更好地理解 G. diazotrophicus 对 Cd 的抗性机制，阐明与细胞外隔室相关的反应。
