Rodrigues Carolina M, Takita Marco A, Coletta-Filho Helvécio D, Olivato Jacqueline C, Caserta Raquel, Machado Marcos A, de Souza Alessandra A
Centro APTA Citros Sylvio Moreira, Instituto Agronômico de Campinas, Cordeirópolis, Brazil.
Appl Microbiol Biotechnol. 2008 Jan;77(5):1145-57. doi: 10.1007/s00253-007-1232-1. Epub 2007 Nov 9.
Xylella fastidiosa is a phytopathogen that causes diseases in different plant species. The development of disease symptoms is associated to the blockage of the xylem vessels caused by biofilm formation. In this study, we evaluated the sensitivity of biofilm and planktonic cells to copper, one of the most important antimicrobial agents used in agriculture. We measured the exopolysaccharides (EPS) content in biofilm and planktonic cells and used real-time reverse transcription polymerase chain reaction to evaluate the expression of the genes encoding proteins involved in cation/multidrug extrusion (acrA/B, mexE/czcA, and metI) and others associated with different copper resistance mechanisms (copB, cutA1, cutA2, and cutC) in the X. fastidiosa biofilm formed in two different media. We confirmed that biofilms are less susceptible to copper than planktonic cells. The amount of EPS seems to be directly related to the resistance and it varies according to the media where the cells are grown. The same was observed for gene expression. Nevertheless, some genes seem to have a greater importance in biofilm cells resistance to copper. Our results suggest a synergistic effect between diffusion barriers and other mechanisms associated with bacterial resistance in this phytopathogen. These mechanisms are important for a bacterium that is constantly under stress conditions in the host.
木质部难养菌是一种能在不同植物物种中引发疾病的植物病原体。疾病症状的发展与生物膜形成导致的木质部导管堵塞有关。在本研究中，我们评估了生物膜细胞和浮游细胞对铜（农业中使用的最重要抗菌剂之一）的敏感性。我们测量了生物膜细胞和浮游细胞中的胞外多糖（EPS）含量，并使用实时逆转录聚合酶链反应来评估在两种不同培养基中形成的木质部难养菌生物膜中编码参与阳离子/多药外排的蛋白质（acrA/B、mexE/czcA和metI）以及其他与不同铜抗性机制相关的蛋白质（copB、cutA1、cutA2和cutC）的基因的表达。我们证实生物膜比浮游细胞对铜更不敏感。EPS的量似乎与抗性直接相关，并且会根据细胞生长的培养基而变化。基因表达情况也是如此。然而，一些基因似乎在生物膜细胞对铜的抗性中更为重要。我们的结果表明在这种植物病原体中，扩散屏障与其他细菌抗性相关机制之间存在协同效应。这些机制对于在宿主中持续处于应激条件下的细菌来说很重要。
