Cellular and molecular outcomes of Pseudomonas putida KT2440 exposure to aluminium

Despite being an abundant metal, nature evolved to exclude aluminium (Al) from living organisms. In addition, the complex chemistry of this element makes it a challenging case for researchers. At physiological pH, Al has strong affinity to oxygen donors and negatively charged molecules such as proteins, nucleotides and cellular components bearing phosphates and carboxylic groups. Because of its widespread industrial use, living organisms are increasingly exposed to soluble forms of this light metal and environmental bacteria are in the front line. In this work, we show the disruptive effect of Al at physiological pH on the cellular morphology of Pseudomonas putida KT2440 and on the integrity of its mature biofilms. Proteomic studies revealed that an exposure to 0.78 mM of the aluminium compound used in this study significantly affected key proteins and enzymes involved in the TCA cycle, the respiratory chain, the maintenance of the cell's membrane and the transmembrane transport systems. The expression levels of major metal-resistance proteins (e.g., P-type ATPases and RND tripartite efflux pumps) was not affected, contrary to those of methyltransferases and systems involved in the metabolism of phosphate that might be involved in the maintenance of low Al concentration in the cytoplasm.