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Genes 2018, 9(2), 113; https://doi.org/10.3390/genes9020113

Biofilm Formation by the Acidophile Bacterium Acidithiobacillus thiooxidans Involves c-di-GMP Pathway and Pel exopolysaccharide

1
Bacterial Communication Laboratory, Biology Department, Faculty of Sciences, Universidad de Chile, Ñuñoa 7800003, Santiago, Chile
2
Organic and Environmental Chemistry Laboratory, Faculty of Sciences, Universidad de Chile, Ñuñoa 7800003, Santiago, Chile
*
Author to whom correspondence should be addressed.
Received: 28 December 2017 / Revised: 31 January 2018 / Accepted: 6 February 2018 / Published: 21 February 2018
(This article belongs to the Special Issue Genetics and Genomics of Extremophiles)
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Abstract

Acidophile bacteria belonging to the Acidithiobacillus genus are pivotal players for the bioleaching of metallic values such as copper. Cell adherence to ores and biofilm formation, mediated by the production of extracellular polymeric substances, strongly favors bioleaching activity. In recent years, the second messenger cyclic diguanylate (c-di-GMP) has emerged as a central regulator for biofilm formation in bacteria. C-di-GMP pathways have been reported in different Acidithiobacillus species; however, c-di-GMP effectors and signal transduction networks are still largely uncharacterized in these extremophile species. Here we investigated Pel exopolysaccharide and its role in biofilm formation by sulfur-oxidizing species Acidithiobacillus thiooxidans. We identified 39 open reading frames (ORFs) encoding proteins involved in c-di-GMP metabolism and signal transduction, including the c-di-GMP effector protein PelD, a structural component of the biosynthesis apparatus for Pel exopolysaccharide production. We found that intracellular c-di-GMP concentrations and transcription levels of pel genes were higher in At. thiooxidans biofilm cells compared to planktonic ones. By developing an At. thiooxidans ΔpelD null-mutant strain we revealed that Pel exopolysaccharide is involved in biofilm structure and development. Further studies are still necessary to understand how Pel biosynthesis is regulated in Acidithiobacillus species, nevertheless these results represent the first characterization of a c-di-GMP effector protein involved in biofilm formation by acidophile species. View Full-Text
Keywords: Acidithiobacillus; biofilm; bioleaching; biomining; c-di-GMP; Pel exopolysaccharide; PelD Acidithiobacillus; biofilm; bioleaching; biomining; c-di-GMP; Pel exopolysaccharide; PelD
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Díaz, M.; Castro, M.; Copaja, S.; Guiliani, N. Biofilm Formation by the Acidophile Bacterium Acidithiobacillus thiooxidans Involves c-di-GMP Pathway and Pel exopolysaccharide. Genes 2018, 9, 113.

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