Possible Role of Envelope Components in the Extreme Copper Resistance of the Biomining Acidithiobacillus ferrooxidans.

Alberto Paradela,Sergio Álvarez,Cristóbal Martínez-Bussenius,Claudio Navarro,Carlos Jerez,Rodrigo Norambuena,Nia Oetiker,Fernando Amaya

doi:10.3390/genes9070347

Abstract

Acidithiobacillus ferrooxidans resists extremely high concentrations of copper. Strain ATCC 53993 is much more resistant to the metal compared with strain ATCC 23270, possibly due to the presence of a genomic island in the former one. The global response of strain ATCC 53993 to copper was analyzed using iTRAQ (isobaric tag for relative and absolute quantitation) quantitative proteomics. Sixty-seven proteins changed their levels of synthesis in the presence of the metal. On addition of CusCBA efflux system proteins, increased levels of other envelope proteins, such as a putative periplasmic glucan biosynthesis protein (MdoG) involved in the osmoregulated synthesis of glucans and a putative antigen O polymerase (Wzy), were seen in the presence of copper. The expression of A. ferrooxidans mdoG or wzy genes in a copper sensitive Escherichia coli conferred it a higher metal resistance, suggesting the possible role of these components in copper resistance of A. ferrooxidans. Transcriptional levels of genes wzy, rfaE and wzz also increased in strain ATCC 23270 grown in the presence of copper, but not in strain ATCC 53993. Additionally, in the absence of this metal, lipopolysaccharide (LPS) amounts were 3-fold higher in A. ferrooxidans ATCC 53993 compared with strain 23270. Nevertheless, both strains grown in the presence of copper contained similar LPS quantities, suggesting that strain 23270 synthesizes higher amounts of LPS to resist the metal. On the other hand, several porins diminished their levels in the presence of copper. The data presented here point to an essential role for several envelope components in the extreme copper resistance by this industrially important acidophilic bacterium.

Highlights

Acidithiobacillus ferrooxidans is a gram-negative, acidophilic, chemolithoautotrophic bacterium able to use ferrous iron, reduced species of sulfur or metal sulfides as energy sources [1,2,3,4,5]
The functional categories of all proteins changing in A. ferrooxidans 53993 are shown in Table S1 and Figure S1 and the data obtained is seen in Tables S2 and S3
Copper ATCC 53993 cells grew reaching similar numbers to the control, they were apparently more affected than cells subjected to 100 mM copper since a greater number of proteins related to metabolism and protein biosynthesis decreased their levels whereas others related to energy production and copper resistance increased their amounts

Summary

Introduction

Acidithiobacillus ferrooxidans is a gram-negative, acidophilic, chemolithoautotrophic bacterium able to use ferrous iron, reduced species of sulfur or metal sulfides as energy sources [1,2,3,4,5]. These bacteria are able to grow at high concentrations of several metals. This is an important property since they are used in biomining processes where copper concentrations are in the range of 15 to 100 mM [6,7,8]. The microorganisms forming part of the biomining consortium have developed additional strategies to resist the harsh conditions in which they live, and their study is of great interest [19,20]

Methods

Results

Conclusion