24 November 2020

Unlocking Survival Mechanisms for Metal and Oxidative Stress in the Extremely Acidophilic, Halotolerant Acidihalobacter Genus

DOI : 10.3390/genes11121392


Microorganisms used for the biohydrometallurgical extraction of metals

from minerals must be able to survive high levels of metal and oxidative

stress found in bioleaching environments. The Acidihalobacter

genus consists of four species of halotolerant, iron–sulfur-oxidizing

acidophiles that are unique in their ability to tolerate chloride and

acid stress while simultaneously bioleaching minerals. This paper uses

bioinformatic tools to predict the genes and mechanisms used by Acidihalobacter

members in their defense against a wide range of metals and oxidative

stress. Analysis revealed the presence of multiple conserved mechanisms

of metal tolerance. Ac. yilgarnensis F5T,

the only member of this genus that oxidizes the mineral chalcopyrite,

contained a 39.9 Kb gene cluster consisting of 40 genes encoding mobile

elements and an array of proteins with direct functions in copper

resistance. The analysis also revealed multiple strategies that the Acidihalobacter members can use to tolerate high levels of oxidative stress. Three of the Acidihalobacter

genomes were found to contain genes encoding catalases, which are not

common to acidophilic microorganisms. Of particular interest was a

rubrerythrin genomic cluster containing genes that have a polyphyletic

origin of stress-related functions.

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