Abstract
This study compares predicted sulphur metabolism genes across four Acidihalobacter type strains and two metagenome-assembled genomes (MAGs), revealing genomic differences that appear to correspond to ecological specialization. Phylog-enomic analysis separates the species into two clades: clade I includes Acidihalobacter ferrooxydans from a geothermal region in Italy and the two MAGs derived from deep-sea hydrothermal vents in the Pacific Ocean, while clade II comprises Acidihalo-bacter aeolianus and Acidihalobacter prosperus from a geothermal region in Italy and Acidihalobacter yilgarnensis from a saline and acidic drainage in Australia. Variations in sulphide/quinone oxidoreductases (SQRs) across the species, in particular in Ah. ferrooxydans and Ah. yilgarnensis, likely relate to the availability and speciation of sulphur substrates, which are strictly gov-erned by local redox potential (Eh) and metal redox cycling in their respective habitats. Notably, only Ah. ferrooxydans (clade I) lacks the canonical sulphur/thiosulphate oxidation (Sox) system for thiosulphate oxidation found in clade II and instead encodes components of an alternative S4 I pathway. We hypothesize that this difference reflects an adaptation to dynamic microniches going from highly reduced (sulphide-rich) to oxidized metastable sulphur intermediates. In contrast, the retention of the Sox system in clade II suggests a distinct strategy permitting greater metabolic versatility under fluctuating Eh-pH conditions. Differences in clade I terminal oxidases (cbb3-type cytochrome, bc1 complex) and regulatory elements appear to support further adaptation to environments with elevated H2 S, setting this clade apart from clade II members. These adaptations, mainly evi-denced by gene redundancy, gene loss and horizontal gene transfer, seem to reflect a unique ecological microniche and evolutionary trajectory for Ah. ferrooxydans distinct from other members of the genus, particularly from a sulphur-based energy metabolism perspective.
Keywords
acidic adaptation, astrobiology, chalcopyrite bioleaching, comparative genomics, halotolerance, sulphur oxidation
Document Type
Journal Article
Date of Publication
1-1-2026
Article Number
001732
Volume
12
Issue
5
PubMed ID
42200512
Publication Title
Microbial Genomics
Publisher
Microbiology Society
School
School of Science
RAS ID
95304
Funding Information
This work was supported by ANID/BASAL/FB210008 to D.S.H. and ANID (Chilean National Research and Development Agency) ANILLO ATE220007 to J.H.V.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Vergara, E., Khaleque, H. N., Neira, G., Watkin, E. L., Valdés, J. H., & Holmes, D. S. (2026). Sulphur metabolism as a key factor in the evolution of environmental adaptation of Acidihalobacter. Microbial Genomics, 12(5). https://doi.org/10.1099/mgen.0.001732