Unraveling the Central Role of Sulfur-Oxidizing Acidiphilium multivorum LMS in Industrial Bioprocessing of Gold-Bearing Sulfide Concentrates

Abstract

Acidiphilium multivorum LMS is an acidophile isolated from industrial bioreactors during the processing of the gold-bearing pyrite-arsenopyrite concentrate at 38–42 °C. Most strains of this species are obligate organoheterotrophs that do not use ferrous iron or reduced sulfur compounds as energy sources. However, the LMS strain was identified as one of the predominant sulfur oxidizers in acidophilic microbial consortia. In addition to efficient growth under strictly heterotrophic conditions, the LMS strain proved to be an active sulfur oxidizer both in the presence or absence of organic compounds. Interestingly, Ac. multivorum LMS was able to succeed more common sulfur oxidizers in microbial populations, which indicated a previously underestimated role of this bacterium in industrial bioleaching operations. In this study, the first draft genome of the sulfur-oxidizing Ac. multivorum was sequenced and annotated. Based on the functional genome characterization, sulfur metabolism pathways were reconstructed. The LMS strain possessed a complicated multi-enzyme system to oxidize elemental sulfur, thiosulfate, sulfide, and sulfite to sulfate as the final product. Altogether, the phenotypic description and genome analysis unraveled a crucial role of Ac. multivorum in some biomining processes and revealed unique strain-specific characteristics, including the ars genes conferring arsenic resistance, which are similar to those of phylogenetically distinct microorganisms.

Microbes of biotechnological importance in acidic saline lakes in the Yilgarn Craton, Western Australia

“…The most abundant Acidiphilium ASV in Lakes 1 and 3 water samples had the highest identity to A. multivorum (97.96 and 98.41%, respectively), an acidophilic, gram-negative, chemoorganotrophic sulfur-oxidizing bacteria that was isolated from AMD in Japan ( Wakao et al, 1994 ). This genus has been hypothesized to be used in the production of acetic acid, is metal-resistant, and has also been identified as an extremely active sulfur oxidizer in industrial bioreactors leaching gold from pyrite–arsenopyrite concentrates ( Micciche et al, 2020 ; Panyushkina et al, 2021 ). Salinisphaeraceae was another family in high abundance in the salt brine and water samples and consisted exclusively of the Salinisphaera genus, which is an aerobic facultative chemolithoautotrophic halophile and has been isolated from slightly acidic environments ( Crespo-Medina et al, 2009 ; O’Dell et al, 2018 ).…”

The third symbiotic partner of the volcano lichenCladonia vulcaniSavicz drove adaptation to an extreme environment

“…BlastN searches of assembled contigs against the NCBI database indicated that LFB_Cvu01 is similar to bacteria of the genus Acidiphilium, some species of which were reported to have sulfur-oxidizing ability (48,49). Sulfur-oxidizing bacteria can use sulfide or various reduced inorganic sulfur compounds as sources of energy to synthesize organic compounds.…”

The Evaluation of Bacterial Abundance and Functional Potentials in the Three Major Watersheds, Located in the Hot Spring Zone of the Tatun Volcano Group Basin, Taiwan

“…The higher expression of sulfur oxide-related pathways in the HGC is responsible for the oxidation of sulfide and thiosulfate to sulfate, which is used as an energy source [ 86 ]. Likewise, Acidiphilium , which is dominant in the HGC, exhibits the bifunctional enzyme CysN/CysC, which is one of the components of the assimilatory sulfate reduction pathways involved in reducing sulfate to sulfide [ 87 ]. The bifunctional enzyme, sulfane dehydrogenase subunit SO X C, which is significantly enriched in the HGC samples, is often associated with thermophilic bacterial communities that catalyze the reduction of elemental sulfur to hydrogen sulfide [ 88 ].…”