Acidithiobacillus ferrianus sp. nov.: an ancestral extremely acidophilic and facultatively anaerobic chemolithoautotroph

Paul R Norris,Ana Moya-Beltrán,D Barrie Johnson,Carmen Falagán,Matías Castro,Raquel Quatrini

doi:10.1007/s00792-020-01157-1

Abstract

Strain MG, isolated from an acidic pond sediment on the island of Milos (Greece), is proposed as a novel species of ferrous iron- and sulfur-oxidizing Acidithiobacillus. Currently, four of the eight validated species of this genus oxidize ferrous iron, and strain MG shares many key characteristics with these four, including the capacities for catalyzing the oxidative dissolution of pyrite and for anaerobic growth via ferric iron respiration. Strain MG also grows aerobically on hydrogen and anaerobically on hydrogen coupled to ferric iron reduction. While the 16S rRNA genes of the iron-oxidizing Acidi-thiobacillus species (and strain MG) are located in a distinct phylogenetic clade and are closely related (98–99% 16S rRNA gene identity), genomic relatedness indexes (ANI/dDDH) revealed strong genomic divergence between strain MG and all sequenced type strains of the taxon, and placed MG as the first cultured representative of an ancestral phylotype of iron oxidizing acidithiobacilli. Strain MG is proposed as a novel species, Acidithiobacillus ferrianus sp. nov. The type strain is MGT (= DSM 107098T = JCM 33084T). Similar strains have been found as isolates or indicated by cloned 16S rRNA genes from several mineral sulfide mine sites.

Highlights

The genus Acidithiobacillus [phylum Proteobacteria, class Acidithiobacillia
Some acidithiobacilli can use hydrogen as sole electron donor, but while this appears to be a common trait for all strains of some species (A. ferrooxidans and A. ferridurans) this is not the case for strains of other species (A. ferrivorans, A. thiooxidans and A. caldus) and has not been observed in any strain of A. ferriphilus (Hedrich and Johnson 2013b; Falagán and Johnson 2016)
Ferrous iron oxidation was observed in a ferrous iron enrichment culture of sediment from the pond margin and ferric iron-encrusted colonies were readily obtained on Phytagel-solidified medium containing 25 mM ferrous iron at pH 2

Summary

Introduction

The genus Acidithiobacillus [phylum Proteobacteria, class Acidithiobacillia All of these species can grow autotrophically using zero-valent (elemental) sulfur and sulfide, and sulfur-oxyanions that are more reduced than sulfate, as electron donors. We describe strain MG, isolated from an acidic pond on the island of Milos (Greece), which represents a novel, ancestral phylotype of iron-oxidizing acidithiobacilli (phylotype 3A of Nuñez et al 2017) and we present chemotaxonomic and genomic taxonomy data to support its recognition as a fifth iron oxidizing species, A. ferrianus MGT

Materials and methods

Results and discussion

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