Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Tue, 11 Dec 2018 15:20:59 Acidithiobacillus ferridurans sp. nov., an acidophilic iron-, sulfur- and hydrogen-metabolizing chemolithotrophic gammaproteobacterium Sabrina Hedrich and D. Barrie Johnson Correspondence D. Barrie Johnson d.b.johnson@bangor.ac.uk School of Biological Sciences, College of Natural Sciences, Bangor University, Bangor LL57 2UW, UK Twelve strains of iron-oxidizing acidithiobacilli isolated from acidic sites throughout the world, including some previously shown by multi-locus sequence analyses and DNA–DNA hybridization to comprise a distinct species, were characterized in terms of their physiologies. The bacteria were shown to be obligately chemolithotrophic, acidophilic and mesophilic, and grew in both oxic and anoxic environments, using ferrous iron, reduced sulfur or hydrogen as electron donors and oxygen or ferric iron as electron acceptors. Some of the strains grew at lower pH than those reported for the two recognized iron-oxidizing Acidithiobacillus species, Acidithiobacillus ferrooxidans and Acidithiobacillus ferrivorans. Tolerance of transition metals and aluminium, and also specific rates of iron oxidation and reduction, were more similar to those of A. ferrooxidans (to which the strains are more closely related) than to A. ferrivorans. The name Acidithiobacillus ferridurans sp. nov. is proposed to accommodate the 12 strains, with the type strain being JCM 18981 T (5ATCC 33020 T ). The genus Acidithiobacillus includes, at the time of writing, two recognized species that can obtain energy from the oxidation of ferrous iron, Acidithiobacillus ferrooxidans and Acidithiobacillus ferrivorans. Prior to the designation of A. ferrivorans as a distinct species (Hallberg et al., 2010), rod- shaped acidophilic, obligately autotrophic bacteria that catalysed the dissimilatory oxidation of both iron and sulfur were generally classified as strains of A. ferrooxidans, although a number of researchers had highlighted the probability, based on phylogenetic and other analyses, that these bacterial strains represent several distinct species (e.g. Harrison, 1982; Selenska-Pobell et al., 1998, Karavaiko et al., 2003; Peng et al., 2006; Amouric et al., 2011). A multi-locus sequence analysis of 21 strains of iron- oxidizing acidithiobacilli carried out by Amouric et al. (2011) grouped the bacteria into four distinct clusters: Group I included the type strain of A. ferrooxidans (ATCC 23270 T ), Group III included only strains of A. ferrivorans, while bacteria included in Groups II and IV appeared to be strains of two separate and distinct species. One of the ‘Group II’ acidithiobacilli was strain ATCC 33020 T (also referred to as strain 11Fe), which was isolated from water draining from a uranium mine in Japan (Tomizuka et al., 1976). Amouric et al. (2011) noted that DNA–DNA hybridization between A. ferrooxidans ATCC 23270 T and strain ATCC 33020 T was 63 %, while Harrison (1982) had previously reported a figure of 60 % for strains ATCC 33020 T and ATCC 19859 (another ‘Group I’ iron-oxidizing Acidithiobacillus). Both figures are ,70 %, the value used to delineate species (Wayne et al., 1987). Further evidence of separate phylogenetic identities was published by Selenska-Pobell et al. (1998), who found that that ARDREA analysis of the intergenic spacer region between the 16S and 23S rRNA genes of strain ATCC 33020 T produced different digestion profiles from other strains, including A. ferrooxidans ATCC 23270 T . Here we provide confirmatory evidence that strain ATCC 33020 T and related strains comprise a distinct species of the genus Acidithiobacillus. Physiological characteristics of the pro- posed type strain of the species (ATCC 33020 T ) are described. The bacterial strains used in this study are listed in Table 1. Acidithiobacillus sp. ATCC 33020 T and strain CC1 were kindly provided by Dr Violaine Bonnefoy (CNRS, Marseille, France). All other strains listed were sourced from the acidophile culture collection maintained at Bangor University (UK). The latter were designated as belonging to Groups I and II (classification system of Amouric et al., 2011) from sequence analysis of their 16S rRNA genes. Bacteria were grown routinely in pH 1.8 The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of various strains determined in this study are: CF3 (JX442933), 9/11 (JX442934), T22 (JX905219), SJ22 (JX442932), MCF59 (KC257406), S10 (JX442935), WVa2 (JX442943), D2-PG (JX442941), F221 (JX442942), GG6/10 (JX442937), L11 (JX442938), M12 (JX442936), R10 (JX442940), Riv11 (JX442939). Two supplementary figures are available with the online version of this paper. International Journal of Systematic and Evolutionary Microbiology (2013), 63, 4018–4025 DOI 10.1099/ijs.0.049759-0 4018 049759 G 2013 IUMS Printed in Great Britain