Downloaded from www.microbiologyresearch.org by IP: 23.22.50.124 On: Fri, 08 Apr 2016 06:14:21 International Journal of Systematic Bacteriology (1998), 48, 1389-1 398 Printed in Great Britain Phylogeny and photosynthetic features of Thiobacillus acidophilus and related acidophilic bacteria : its transfer to the genus Acidiphilium as Acidiphilium acidophilum comb. nov. Akira Hiraishi,’ Kenji V. P. Nagashima,’ Katsumi Matsuura,’ Keizo Shimada,’ Shinichi Takai~hi,~ Norio Wakao4and Yoko Katayama5 Author for correspondence: Akira Hiraishi. Tel: +81 532 44 6913. Fax: +81 532 44 6929. e-mail : hiraishiialeco.tut.ac.jp Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi 441, Japan Department of Biology, Tokyo Metropol ita n University, Hachioji 192-03, Japan B iolog ica I Laboratory, Nippon Medical School, Kawasaki 21 1, Japan Department of Bioscience and Technology, lwate University, Morioka 020, Japan Department of Environmental and Natural Resources Science, Tokyo University of Agriculture and Technology, Fuchu 183, Japan Phylogenetic analyses based on 16s rDNA sequences and genomic DNA-DNA relatedness showed that the sulphur-oxidizing facultative chemolithotroph Thiobacillusacidophilus was closely related to members of the genus Acidiphilium, which is a group of strictly aerobic, heterotrophic acidophiles now categorized into aerobic photosynthetic bacteria. Lipophilic pigment analyses revealed that zinc-chelated bacteriochlorophyll a and carotenoids occurred in appreciable amounts in T. acidophilus and all established species of the genus Acidiphilium. PCR experiments showed that T. acidophilus as well as Acidiphilium species contained puf genes, encoding the photosynthetic reaction centre proteins and the core light-harvesting complex of the purple bacteria. There were high similarities between T. acidophilus and Acidiphilium species in the primary structure of their reaction centre proteins deduced from the nucleotide sequence data. The phylogenetic tree of the reaction centre proteins was in agreement with the 165 rDNA sequence-based phylogenetic tree in the relationship between T. acidophilus and Acidiphilium species and between the Acidiphilium cluster and other purple photosynthetic bacteria. Based on these results, together with previous phylogenetic and phenotypic information, it is proposed to reclassify T. acidophilus (Guay and Silver) Harrison 1983 as Acidiphilium acidophilum comb. nov. The type strain is ATCC 27807T (= DSM 700T). Keywords : Thiobacillus ncidophilus, zinc-bacteriochlorophyll, photosynthetic reaction cent re, phylogeny , Acidiph ilium acidophilum corn b. nov. INTRODUCTION The genus Thiobacillus is a group of obligately or facultatively chemolithotrophic aerobic proteo- bacteria that are capable of growing with reduced inorganic sulphur compounds as sole energy source, but, at this time, is quite heterogeneous with members exhibiting a wide range of physiological, chemo- taxonomic and genetic characteristics (Katayama- Fujimura et a/., 1982, 1983; Kelly & Harrison, 1989; Lane et ul., 1985, 1992). This group encompasses a . .. . . . . . , . ........ . . .. . .. . . . , ... . . . . ,. . . . . .. . . . . . . .. .. . . . .. . . . . . . . . . .. . . . ..... . ...... ..... . . .... . . . . . . . . . . . . . . . . .. . . . . .. . . . . .. . . . . . Abbreviations: BChl, bacteriochlorophyll; BPhe, bacteriopheophytin. The DDBJ accession numbersforthe 165 rDNAsequences determined in this paper are D86508, D86509, D86511, D86513 and AB006712; for the puf gene the number is AB013379. number of acidophilic species (Harrison, 1984 ; Pronk et a/., 1990), including Thiobacillus acidophilus, in addition to neutrophilic thiobacilli. The name T. acidophilus was proposed by Guay & Silver (1975) for some strains of facultatively chemolithotrophic acido- philic thiobacilli, but did not appear on the Approved Lists of Bacterial Names (Skerman et a/., 1980). Harrison (1983) revived the name T . acidophilus following his confirmation that this organism grew equally well with elemental sulphur or glucose as a sole energy source. Phylogenetic analyses based on 5s rRNA sequences (Lane et a/., 1985) and partial 16s rRNA sequences (Lane et a/., 1992), however, indi- cated that T. acidophilus was far distant from any other Thiobacillus species and was closely related to species of the genus Acic~@kilium, which includes aerobic ~- 00819 0 1998 IUMS 1389