Short Report

Acidophilic haloarchaeal strains are isolated from various solar salts

Hiroaki Minegishi¹ , Toru Mizuki¹ , Akinobu Echigo¹ , Tadamasa Fukushima¹ , Masahiro Kamekura² and Ron Usami¹

¹  Bio-Nano Electronics Research Center, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585, Japan

²  Halophiles Research Institute, 677-1 Shimizu, Noda, Chiba 278-0043, Japan

author email corresponding author email

Saline Systems 2008, 4:16doi:10.1186/1746-1448-4-16

Published:	29 October 2008

Abstract

Haloarchaeal strains require high concentrations of NaCl for their growth, with optimum concentrations of 10–30%. They display a wide variety of morphology and physiology including pH range for growth. Many strains grow at neutral to slightly alkaline pH, and some only at alkaline pH. However, no strain has been reported to grow only in acidic pH conditions within the family Halobacteriaceae.

In this study, we isolated many halophiles capable of growth in a 20% NaCl medium adjusted to pH 4.5 from 28 commercially available salts. They showed growth at pH 4.0 to 6.5, depending slightly on the magnesium content. The most acidophilic strain MH1-52-1 isolated from an imported solar salt (pH of saturated solution was 9.0) was non-pigmented and extremely halophilic. It was only capable of growing at pH 4.2–4.8 with an optimum at pH 4.4 in a medium with 0.1% magnesium chloride, and at pH 4.0–6.0 (optimum at pH 4.0) in a medium with 5.0% magnesium. The 16S rRNA and DNA-dependent RNA polymerase subunit B' gene sequences demonstrated clearly that the strain MH1-52-1 represents a new genus in the family Halobacteriaceae.