Rubrobacter xylanophilus sp. nov., a New Thermophilic Species Isolated from a Thermally Polluted Effluent

Abstract

One strain of a thermophilic, slightly halotolerant bacterium was isolated from a thermally polluted industrial runoff near Salisbury, United Kingdom. This organism, strain PRD-lT (T = type strain), for which we propose the name Rubrobacter xylanophilus sp. nov., produces short gram-positive rods and coccoid cells and forms pink colonies. The optimum growth temperature is approximately 60°C. Unusual internal branchedchain fatty acids (namely, 12-methylhexadecanoic acid and 14-methyloctadecanoic acid) make up the major acyl chains of the lipids. The results of our 16s rRNA sequence comparisons showed that strain PRD-lT is related to Rubrobacter radiotolerans and that these two organisms form a deep evolutionary line of descent within the gram-positive Bacteria.Over the past 20 years the microbiology of thermophiles has been dominated by the isolation and characterization of thermophilic Archaea species, many of which grow at extreme temperatures. During this time, however, many new thermophilic Bacteria species, several belonging to the gram-positive phylum, have been isolated from a wide range of thermal environments. The majority of the thermophilic gram-positive Bacteria species that have been described belong to the genera Bacillus, Alicyclobacillus, and Clostridium and other recently proposed genera, some of which were formerly included in the genus Clostridium (3,5,18,28,33,40).The species Rubrobacter radiotolerans, which was initially named Arthrobacter radiotolerans, was described on the basis of one strain isolated from a hot spring in Japan after gamma irradiation of water samples (35,44). R. radiotolerans is gram positive, has an optimum growth temperature of about 48"C, and forms short pleomorphic rod-shaped cells. It is also highly radiotolerant and possesses unique internally branched fatty acids.A pink-pigmented strain was recently isolated from a thermally polluted runoff from a carpet factory in the United Kingdom. This organism is more thermophilic than R. radiotolerans and also possesses unusual branched-chain fatty acids. On the basis of morphological and biochemical characteristics, chemotaxonomic parameters, and 16s rRNA gene sequence data, we propose that this organism, strain PRD-lT (T = type strain), belongs to a new species, Rubrobacter xylanophilus. MATERIALS AND METHODSIsolation of strain PRD-IT. Strain PRD-lT was isolated from thermally polluted runoff (temperature, 50°C) from a carpet factory in Wilton, Wiltshire, United Kingdom. This strain was isolated by spreading a biofilm sample with a glass rod on tryptone soya agar. After incubation at 50°C for 5 days, one pinkpigmented colony appeared on a culture plate and was purified on the same medium. R. radiotolerans DSM 46359T was obtained from the Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany. Strains PRD-lT and DSM 46359T were routinely grown in Thermus medium containing 1.0 g of yeast extract per liter and 1.0 g of tryptone medium (41) per liter and were stored at -80°C in the same medium containing 1...

A Unique Combination of Genetic Systems for the Synthesis of Trehalose in Rubrobacter xylanophilus : Properties of a Rare Actinobacterial TreT

“…In fact, T6P has been found to play important signaling roles in the regulation of sugar metabolism in Saccharomyces cerevisiae, by inhibiting hexokinase, and in Arabidopsis thaliana, where it activates ADP-glucose pyrophosphorylase (27). T6P is also a precursor of complex structures found in actinobacteria, such as mycolic acids, although R. xylanophilus lacks these trehalose-containing structures (5,35). The organization of the TreS and TreY/TreZ genes in a different and unique operon-like structure containing other genes for glycogen metabolism and the lack of activity in cell extracts from cultures grown on tryptone and yeast extract led us to hypothesize that these genes may be expressed only when maltose or maltooligosaccharides are used as carbon sources, as is the case with the TreS from Corynebacterium glutamicum (38).…”

Macroamphiphilic Components of Thermophilic Actinomycetes: Identification of Lipoteichoic Acid in Thermobifida fusca

“…R. xylanophilus is a less intensively studied organism, although its genome sequence has recently been completed and it is of interest with regard to the mechanisms of radiation resistance (4, 10; http://genome .jgi-psf.org/finished_microbes/rubxy/rubxy.home.html). Moreover, the phylogenetic position of the subclass Rubrobacteridae is of interest, because this lineage may represent one of the earliest branches of the class Actinobacteria (4,16,17,30,48). Interestingly, our studies have shown that whereas T. fusca synthesizes a PGP-LTA, the cell envelope of R. xylanophilus appears to lack a macroamphiphile.…”

Organic solutes in Rubrobacter xylanophilus: the first example of di-myo-inositol-phosphate in a thermophile

“…The bacteria of the genus Rubrobacter represent the most ancient lineage of the phylum Actinobacteria (High G + C Gram-positive bacteria) known and are assigned to three known species, namely R. radiotolerans, R. taiwanensis and R. xylanophilus with optimum growth temperatures of 45, 55, and 60°C, respectively (Carreto et al 1996;Chen et al 2004;Suzuki et al 1988). All strains examined of Rubrobacter are gamma-radiation resistant and R. xylanophilus is, not only the most thermophilic actinobacterium known, but also the only true extremely radiation-resistant thermophile (Suzuki et al 1988;Ferreira et al 1999;Chen et al 2004).…”