Arsukibacterium ikkense gen. nov., sp. nov, a novel alkaliphilic, enzyme-producing γ-Proteobacterium isolated from a cold and alkaline environment in Greenland

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Abstract

A novel aerobic, Gram-negative, non-pigmented bacterium, GCM72T, was isolated from the alkaline, low-saline ikaite columns in the Ikka Fjord, SW Greenland. Strain GCM72T is a motile, non-pigmented, amylase- and protease-producing, oxidase-positive, and catalase-negative bacterium, showing optimal growth at pH 9.2–10.0, at 15 °C, and at 3% (w/v) NaCl. Major fatty acids were C12:0 3-OH (12.2±0.1%), C16:00 (18.0±0.1%), C18:1ω7c (10.7±0.5%), and summed feature 3 comprising C16:1ω7c and/or iso-C15:0 2-OH (36.3±0.7%). Phylogenetic analysis based on 16S rRNA gene sequences showed that isolate GCM72T was most closely related to Rheinheimera baltica and Alishewanella fetalis of the γ-Proteobacteria with a 93% sequence similarity to both. The G+C content of DNA isolated from GCM72T was 49.9 mol% and DNA–DNA hybridization between GCM72 T and R. baltica was 9.5%. Fatty acid analysis and G+C content supports a relationship primarily to R. baltica, but several different features, such as a negative catalase-response and optimal growth at low temperature and high pH, together with the large phylogenetic distance and low DNA similarity to its closest relatives, lead us to propose a new genus, Arsukibacterium, gen. nov., with the new species Arsukibacterium ikkense sp. nov. (type strain is GCM72T).

Introduction

Ikaite tufa columns from the Ikka Fjord, SW Greenland, constitute a rare low-saline (0.9%), alkaline (pH 10.4), and cold (0–4 °C) environment [3]. Previous investigations have shown that the columns harbor a large microbial diversity with a number of alkaliphilic and psychrophilic bacterial species and that up to one-fourth of the species belong to not yet characterized species [13]. One of the prominent bacterial groups was shown to be the γ-Proteobacteria, which constituted 9% of the total bacterial diversity in 16S rRNA gene libraries and more than 40% of the cultured isolates [13]. In this study, we have isolated a novel enzyme-producing γ-Proteobacterium from the interior of an ikaite column from the Ikka Fjord, SW Greenland. The isolated strain, GCM72T, shows phylogenetic relationship to species of the genera Rheinheimera and Alishewanella, but because of the distant phylogenetic relationship and low DNA similarity, and due to several different morphological and physiological features, we propose a novel genus, Arsukibacterium gen. nov., with the new species Arsukibacterium ikkense sp. nov. (DSM 17999=LMG 23455).

Section snippets

Materials and methods

The strain GCM72T was isolated from ikaite tufa columns collected from the Ikka Fjord, SW Greenland (61°11′N, 48°01′W) in 2002. The columns were conserved in 15% glycerol and kept at −20 °C. Bacteria were isolated on agar plates containing a modified, 10 times diluted R2A medium at pH 10 as described by Schmidt et al. [13]. Physiological features were determined using a 10 times diluted R2 broth medium (1/10R2 broth), containing the same ingredients as 1/10R2A except for agar. The 10 times

Results and discussion

Strain GCM72T is a chemoheterotrophic, aerobic, non-pigmented, motile, Gram-negative bacterium. The cells are rods of 2.5–4 μm in length and 0.5–0.8 μm in width, and were observed to multiply by binary division. Colonies are small (0.1–1.5 mm in diameter), circular, smooth, and white to transparent in appearance. The isolate was cytochrome oxidase-positive and catalase-negative.

The growth of strain GCM72T was observed at temperatures from 0 to 30 °C. Growth at 0 °C was approximately 45–50% of the

Description of Arsukibacterium gen. nov.

Arsukibacterium [Ar.su.ki.bac.te’ri.um. Arsuk, a town near the site of origin of the type strain; L. neut. n. bacterium, a stick or staff; N.L. neut. n. Arsukibacterium, a bacterium from Arsuk]. Cells are Gram-negative, motile, rod-shaped, catalase-negative, and cytochrome oxidase-positive. Growth is aerobic, chemoheterotrophic and occurs at temperatures from 0 to 30 °C, with an optimum around 15 °C. Growth occurs best at pH 9–10 and at 3% (w/v) NaCl, but the bacterium can be isolated from

Description of Arsukibacterium ikkense sp. nov.

Arsukibacterium ikkense (ik.ken'se. N.L. neut. adj. ikkense from the Ikka Fjord, referring to the origin of the type strain): cells are oval to straight rods of 2.5–4 μm in length and 0.5–0.8 μm in width, and were observed to multiply by binary division. They typically occur as single cells, but strains of up to eight cells can be observed. Colonies are circular, smooth, and white to transparent. Strains are cytochrome oxidase-positive and catalase-negative, and growth occurs at temperatures from

Acknowledgments

We thank Karin Vestberg for excellent technical skills, Carsten Aarup for doing the biofilm analysis, José Bresciani for scanning electron microscopy, and John Larsen for doing analysis of fatty acids. Referring to the Convention on Biological Diversity, we thank the Greenland Home Rule for permission to sample ikaite columns from the Ikka Fjord, SW Greenland. This work was partly funded by The Commission for Scientific Research in Greenland (PS), the Danish Agency for Trade and Industry (MS

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Note: Nucleotide sequence data reported is available in the GenBank/EMBL/DDBJ databases under the accession number DQ112664.

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