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Department of Biology, University of Bergen, Jahnebakken 5, 5020 Bergen, Norway
Correspondence
Jørn Einen
jorn.einen{at}bio.uib.no
| ABSTRACT |
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| MAIN TEXT |
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Samples of basaltic pillow lavas were collected from the sea floor during the SUBMAR 2001 cruise to the Jan Mayen platform in the Norwegian/Greenland Sea (71° 04' 38'' N 7° 29' 6'' W). The samples were collected by dredging at a depth of 1300 m. The sea floor temperature at the sampling site was 0.7 °C. Immediately after the samples were on deck, the outer glassy rim of the pillow basalt was chipped off. The glass was added to sterile seawater and stored in closed 100 ml flasks in darkness for 3 years at 10 °C. Subsamples were plated onto marine broth 2216 (Difco; MB) with 1.5 % agar, and incubated at 10 °C. After 14 days incubation, four yellow colonies were picked. Strains from these four colonies (designated H32, H33, H34 and H35T) were purified, and preserved in MB supplemented with 15 % glycerol at 80 °C.
Unless stated otherwise the strains were grown in Flavobacteriaceae medium (FM; 30 g Sigma sea salts l1, 5 g D-glucose l1, 0.5 g yeast extract l1, adjusted to pH 8.0) at a temperature of 22 °C. Gram staining, oxidase, catalase and alkaline phosphatase tests were performed as described by Smibert & Krieg (1994)
. The ability of the strains to hydrolyse agar, gelatin, chitin, cellulose (CF11 powder; Whatman), starch, urea, aesculin and DNA was examined according to the procedures of Smibert & Krieg (1994)
. Hydrolysis of L-tyrosine was examined as described by Collins (1995)
. Hydrolysis of Tweens was examined as described by Slifkin (2000)
. The hydrolysis tests were performed on MB + 1.5 % agar (MA) medium at an incubation temperature of 15 °C. FM supplemented with cysteine.HCl to a final concentration of 0.05 % was used to examine the ability of the strains to produce H2S from cysteine (Smibert & Krieg, 1994
). FM without glucose and with 0.15 % phenol red was used to test for the production of acids from a variety of sugars supplemented to a final concentration of 1 %. FM with appropriate modifications was used to examine the requirement for growth factors.
Temperature, pH and salinity range and optimum were examined by measuring growth in 96-well microtitre plates. Growth was measured as OD630. To determine the temperature range for growth, the strains were grown in MB. For pH determination, the strains were grown in FM supplemented with 50 mM buffer. The following buffer systems (pH range) were used: citric acid (3.54.0), acetic acid (4.55.5), PIPES (6.07.4), HEPES (7.68.0) and Tris (8.210.5). For the salinity experiments, FM with different sea salt concentrations was used. The strains were tested for fermentative growth on MB and FM. To test for anaerobic respiration, MB and FM supplemented with NaNO3, Fe(III) citrate or amorphous Mn(IV) oxide to 0.2 % were used. The anaerobic medium was flushed with N2 immediately after autoclaving to remove O2. The medium was then supplemented with NaHCO3 to a final concentration of 0.5 % (w/v) to help facilitate anaerobic growth (Reichenbach, 1989
).
Substrate use was examined using Biolog GN2 plates as described by the manufacturer except that the plates were inoculated with cells grown on MA, and suspended in 1.5 % Sigma sea salts to an OD590 of
0.3. The plates were incubated at 15 °C and manually read after 14 days incubation. The ability of the strains to use methanol, ethanol, 2-propanol or glycerol as sole carbon and energy sources was tested using FM as described, but without D-glucose, as the base medium. The medium was then supplemented with the appropriate alcohol to a final concentration of 1 %.
DNA was isolated using the method described by Marmur (1963)
. DNA G+C content was determined by the thermal denaturation method (Mandel et al., 1970
). Fatty acid methyl ester and quinone analyses were carried out by the Identification Service of the DSMZ (Braunschweig, Germany).
16S rRNA genes from the four strains were PCR amplified, sequenced and assembled to a 1422-bp-long fragment by using standard methods. Percentage sequence similarity between the basalt strains and the type species of genera in the the family Flavobacteriaceae was determined by the global alignment program MATGAT (Campanella et al., 2003
). Closely related sequences were selected for generation of phylogenetic trees using the neighbour-joining, maximum-likelihood and maximum-parsimony algorithms. The neighbour-joining tree was constructed in CLUSTAL_X (Thompson et al., 1997
) and bootstrap values were calculated based on 1000 replications. Maximum-likelihood and maximum-parsimony trees were constructed in PHYLIP (Felsenstein, 2004
).
Pigments were extracted from cells grown without light in MB using ethanol. The cellular residues were removed by centrifugation. An adsorption spectrum (175900 nm) was obtained from the crude cell extract using a Cary 4E UVvisible spectrophotometer (Varian). Cell pigments were also extracted using acetone, and separated by TLC using cellulose-covered plastic plates (Merck) and petroleum ether/acetone (9 : 1) as the chromatographic liquid. The separated pigments were cut out and extracted in acetone. An adsorption spectrum (390700 nm) was obtained from the separated pigments using a UV mini 1240 spectrophotometer (Shimadzu). Cellulophaga lytica DSM 7489T was used as a reference in the pigment analysis (Lewin & Lounsbery, 1969
). To detect flexirubin-type pigments, the bathochromic shift test with 20 % (w/v) KOH (Reichenbach, 1989
) was performed.
Phenotypic and genotypic analysis could not differentiate the four strains H32, H33, H34 and H35T. The 16S rRNA gene sequences from the four strains were also identical.
Cells in exponential growth phase were rod-shaped, with a diameter of 0.20.3 µm and a length of 13 µm. Cells in stationary phase were pleomorphic with a diameter of 0.20.3 µm and lengths ranging from 1 to 30 µm. In stationary-phase cultures, branched and curled cells were also observed (Fig. 1
). As cultures aged, cells degenerated into spheroplasts ranging from 0.15 to 0.5 µm in diameter (Fig. 1
). After 1 month incubation under optimum conditions, nearly all cells had degenerated into spheroplasts, which were found to be non-viable. The strains must, however, be able to survive for at least 3 years at 10 °C on seawater and basalt given that they could be cultivated from the inoculum. Cells displayed gliding motility. Motility was best observed in fresh cultures grown in FM with <0.05 % yeast extract. No spreading growth was observed on MA or FM plates. Cells were observed by microscopy to be motile by polar adhesion to the glass slide, with a rotational movement of about 3 rotations s1. Cells gripped the surface at the opposite pole and then released at the first pole. This behaviour has been described previously for members of the family Flavobacteriaceae (Lapidus & Berg, 1982
). Polar appendage structures (Fig. 2
) were observed by scanning electron microscopy on many of the cells that were motile. These structures were not observed on non-motile cells.
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-,
- and
-hydroxybutyric acid, ketovaleric acid, acetic acid, adonitol, bromosuccinic acid, cis-aconitic acid, citric acid, D-alanine, D-arabitol, D-galactonic acid lactone, D-gluconic acid, D-glucosaminic acid, D-mannitol, D-melibiose, D-psicose, D-saccharic acid, D-sorbitol, formic acid, glucuronamide, hydroxy-L-proline, i-erythritol, itaconic acid, L-alaninamide, L-alanine, L-alanyl glycine, L-arabinose, L-asparagine, L-fucose, L-histidine, L-leucine, L-phenylalanine, L-pyroglutamic acid, malonic acid, myo-inositol, N-acetyl-D-galactosamine, p-hydroxyphenylacetic acid, propionic acid, quinic acid, sebacic acid and xylitol. Further phenotypic characteristics are given in the species description.
Flexirubin-type pigments were not detected. Crude cell extracts from the strains had identical adsorption spectra to that of Cellulophaga lytica with peaks at 264, 334, 451 and 478 nm and a shoulder at 425 nm. Two pigments with typical carotenoid-like spectra were separated by TLC of acetone extract. One orange pigment had adsorption peaks at 451, 477 and 503 nm, and one yellow pigment had adsorption peaks at 431 and 451 nm and a shoulder at 475 nm. The chromatography profile and adsorption patterns of pigments from the basaltic strains were identical to those of C. lytica. C. lytica pigments are identified as zeaxanthin (Aasen & Ljaaen, 1966
; Lewin & Lounsbery, 1969
). The mean DNA G+C content of the four new strains was 31.4±0.6 mol% (SD). The cellular fatty acid profile of strain H35T is summarized in Table 1
. The predominant fatty acids were 15 : 0 iso, 15 : 1 iso, 15 : 0 iso 3-OH and 17 : 0 iso 3-OH. The branched fatty acids accounted for 89 % of all identified fatty acids. The quinone analysis showed that 99 % of the quinones were menaquinone-6 and 1 % menaquinone-7.
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Based on these results, we suggest that the four strains should be included in the family Flavobacteriaceae (Bernardet et al., 2002
) as representatives of a novel species in a new genus, for which the name Flaviramulus basaltis gen. nov., sp. nov. is proposed.
Description of Flaviramulus gen. nov.
Flaviramulus (Fla.vi.ra'mu.lus. L. adj. flavus yellow; L. masc. nom. n. ramulus small branch, dim. of ramus branch or of things having a branching form; N.L. masc. n. Flaviramulus small yellow branch).
Cells are Gram-negative. Morphology varies with age of culture. Cells in exponential growth phase are rods, 0.20.3 µm in diameter and 13 µm in length. Cells in stationary phase are pleomorphic, 0.20.3 µm in diameter but with lengths ranging from 1 to 30 µm. Branched and curled cells are also seen in stationary-phase cultures. As cultures age, cells degenerate into spheroplasts ranging from 0.15 to 1 µm in diameter. Cells are motile, obligately aerobic heterotrophs. Cells contain yellow and orange carotenoids. Flexirubin-type pigments are not found. Menaquinone-6 is the major respiratory quinone. Phylogenetically, this is a member of the family Flavobacteriaceae, class Flavobacteria, phylum Bacteroidetes. The type and only species is Flaviramulus basaltis.
Description of Flaviramulus basaltis sp. nov.
Flaviramulus basaltis (ba.sal'tis. L. masc. gen. n. basaltis of basalt, pertaining to the source of isolation).
Has the following properties in addition to those given for the genus. Colonies grown on MA are shiny, dark yellow, circular, convex, with an entire margin. Cells are catalase-positive, oxidase-negative and alkaline phosphatase-positive. Growth occurs from 2.0 to 34.0 °C, with optimum growth at 17.522.8 °C. The salinity range for growth is 360 g sea salts l1, with an optimum of 2460 g l1. Growth is supported at pH 6.58.6, with optimum growth at pH 6.58.2. Requires seawater, yeast extract or thiamine and amino acids for growth. Utilizes and produces acids from several sugars. Utilizes organic acids and amino acids. Does not utilize alcohols. Hydrolyses L-tyrosine, aesculin, carrageenan, gelatin, starch, DNA, urea, and Tweens 20, 40 and 80, but not agar, cellulose or chitin. Produces H2S from cysteine. Mean DNA G+C content is 31.4±0.6 mol% (SD) as determined by the thermal denaturation method. Branched fatty acids are predominant.
The type strain, H35T (=CIP 109091T=DSM 18180T), was isolated from seafloor basalt offshore of Jan Mayen in the Norwegian/Greenland Sea at a depth of 1300 m.
| ACKNOWLEDGEMENTS |
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