|
|
||||||||
1 Department of Microbiology, University of Hawaii, 2538 The Mall, Honolulu, HI 96822, USA
2 School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania, 7001, Australia
Correspondence
Maqsudul Alam
alam{at}hawaii.edu
| ABSTRACT |
|---|
|
|
|---|
The GenBank accession number for the 16S rRNA gene sequence of LA1T is AF513434.
Scanning electron micrographs of Psychroflexus tropicus cells and growth curves in relation to salinity are available as supplementary material in IJSEM Online.
| MAIN TEXT |
|---|
|
|
|---|
Water from 0·3 m depth at the centre of L. Laysan (25° 46' N 171° 44' W) was spread on marine agar (MA) (Difco) and incubated at 25 °C. An orange colony (LA1) that arose after 5 days was transferred to MA for purification and incubated at 30 °C. Strain LA1T was thence maintained on MA or in marine broth (MB) (Difco). Stock cultures were stored at 80 °C in MB with 30 % glycerol (w/v). Initial identification of LA1T, based on a fragment of the 16S rRNA gene, showed that the strain's closest neigbours are in the genus Psychroflexus, which contains obligate psychrophiles and psychrotolerant [Flavobacterium] gondwanense (Bowman et al., 1998
). LA1T is the first mesophilic Psychroflexus species to be identified.
The tolerance to NaCl of LA1T was tested on tryptic soy agar (TSA) (BBL) with 0·520 % (w/v) NaCl, and on 50 % MA with 120 % (w/v) NaCl, both at 30 °C for 10 days. The 50 % MA was half-strength MA diluted with distilled water, but supplemented with agar to 1·3 % (w/w). The optimum salinity for growth was determined in 50 % MB, in the range 120 % (w/v) NaCl, incubated with shaking (100 r.p.m.) at 30 °C. The 50 % MB was half-strength MB. MB (8·5 ml) was inoculated with 50 µl of a 72 h, 30 °C culture in MB containing 2 % (w/v) NaCl. Growth was followed by measuring the turbidity at
605 of 100 µl subsamples, over 85 h, in a Beckman DU650 spectrophotometer. The growth temperature range was determined on MA from 4 to 60 °C. Anaerobic growth was checked on MA in the BBL GasPak Pouch system, with oxygen and carbon dioxide concentrations of <2 % and >4 %, respectively.
Motility was observed by hanging drop under a 1000x objective with oil immersion after 24 h in MB, or from colonies on MA (7·5 %, w/v, NaCl) in sterile 7·5 % (w/v) saline. Flexirubin-type pigments were checked for by flooding colonies with 20 % KOH (Reichenbach, 1989
). Single colonies on MA were tested for catalase and cytochrome oxidase c with 3 % hydrogen peroxide (Sigma) and tetramethyl-p-phenylenediamine (BBL), respectively. Nitrate reduction was determined in nitrate broth (Difco) containing NaCl to 7·5 % (w/v); standard reagents for reductase were added after 48 h at 30 °C. Amylase was tested on starch medium (Difco) with NaCl concentrations of 07·5 % (w/v) by flooding inoculated plates with iodine after 7 days incubation at 30 °C. Hydrolysis of DNA was checked on DNase test agar with methyl green (Difco), and hydrolysis of gelatin in gelatin nutrient medium (Difco), each in the presence of 1 and 7 % (w/v) NaCl.
Growth on and acidification of carbohydrates in API 50 CH (bioMérieux Vitek) were followed over 5 days in CHB/E medium with SL-8 trace elements solution (Atlas, 1997
), rather than Cohen-Bazire mineral base, and 7·5 % (w/v) NaCl. Constitutive enzyme activities were assayed in API ZYM. Oxidation of carbohydrates, alcohols, organic acids, amino acids and nucleosides as single carbon sources was checked in Biolog GN. Fatty acids in whole cells grown on MA (15 and 30 °C) were analysed in the MIDI system (Sasser, 1997
). Cells grown for 24 h and 5 days in MB were prepared for scanning electron microscopy (Donachie et al., 2002
).
Genomic DNA was extracted from 48 h cultures in MB using the G NOME kit (Qbiogene). A fragment of the 16S rRNA gene was amplified from the DNA by PCR with Pfu DNA polymerase and primers 27F and 1492R (Lane, 1991
). Thermal cycling conditions comprised initial denaturation at 94 °C for 3 min, followed by 30 cycles of 94 °C for 45 s, 55 °C for 1 min, and 72 °C for 90 s. Final extension was carried out at 72 °C for 7 min, followed by cooling to 4 °C. The PCR product was purified with a Qiagen PCR purification kit (Qiagen) and sequenced in both directions in a Beckman CEQ2000 DNA analyser using the Beckman sequencing kit with primers 27F, 519R, 533F and 1492R (Lane, 1991
). 16S rDNA sequences were assembled in Seqman (DNASTAR). Genomic DNA extracted with phenol/chloroform (Marmur, 1961
) from LA1T grown in MB was hybridized with DNA from the type strains of P. torquis and Psychroflexus gondwanensis (Huß et al., 1983
; Bowman et al., 1998
). Hybridizations were carried out in 2x SSC buffer, with renaturation at 64 °C with P. torquis DNA (assuming 32 and 35 mol% G+C, for P. torquis and LA1T, respectively), and at 65 °C with P. gondwanensis DNA (assuming 36 and 35 mol% G+C, for P. gondwanensis and LA1T, respectively). The G+C content of the DNA was determined following Sly et al. (1986)
. The relationship of LA1T with other Bacteria was visualized on the basis of their 16S rRNA gene sequences in a phylogenetic tree constructed from a CLUSTAL X alignment (Thompson et al., 1997
), using the neighbour-joining method (Saitou & Nei, 1987
) corrected for multiple substitutions, and rerooted in NJPlot (Perrière & Gouy, 1996
).
Morphological, physiological and biochemical characteristics of LA1T are given in the species description. In addition, LA1T did not produce flexirubin-type pigments. Coccoid bodies developed in older cultures (see Supplementary Fig. A in IJSEM Online). Although LA1T appeared non-motile in a hanging-drop preparation, the eroded aspect of colony margins might indicate gliding motility (Bernardet et al., 2002
). LA1T grew on TSA only in the presence of 7·5 or 10 % (w/v) NaCl, while growth on MA covered the 120 % salinity range. Differences in growth on these media with the same NaCl concentrations may reflect a requirement for yeast extract, since this is absent from TSA (Bowman et al., 1998
). NaCl-supplemented TSA also lacks other inorganic salts found in MA or MB, a valid consideration because L. Laysan contains evaporated sea water. The salinity optimum for P. tropicus LA1T (see Supplementary Fig. B in IJSEM Online) is greater than that for P. torquis ACAM 623T (optimum 3 %) and P. gondwanensis (5 %). LA1T required 7·5 % (w/v) NaCl in the medium for some activities: nitrate and nitrite reduction took place only in the presence of 7·5 % (w/v) NaCl; there was weak amylase activity on starch plates containing 7·5 % (w/v) NaCl, but not on those with 0, 2 or 4 % (w/v) NaCl; and substrates in Biolog GN were oxidized only when cells were inoculated in 7·5 % (w/v) NaCl. In this respect, it is notable that the salinity in L. Laysan was 7·6 %, as measured by an AGE model 2100 Minisal salinometer calibrated against IAPSO standard (Wormley) sea water. The halophilic and mesophilic nature of LA1T (growth on MA at 43 °C, but not at 50 °C), compared with its nearest Psychroflexus neighbours, confirms the phenotypic diversity, a probable consequence of adaptation, that may occur among phylogenetically close bacteria (Bowman et al., 1998
).
LA1T produced acid from carbohydrates (Table 1
) and expressed constitutive lipolytic, proteolytic and saccharolytic enzymes in API ZYM. The dominant fatty acid changed with incubation temperature (Table 2
). Monounsaturated fatty acids were a greater fraction of the total fatty acid pool at 15 than 30 °C. Iso-branched acids (i15 : 0, i15 : 1, 3-OH i17 : 0) comprised much of the fatty acids in LA1T, while anteiso-branched fatty acids (e.g. a15 : 0, a15 : 1, 3-OH a17 : 0) dominate in other Psychroflexus species (Bowman et al., 1998
). The ratio of anteiso- to iso-branched fractions changed with temperature, with a
3·5-fold increase in this ratio when cells were grown at 15 °C compared to that at 30 °C. The fact that monounsaturated straight-chain fatty acids were essentially lacking is consistent with the description of Psychroflexus.
|
|
|
Gram-negative, non-motile, straight to slightly curved rods 0·180·25 µm wide and 2·02·5 µm long. Old cultures in MB produce coccoid bodies. Orange, circular, butyrous, convex, opaque, entire, smooth, glistening colonies of 24 mm diameter on MA. Gliding motility. Grows aerobically on MA between 4 and 43 °C, but not at 50 °C, and on 50 % strength MA with 120 % (w/v) NaCl. Moderately halophilic, with optimal growth in 50 % strength MB at 30 °C with 7·510 % (w/v) NaCl. No growth on MA in a CO2-enriched atmosphere at 30 °C. Catalase positive, oxidase negative; nitrate reductase expressed in the presence of 7·5 % (w/v) NaCl, but not in the absence of NaCl or with 3·2 % (w/v) NaCl. Other characteristics are listed in Table 1
. Alkaline phosphatase, esterase (C4), esterase lipase (C8), lipase (C14), leucine, valine and cystine arylamidases, trypsin, chymotrypsin, acid phosphatase and phosphohydrolase activities expressed in API ZYM. L-Alanine, L-alanyl glycine, L-asparagine, L-aspartic acid, L-glutamic acid, L-leucine, L-ornithine, L-proline, L-serine, L-threonine, mono-methyl succinate and L-alaninamide are oxidized in Biolog GN in the presence of 7·5 % (w/v) NaCl, but not in the presence of 2 or 4 % (w/v) NaCl. Grows on glycerol, D-glucose, D-fructose, D-mannose, sorbitol, trehalose, starch and D-arabitol in API 50 CH strips. Acid produced from sucrose and 5-ketogluconate. The dominant fatty acids at 15 and at 30 °C are 12-methyl tetradecanoic acid and 13-methyl tetradecanoic acid, respectively. The G+C content is 35±0·8 mol%.
The type strain, LA1T (=ATCC BAA-734T=DSM 15496T), was isolated from water collected at a depth of 0·3 m in hypersaline L. Laysan on Laysan Island in the Northwestern Hawaiian Islands. On the basis of the 16S rDNA sequence, Psychroflexus torquis ACAM 623T from Antarctic sea-ice is the closest described relative (94·4 % sequence identity over 1423 bases). LA1T and P. torquis ACAM 623T share morphological and nutritional traits, but the fact that LA1T grows well at temperatures above 20 °C, together with genotypic differences, support the placement of LA1T as a novel species in Psychroflexus as Psychroflexus tropicus sp. nov.
| ACKNOWLEDGEMENTS |
|---|
| REFERENCES |
|---|
|
|
|---|
Bernardet, J. F., Nakagawa, Y. & Holmes, B. (2002). Proposed minimal standards for describing new taxa of the family Flavobacteriaceae and emended description of the family. Int J Syst Evol Microbiol 52, 10491070.[Abstract]
Bowman, J. P., McCammon, S. A., Lewis, T., Skerratt, J. H., Brown, J. L., Nichols, D. S. & McMeekin, T. A. (1998). Psychroflexus torquis gen. nov., sp. nov., a psychrophilic species from Antarctic sea ice, and reclassification of Flavobacterium gondwanense (Dobson et al., 1993
) as Psychroflexus gondwanense gen. nov., comb. nov. Microbiology 144, 16011609.
Dobson, S. J., Colwell, R. R., McMeekin, T. A. & Franzmann, P. D. (1993). Direct sequencing of the polymerase chain reaction-amplified 16S rRNA gene of Flavobacterium gondwanense sp. nov. and Flavobacterium salegens sp. nov., two new species from a hypersaline Antarctic lake. Int J Syst Bacteriol 43, 7783.
Donachie, S. P., Christenson, B. W., Kunkel, D. D., Malahoff, A. & Alam, M. (2002). Microbial community in acidic hydrothermal waters of volcanically active White Island, New Zealand. Extremophiles 6, 419425.[CrossRef][Medline]
Huß, V. A. R., Festl, H. & Schleifer, K. H. (1983). Studies on the spectrophotometric determination of DNA hybridization from renaturation rates. Syst Appl Microbiol 4, 184192.
Lane, D. J. (1991). 16S/23S rRNA sequencing. In Nucleic Acid Techniques in Bacterial Systematics, pp. 115175. Edited by E. Stackebrandt & M. Goodfellow. Chichester: Wiley.
Manz, W., Wendt-Potthoff, K., Neu, T. R., Szewzyk, U. & Lawrence, J. R. (1999). Phylogenetic composition, spatial structure, and dynamics of lotic bacterial biofilms investigated by fluorescence in situ hybridization and confocal laser scanning microscopy. Microb Ecol 37, 225237.[CrossRef][Medline]
Marmur, J. (1961). A procedure for the isolation of deoxyribonucleic acid from microorganisms. J Mol Biol 3, 208218.
Page, R. D. M. (1996). TREEVIEW: an application to display phylogenetic trees on personal computers. Comput Appl Biosci 12, 357358.
Perrière, G. & Gouy, M. (1996). WWW-Query: an on-line retrieval system for biological sequence banks. Biochimie 78, 364369.[Medline]
Ravenschlag, K., Sahm, K. & Amann, R. (2001). Quantitative molecular analysis of the microbial community in marine Arctic sediments (Svalbard). Appl Environ Microbiol 67, 387395.
Reichenbach, H. (1989). Order I. Cytophagales Leadbetter 1974. In Bergey's Manual of Systematic Bacteriology, vol. 3, pp. 20112013. Edited by J. T. Staley, M. P. Bryant, N. Pfennig & J. G. Holt. Baltimore: Williams & Wilkins.
Saitou, N. & Nei, M. (1987). The neighbor-joining method: a new method for reconstructing phylogenetic trees. Mol Biol Evol 4, 406425.[Abstract]
Sasser, M. (1997). Identification of bacteria by gas chromatography of cellular fatty acids. MIDI Technical Note 101. Newark, DE: MIDI Inc.
Sly, L. I., Blackall, L. L., Kraat, P. C., Tian-Shen, T. & Sangkhobol, V. (1986). The use of second derivative plots for the determination of mol% guanine plus cytosine of DNA by the thermal denaturation method. J Microbiol Methods 5, 139156.
Thompson, J. D., Gibson, T. J., Plewniak, F., Jeanmougin, F. & Higgins, D. G. (1997). The CLUSTAL X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res 25, 48764882.
Wayne, L. G., Brenner, D. J., Colwell, R. R. & 9 other authors (1987). Report of the ad hoc committee on reconciliation of approaches to bacterial systematics. Int J Syst Bacteriol 37, 463464.
This article has been cited by other articles:
![]() |
Y.-G. Chen, X.-L. Cui, Y.-X. Wang, S.-K. Tang, Y.-Q. Zhang, W.-J. Li, J.-H. Liu, Q. Peng, and L.-H. Xu Psychroflexus sediminis sp. nov., a mesophilic bacterium isolated from salt lake sediment in China Int J Syst Evol Microbiol, March 1, 2009; 59(3): 569 - 573. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Laybourn-Parry and D. A Pearce The biodiversity and ecology of Antarctic lakes: models for evolution Phil Trans R Soc B, December 29, 2007; 362(1488): 2273 - 2289. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. A. Mikucki and J. C. Priscu Bacterial Diversity Associated with Blood Falls, a Subglacial Outflow from the Taylor Glacier, Antarctica Appl. Envir. Microbiol., June 15, 2007; 73(12): 4029 - 4039. [Abstract] [Full Text] [PDF] |
||||
![]() |
Z.-P. Liu, B.-J. Wang, X. Dai, X.-Y. Liu, and S.-J. Liu Zhouia amylolytica gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from sediment of the South China Sea Int J Syst Evol Microbiol, December 1, 2006; 56(12): 2825 - 2829. [Abstract] [Full Text] [PDF] |
||||
![]() |
Q. L. Wu, G. Zwart, M. Schauer, M. P. Kamst-van Agterveld, and M. W. Hahn Bacterioplankton Community Composition along a Salinity Gradient of Sixteen High-Mountain Lakes Located on the Tibetan Plateau, China Appl. Envir. Microbiol., August 1, 2006; 72(8): 5478 - 5485. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. T. Khan, Y. Nakagawa, and S. Harayama Sandarakinotalea sediminis gen. nov., sp. nov., a novel member of the family Flavobacteriaceae. Int J Syst Evol Microbiol, May 1, 2006; 56(Pt 5): 959 - 963. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. P. Donachie, J. P. Bowman, and M. Alam Nesiotobacter exalbescens gen. nov., sp. nov., a moderately thermophilic alphaproteobacterium from an Hawaiian hypersaline lake. Int J Syst Evol Microbiol, March 1, 2006; 56(Pt 3): 563 - 567. [Abstract] [Full Text] [PDF] |
||||
![]() |
J.-H. Yoon, S.-J. Kang, S.-Y. Jung, H. W. Oh, and T.-K. Oh Gaetbulimicrobium brevivitae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from a tidal flat of the Yellow Sea in Korea Int J Syst Evol Microbiol, January 1, 2006; 56(1): 115 - 119. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. C. K. Lau, M. M. Y. Tsoi, X. Li, I. Plakhotnikova, S. Dobretsov, M. Wu, P.-K. Wong, J. R. Pawlik, and P.-Y. Qian Stenothermobacter spongiae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from a marine sponge in the Bahamas, and emended description of Nonlabens tegetincola Int J Syst Evol Microbiol, January 1, 2006; 56(1): 181 - 185. [Abstract] [Full Text] [PDF] |
||||
![]() |
J.-H. Yoon, S.-J. Kang, C.-H. Lee, and T.-K. Oh Donghaeana dokdonensis gen. nov., sp. nov., isolated from sea water Int J Syst Evol Microbiol, January 1, 2006; 56(1): 187 - 191. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. C. K. Lau, M. M. Y. Tsoi, X. Li, I. Plakhotnikova, S. Dobretsov, P.-K. Wong, J. R. Pawlik, and P.-Y. Qian Nonlabens tegetincola gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from a microbial mat in a subtropical estuary Int J Syst Evol Microbiol, November 1, 2005; 55(6): 2279 - 2283. [Abstract] [Full Text] [PDF] |
||||
![]() |
H.-Y. Weon, B.-Y. Kim, S.-W. Kwon, I.-C. Park, I.-B. Cha, B. J. Tindall, E. Stackebrandt, H. G. Truper, and S.-J. Go Leadbetterella byssophila gen. nov., sp. nov., isolated from cotton-waste composts for the cultivation of oyster mushroom Int J Syst Evol Microbiol, November 1, 2005; 55(6): 2297 - 2302. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. P. Donachie, J. P. Bowman, S. L. W. On, and M. Alam Arcobacter halophilus sp. nov., the first obligate halophile in the genus Arcobacter Int J Syst Evol Microbiol, May 1, 2005; 55(3): 1271 - 1277. [Abstract] [Full Text] [PDF] |
||||
![]() |
O. I. Nedashkovskaya, S. B. Kim, A. M. Lysenko, G. M. Frolova, V. V. Mikhailov, K. H. Lee, and K. S. Bae Description of Aquimarina muelleri gen. nov., sp. nov., and proposal of the reclassification of [Cytophaga] latercula Lewin 1969 as Stanierella latercula gen. nov., comb. nov. Int J Syst Evol Microbiol, January 1, 2005; 55(1): 225 - 229. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | MICROBIOLOGY | J GEN VIROL |
| J MED MICROBIOL | ALL SGM JOURNALS | |