The complete genome of Burkholderia phenoliruptrix strain BR3459a, a symbiont of Mimosa flocculosa: Highlighting the coexistence of symbiotic and pathogenic genes

BMC Genomics

Volumn 15, Issue 1, 2014, Pages

  Zuleta, Luiz F G ^a   Cunha, Claúdio D O ^b,c   de Carvalho, Fabíola M ^a   Ciapina, Luciane P ^a   Souza, Rangel C ^a   Mercante, Fábio M ^d   de Faria, Sergio M ^e   Baldani, José I ^e   Straliotto, Rosangela ^e   Hungria, Mariangela ^d   de Vasconcelos, Ana T R ^a  

^a LABORATÓRIO NACIONAL DE COMPUTAÇÃO CIENTÍFICA   (Brazil)

^b FEDERAL UNIVERSITY OF CEARÁ   (Brazil)

^c Ministério de Ciência Tecnologia e Inovação Salvador   (Brazil)

^d EMBRAPA CERRADOS   (Brazil)

^e EMBRAPA AGROBIOLOGIA   (Brazil)

Author keywords

Burkholderia phenoliruptrix; Comparative genomics; Nitrogen fixing and pathogenic Burkholderia

Indexed keywords

CAPROLACTAM; CHLOROBENZENE; CHLOROCYCLOHEXANE; CYCLOHEXANE DERIVATIVE; DIOXIN; EXOPOLYSACCHARIDE; NITROTOLUENE; NOVOBIOCIN; STREPTOMYCIN; STYRENE; TOLUENE DERIVATIVE; UNCLASSIFIED DRUG; BACTERIAL PROTEIN; VIRULENCE FACTOR;

ANTIBIOTIC RESISTANCE; ARTICLE; BACTERIAL GENE; BACTERIAL GENOME; BACTERIAL GROWTH; BACTERIAL STRAIN; BCE GENE; BRAZIL; BURKHOLDERIA; BURKHOLDERIA PHENOLIRUPTRIX; BURKHOLDERIA PHYMATUM; COLD STRESS; CONTROLLED STUDY; ENVIRONMENTAL STRESS; HEAT STRESS; HOUSEKEEPING GENE; LEGUME; MIMOSA FLOCCULOSA; NITROGEN FIXATION; NONHUMAN; NUCLEOTIDE SEQUENCE; OSMOTIC STRESS; PLASMID; SPECIES COEXISTENCE; SYMBIOSIS; TYPE I SECRETION SYSTEM; TYPE II SECRETION SYSTEM; TYPE III SECRETION SYSTEM; TYPE IV SECRETION SYSTEM; TYPE VI SECRETION SYSTEM; XENOBIOTIC METABOLISM; BACTERIAL SECRETION SYSTEM; DNA SEQUENCE; GENETICS; MICROBIOLOGY; MIMOSA; PHENOTYPE; PHYLOGENY; SYNTENY;

BURKHOLDERIA; BURKHOLDERIA CEPACIA COMPLEX; BURKHOLDERIA PHENOLIRUPTRIX; BURKHOLDERIA PHYMATUM; MIMOSA FLOCCULOSA; PSEUDOMALLEI GROUP;

BACTERIAL PROTEINS; BACTERIAL SECRETION SYSTEMS; BURKHOLDERIA; DRUG RESISTANCE, BACTERIAL; GENOME, BACTERIAL; MIMOSA; NITROGEN FIXATION; PHENOTYPE; PHYLOGENY; PLASMIDS; SEQUENCE ANALYSIS, DNA; SYMBIOSIS; SYNTENY; VIRULENCE FACTORS;

EID: 84902938296     PISSN: None     EISSN: 14712164     Source Type: Journal    
DOI: 10.1186/1471-2164-15-535     Document Type: Article

References (82)

1. Vial L, Chapalain A, Groleau MC, Deziel E. The various lifestyles of the Burkholderia cepacia complex species: a tribute to adaptation. Environ Microbiol 2011, 13:1-12.
2. Coenye T, Vandamme P. Diversity and significance of Burkholderia species occupying diverse ecological niches. Environ Microbiol 2003, 5:719-729.
3. Coenye T, Vandamme P, Govan JRW, Lipuma JJ. Taxonomy and identification of the Burkholderia cepacia complex. J Clin Microbiol 2001, 39:3427-3436.
4. Bontemps C, Elliott GN, Simon MF, Dos Reis FBD, Gross E, Lawton RC, Neto NE, Loureiro MD, De Faria SM, Sprent JI, James EK, Young JPW. Burkholderia species are ancient symbionts of legumes. Mol Ecol 2010, 19:44-52.
5. Gyaneshwar P, Hirsch AM, Moulin L, Chen WM, Elliott GN, Bontemps C, Estrada-de Los Santos P, Gross E, Dos Reis FB, Sprent JI, Young JP, James EK. Legume-nodulating betaproteobacteria: diversity, host range, and future prospects. Mol Plant Microbe Interact 2011, 24:1276-1288.
6. Ormeno-Orrillo E, Rogel MA, Chueire LMO, Tiedje JM, Martinez-Romero E, Hungria M. Genome Sequences of Burkholderia sp Strains CCGE1002 and H160, Isolated from Legume Nodules in Mexico and Brazil. J Bacteriol 2012, 194:6927-6927.
7. Suarez-Moreno ZR, Caballero-Mellado J, Coutinho BG, Mendonca-Previato L, James EK, Venturi V. Common features of environmental and potentially beneficial plant-associated Burkholderia. Microb Ecol 2012, 63:249-266.
8. Gautam V, Singhal L, Ray P. Burkholderia cepacia complex: Beyond pseudomonas and acinetobacter. Indian J Med Microbiol 2011, 29:4-12.
9. Govan JR, Vandamme P. Agricultural and medical microbiology: a time for bridging gaps. Microbiology 1998, 144(Pt 9):2373-2375.
10. Burkholder WH. Sour skin, a bacterial rot of onion bulbs. Phytopathology 1950, 40:115-117.
11. Yabuuchi E, Kosako Y, Oyaizu H, Yano I, Hotta H, Hashimoto Y, Ezaki T, Arakawa M. Proposal of Burkholderia gen. nov. and transfer of seven species of the genus Pseudomonas homology group II to the new genus, with the type species Burkholderia cepacia (Palleroni and Holmes 1981) comb. nov. Microbiol Immunol 1992, 36:1251-1275.
12. Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures [http://www.dsmz.de/microorganisms/pnu/bacterial_nomenclature_info_mm.php?genus=Burkholderia].
13. Mahenthiralingam E, Baldwin A, Dowson CG. Burkholderia cepacia complex bacteria: opportunistic pathogens with important natural biology. J Appl Microbiol 2008, 104:1539-1551.
14. Goris J, De Vos P, Caballero-Mellado J, Park J, Falsen E, Quensen JF, Tiedje JM, Vandamme P. Classification of the biphenyl- and polychlorinated biphenyl-degrading strain LB400T and relatives as Burkholderia xenovorans sp. nov. Int J Syst Evol Microbiol 2004, 54:1677-1681.
15. Rodrigues JLM, Kachel CA, Aiello MR, Quensen JF, Maltseva OV, Tsoi TV, Tiedje JM. Degradation of Aroclor 1242 dechlorination products in sediments by Burkholderia xenovorans LB400(ohb) and Rhodococcus sp strain RHA1(fcb). Appl Environ Microbiol 2006, 72:2476-2482.
16. Estrada-De Los Santos P, Bustillos-Cristales R, Caballero-Mellado J. Burkholderia, a genus rich in plant-associated nitrogen fixers with wide environmental and geographic distribution. Appl Environ Microbiol 2001, 67:2790-2798.
17. Holmes A, Govan J, Goldstein R. Agricultural use of Burkholderia (Pseudomonas) cepacia: A threat to human health?. Emerg Infect Dis 1998, 4:221-227.
18. Ormeno-Orrillo E, Hungria M, Martinez-Romero E. Dinitrogen-fixing prokaryotes. The Prokaryotes - prokaryotic physiology and biochemistry 2013, 427-451. Berlin Heidelberg: Springer, Rosemberg E, De Long EF, Lory S, Stackebrandt E, Thompson F, 11.
19. Chen WM, Laevens S, Lee TM, Coenye T, De Vos P, Mergeay M, Vandamme P. Ralstonia taiwanensis sp nov., isolated from root nodules of Mimosa species and sputum of a cystic fibrosis patient. Int J Syst Evol Microbiol 2001, 51:1729-1735.
20. Moulin L, Munive A, Dreyfus B, Boivin-Masson C. Nodulation of legumes by members of the beta-subclass of Proteobacteria. Nature 2001, 411:948-950.
21. Bournaud C, De Faria SM, Dos Santos JMF, Tisseyre P, Silva M, Chaintreuil C, Gross E, James EK, Prin Y, Moulin L. Burkholderia Species are the most common and preferred nodulating symbionts of the piptadenia group (tribe mimoseae). PLoS One 2013, 8:e63478.
22. Chen WM, Moulin L, Bontemps C, Vandamme P, Bena G, Boivin-Masson C. Legume symbiotic nitrogen fixation by beta-proteobacteria is widespread in nature. J Bacteriol 2003, 185:7266-7272.
23. Menna P, Hungria M, Barcellos FG, Bangel EV, Hess PN, Martinez-Romero E. Molecular phylogeny based on the 16S rRNA gene of elite rhizobial strains used in Brazilian commercial inoculants. Syst Appl Microbiol 2006, 29:315-332.
24. Vandamme P, Goris J, Chen WM, De Vos P, Willems A. Burkholderia tuberum sp. nov. and Burkholderia phymatum sp. nov., nodulate the roots of tropical legumes. Syst Appl Microbiol 2002, 25:507-512.
25. Mishra RPN, Tisseyre P, Melkonian R, Chaintreuil C, Miche L, Klonowska A, Gonzalez S, Bena G, Laguerre G, Moulin L. Genetic diversity of Mimosa pudica rhizobial symbionts in soils of French Guiana: investigating the origin and diversity of Burkholderia phymatum and other beta-rhizobia. Fems Microbiol Ecol 2012, 79:487-503.
26. Talbi C, Argandona M, Salvador M, Alche JD, Vargas C, Bedmar EJ, Delgado MJ. Burkholderia phymatum improves salt tolerance of symbiotic nitrogen fixation in Phaseolus vulgaris. Plant Soil 2013, 367:673-685.
27. Coenye T, Henry D, Speert DP, Vandamme P. Burkholderia phenoliruptrix sp nov., to accommodate the 2,4,5-trichlorophenoxyacetic acid and halophenol-degrading strain AC1100. Syst Appl Microbiol 2004, 27:623-627.
28. Cunha CO, Zuleta LFG, De Almeida LGP, Ciapina LP, Borges WL, Pitard RM, Baldani JI, Straliotto R, De Faria SM, Hungria M, Cavada BS, Mercante FM, De Vasconcelos ATR. Complete genome sequence of Burkholderia phenoliruptrix BR3459a (CLA1), a heat-tolerant, nitrogen-fixing symbiont of mimosa flocculosa. J Bacteriol 2012, 194:6675-6676.
29. Cunha CO. Rhizobia nodulating Phaseolus vulgaris and legume trees: study of some aspects dealing with heat tolerance and nodulation control 1992, Katholieke Universiteit Leuven, Belgium: Master's thesis.
30. Leitao JH, Sousa SA, Ferreira AS, Ramos CG, Silva IN, Moreira LM. Pathogenicity, virulence factors, and strategies to fight against Burkholderia cepacia complex pathogens and related species. Appl Microbiol Biotechnol 2010, 87:31-40.
31. Zhu B, Zhou S, Lou M, Zhu J, Li B, Xie G, Jin G, De Mot R. Characterization and inference of gene gain/loss along burkholderia evolutionary history. Evol Bioinform Online 2011, 7:191-200.
32. Mousavi SA, Ósterman J, Wahlberg N, Nesme X, Lavire C, Vial L, Paulin L, De Lajudie P, Lindström K. Phylogeny of the Rhizobium-Allorhizobium-Agrobacterium clade supports the delineation of Neorhizobium gen. nov. Syst Appl Microbiol 2014, http://dx.doi.org/10.1016/j.syapm.2013.12.007.
33. Nierman WC, DeShazer D, Kim HS, Tettelin H, Nelson KE, Feldblyum T, Ulrich RL, Ronning CM, Brinkac LM, Daugherty SC, Davidsen TD, Deboy RT, Dimitrov G, Dodson RJ, Durkin AS, Gwinn ML, Haft DH, Khouri H, Kolonay JF, Madupu R, Mohammoud Y, Nelson WC, Radune D, Romero CM, Sarria S, Selengut J, Shamblin C, Sullivan SA, White O, Yu Y, et al. Structural flexibility in the Burkholderia mallei genome. Proc Natl Acad Sci U S A 2004, 101:14246-14251.
34. Kim HS, Schell MA, Yu Y, Ulrich RL, Sarria SH, Nierman WC, DeShazer D. Bacterial genome adaptation to niches: Divergence of the potential virulence genes in three Burkholderia species of different survival strategies. BMC Genomics 2005, 6:174.
35. Ferreira AS, Silva IN, Oliveira VH, Cunha R, Moreira LM. Insights into the role of extracellular polysaccharides in Burkholderia adaptation to different environments. Front Cell Infect Microbiol 2011, 1:16.
36. Hallack LF, Passos DS, Mattos KA, Agrellos OA, Jones C, Mendonca-Previato L, Previato JO, Todeschini AR. Structural elucidation of the repeat unit in highly branched acidic exopolysaccharides produced by nitrogen fixing Burkholderia. Glycobiology 2010, 20:338-347.
37. Cerantola S, Lemassu-Jacquier A, Montrozier H. Structural elucidation of a novel exopolysaccharide produced by a mucoid clinical isolate of Burkholderia cepacia - Characterization of a trisubstituted glucuronic acid residue in a heptasaccharide repeating unit. Eur J Biochem 1999, 260:373-383.
38. Cescutti P, Bosco M, Picotti F, Impallomeni G, Leitao JH, Richau JA, Sa-Correia I. Structural study of the exopolysaccharide produced by a clinical isolate of Burkholderia cepacia. Biochem Biophys Res Commun 2000, 273:1088-1094.
39. Ferreira AS, Leitao JH, Silva IN, Pinheiro PF, Sousa SA, Ramos CG, Moreira LM. Distribution of cepacian biosynthesis genes among environmental and clinical Burkholderia strains and role of cepacian exopolysaccharide in resistance to stress conditions. Appl Environ Microbiol 2010, 76:441-450.
40. Ferreira AS, Leitao JH, Sousa SA, Cosme AM, Sa-Correia I, Moreira LM. Functional analysis of Burkholderia cepacia genes bceD and bceF, encoding a phosphotyrosine phosphatase and a tyrosine autokinase, respectively: Role in exopolysaccharide biosynthesis and biofilm formation. Appl Environ Microbiol 2007, 73:524-534.
41. Vanhaverbeke C, Heyraud A, Mazeau K. Conformational analysis of the exopolysaccharide from Burkholderia caribensis strain MWAP71: impact on the interaction with soils. Biopolymers 2003, 69:480-497.
42. Delepelaire P. Type I secretion in gram-negative bacteria. Biochim Biophys Acta 2004, 1694:149-161.
43. Peabody CR, Chung YJ, Yen MR, Vidal-Ingigliardi D, Pugsley AP, Saier MH. Type II protein secretion and its relationship to bacterial type IV pili and archaeal flagella. Microbiology 2003, 149:3051-3072.
44. Vignon G, Köhler R, Larquet E, Giroux S, Prévost MC, Roux P, Pugsley AP. Type IV-like pili formed by the type II secreton: specificity, composition, bundling, polar localization, and surface presentation of peptides. J Bacteriol 2003, 185:3416-3428.
45. Cianciotto NP. Type II secretion: a protein secretion system for all seasons. Trends Microbiol 2005, 13:581-588.
46. Gophna U, Ron EZ, Graur D. Bacterial type III secretion systems are ancient and evolved by multiple horizontal-transfer events. Gene 2003, 312:151-163.
47. Voth DE, Broederdorf LJ, Graham JG. Bacterial Type IV secretion systems: versatile virulence machines. Future Microbiol 2012, 7:241-257.
48. Alvarez-Martinez CE, Christie PJ. Biological diversity of prokaryotic type IV secretion systems. Microbiol Mol Biol Rev 2009, 73:775-808.
49. Vincent CD, Friedman JR, Jeong KC, Buford EC, Miller JL, Vogel JP. Identification of the core transmembrane complex of the Legionella Dot/Icm type IV secretion system. Mol Microbiol 2006, 62:1278-1291.
50. Dautin N, Bernstein HD. Protein secretion in gram-negative bacteria via the autotransporter pathway. Annu Rev Microbiol 2007, 61:89-112.
51. Silverman JM, Brunet YR, Cascales E, Mougous JD. Structure and regulation of the type vi secretion system. Annu Rev Microbiol 2012, 66:453-472.
52. Hengge-Aronis R. Signal transduction and regulatory mechanisms involved in control of the sigma(S) (RpoS) subunit of RNA polymerase. Microbiol Mol Biol Rev 2002, 66:373-395. table of contents.
53. Wood JM. Bacterial osmosensing transporters. Methods Enzymol 2007, 428:77-107.
54. Wood JM. Bacterial osmoregulation: a paradigm for the study of cellular homeostasis. Annu Rev Microbiol 2011, 65:215-238.
55. Agre P, Sasaki S, Chrispeels MJ. Aquaporins: a family of water channel proteins. Am J Physiol 1993, 265:F461.
56. Guisbert E, Yura T, Rhodius VA, Gross CA. Convergence of molecular, modeling, and systems approaches for an understanding of the Escherichia coli heat shock response. Microbiol Mol Biol Rev 2008, 72:545-554.
57. Yamanaka K, Fang L, Inouye M. The CspA family in Escherichia coli: multiple gene duplication for stress adaptation. Mol Microbiol 1998, 27:247-255.
58. Battesti A, Majdalani N, Gottesman S. The RpoS-mediated general stress response in Escherichia coli. Annu Rev Microbiol 2011, 65:189-213.
59. Hengge-Aronis R. Signal transduction and regulatory mechanisms involved in control of the σS (RpoS) subunit of RNA polymerase. Microbiol Mol Biol Rev 2002, 66:373-395.
60. Weber H, Polen T, Heuveling J, Wendisch VF, Hengge R. Genome-wide analysis of the general stress response network in Escherichia coli: σS-dependent genes, promoters, and sigma factor selectivity. J Bacteriol 2005, 187:1591-1603.
61. Maynaud G, Willems A, Soussou S, Vidal C, Maure L, Moulin L, Cleyet-Marel JC, Brunel B. Molecular and phenotypic characterization of strains nodulating Anthyllis vulneraria in mine tailings, and proposal of Aminobacter anthyllidis sp nov., the first definition of Aminobacter as legume-nodulating bacteria. Syst Appl Microbiol 2012, 35:65-72.
62. Ardley JK, Parker MA, De Meyer SE, Trengove RD, O'Hara GW, Reeve WG, Yates RJ, Dilworth MJ, Willems A, Howieson JG. Microvirga lupini sp nov., Microvirga lotononidis sp nov and Microvirga zambiensis sp nov are alphaproteobacterial root-nodule bacteria that specifically nodulate and fix nitrogen with geographically and taxonomically separate legume hosts. Int J Syst Evol Micr 2012, 62:2579-2588.
63. Ormeno-Orrillo E, Menna P, Almeida LGP, Ollero FJ, Nicolas MF, Rodrigues EP, Nakatani AS, Batista JSS, Chueire LMO, Souza RC, Vasconcelos ATR, Megias M, Hungria M, Martinez-Romero E. Genomic basis of broad host range and environmental adaptability of Rhizobium tropici CIAT 899 and Rhizobium sp PRF 81 which are used in inoculants for common bean (Phaseolus vulgaris L.). BMC Genomics 2012, 13:735.
64. Gottfert M, Grob P, Hennecke H. Proposed regulatory pathway encoded by the nodV and nodW genes, determinants of host specificity in Bradyrhizobium japonicum. Proc Natl Acad Sci U S A 1990, 87:2680-2684.
65. Godoy LP, Vasconcelos ATR, Chueire LMO, Souza RC, Nicolas MF, Barcellos FG, Hungria M. Genomic panorama of Bradyrhizobium japonicum CPAC 15, a commercial inoculant strain largely established in Brazilian soils and belonging to the same serogroup as USDA 123. Soil Biol Biochem 2008, 40:2743-2753.
66. Kaneko T, Maita H, Hirakawa H, Uchiike N, Minamisawa K, Watanabe A, Sato S. Complete genome sequence of the soybean symbiont Bradyrhizobium japonicum strain USDA6T. Genes (Basel) 2011, 2:763-787.
67. Gonzalez V, Santamaria RI, Bustos P, Hernandez-Gonzalez I, Medrano-Soto A, Moreno-Hagelsieb G, Janga SC, Ramirez MA, Jimenez-Jacinto V, Collado-Vides J, Davila G. The partitioned Rhizobium etli genome: Genetic and metabolic redundancy in seven interacting replicons. Proc Natl Acad Sci U S A 2006, 103:3834-3839.
68. Menard A, Monnez C, Santos PEDL, Segonds C, Caballero-Mellado J, LiPuma JJ, Chabanon G, Cournoyer B. Selection of nitrogen-fixing deficient Burkholderia vietnamiensis strains by cystic fibrosis patients: involvement of nif gene deletions and auxotrophic mutations. Environ Microbiol 2007, 9:1176-1185.
69. Karns JS, Kilbane JJ, Duttagupta S, Chakrabarty AM. Metabolism of halophenols by 2,4,5-trichlorophenoxyacetic acid degrading Pseudomonas-Cepacia. Appl Environ Microbiol 1983, 46:1176-1181.
70. Ussery DW, Kiil K, Lagesen K, Sicheritz-Ponten T, Bohlin J, Wassenaar TM. The genus Burkholderia: analysis of 56 genomic sequences. Genome Dyn 2009, 6:140-157.
71. Moore RA, DeShazer D, Reckseidler S, Weissman A, Woods DE. Efflux-mediated aminoglycoside and macrolide resistance in Burkholderia pseudomallei. Antimicrob Agents Chemother 1999, 43:465-470.
72. Angus AA, Agapakis CM, Fong S, Yerrapragada S, Estrada-de Los Santos P, Yang P, Song N, Kano S, Caballero-Mellado J, De Faria SM, Dakora FD, Weinstock G, Hirsch AM. Plant-associated symbiotic Burkholderia species lack hallmark strategies required in mammalian pathogenesis. PLoS One 2014, 9:e83779.
73. Vincent JM. Manual for the Practical Study of Root-Nodule Bacteria 1970, Oxford (UK): Blackwell Scientific.
74. Almeida LG, Paixao R, Souza RC, Costa GC, Barrientos FJ, Santos MT, Almeida DF, Vasconcelos AT. A system for automated bacterial (genome) integrated annotation-SABIA. Bioinformatics 2004, 20:2832-2833.
75. Overbeek R, Fonstein M, D'Souza M, Pusch GD, Maltsev N. The use of gene clusters to infer functional coupling. Proc Natl Acad Sci U S A 1999, 96:2896-2901.
76. Altschul SF, Madden TL, Schaffer AA, Zhang J, Zhang Z, Miller W, Lipman DJ. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Res 1997, 25:3389-3402.
77. Petkau A, Stuart-Edwards M, Stothard P, Van Domselaar G. Interactive microbial genome visualization with GView. Bioinformatics 2010, 26:3125-3126.
78. Cole JR, Wang Q, Cardenas E, Fish J, Chai B, Farris RJ, Kulam-Syed-Mohideen AS, McGarrell DM, Marsh T, Garrity GM, Tiedje JM. The Ribosomal Database Project: improved alignments and new tools for rRNA analysis. Nucleic Acids Res 2009, 37:D141-D145.
79. Notredame C, Higgins DG, Heringa J. T-Coffee: A novel method for fast and accurate multiple sequence alignment. J Mol Biol 2000, 302:205-217.
80. Tamura K, Peterson D, Peterson N, Stecher G, Nei M, Kumar S. MEGA5: Molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods. Mol Biol Evol 2011, 28:2731-2739.
81. Juhas M, Stark M, Von Mering C, Lumjiaktase P, Crook DW, Valvano MA, Eberl L. High confidence prediction of essential genes in burkholderia cenocepacia. PLoS One 2012, 7:e40064.
82. Thompson JD, Gibson TJ, Plewniak F, Jeanmougin F, Higgins DG. The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res 1997, 25:4876-4882.