1887

Chapter 13 : “Stable” Genomes

MyBook is a cheap paperback edition of the original book and will be sold at uniform, low price.

Preview this chapter:
Zoom in
Zoomout

“Stable” Genomes, Page 1 of 2

| /docserver/preview/fulltext/10.1128/9781555818180/9781555811518_Chap13-1.gif /docserver/preview/fulltext/10.1128/9781555818180/9781555811518_Chap13-2.gif

Abstract:

This chapter evaluates the present knowledge about the degree of stability of the genome of enteric bacteria. It discusses about the forces which have contributed to maintaining stability, and considers the types of rearrangements which can and do occur even in those genomes generally considered to be stable. With the use of methods of physical analysis of DNA, and especially the introduction of the use of pulsed-field gel electrophoresis (PFGE), used first in by Smith and colleagues, the genomes of many strains were determined and conservation of gene order was shown to be the rule. It talks about two modifications of PFGE methods, which allow the determination of genome structure in many strains, have been used in representative enteric bacteria. It focuses on the forces which would be expected to act in a conservative way to maintain gene order. It is possible that transspecies recombination due to conjugation or transduction followed by homologous recombination, though very rare, is so important that colinearity is an important advantage. The author concludes that the overall conservation of gene order within the enteric bacteria which was reported many years ago in comparisons of and has been confirmed by the analysis of the physical maps of many strains of and other enteric bacteria determined by PFGE and by the comparison of nucleotide sequences.

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Highlighted Text: Show | Hide
Loading full text...

Full text loading...

Figures

Image of FIGURE 1
FIGURE 1

Comparison of the genomic maps for the endonuclease and positions of selected genes determined by analysis of the locations of insertions of Tn in LT2 ( ) and Ty2 ( ). The arrows beside the operons indicate the direction of transcription. There are three types of rearrangements in with respect to . (i) The arc with arrowheads at both ends indicates a segment of the Ty2 genome within the I- I-A fragment which is inverted relative to LT2. (ii) The open arrows indicate three regions in which the intervals between homologous genes are much longer in than in these are postulated to be insertions of DNA (pathogenicity islands), (iii) The I- I fragments, which are in the order ABCDEFG in (and most others enteric bacteria studied), are in the order AGCEFDB in , presumably due to homologous recombination among the operons.

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of FIGURE 2
FIGURE 2

Separation by PFGE of fragments from I- I digestion of DNA from independent wild-type strains of from the SARA set of strains ( ), taken from Fig. 1 of reference . The lanes marked LT2 represent DNA from strain LT2 (which is SARA2); other lanes show the number of the strain from the SARA set. The normal I- I fragments and their sizes in kilobases are shown as single letters on the right. Unusual bands for a few of the strains are indicated on the left, along with their sizes. Some of the partial digestion products, such as D+E and E + F, are shown on the right; these show that the fragment order is DEF.

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of FIGURE 3
FIGURE 3

Inversions covering the region (adapted from Fig. 6 of reference ). The open vertical bar and genes on the left (S.tm) show the order of genes in LT2, with the positions of these genes shown in kilobases ( ). The shorter bars to the right indicate segments of the chromosomes of (S.en) ( ), (S.ty) ( ), and K-12 (E.co) ( ), which are inverted. The hatched horizonal lines join homologous genes. (equivalent to ) and (equivalent to ) indicate the locations of replication termination in K-12 ( ).

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of FIGURE 4
FIGURE 4

(A) Partial digestion of DNA of independent strains of S. with the endonuclease I-, separation by PFGE, and staining with ethidium bromide (from Fig. 2 of reference ). Lanes: 1, strain 26T4; 2, strain 26T9; 3, strain 26T12; 4, strain 26T19; 5, strain 26T38; 6, strain 26T48, 7, strain 26T49. (B) The fragments shown in panel A are indicated by bars, and their sizes and the fragments they are inferred to include are labelled on the left.

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of FIGURE 5
FIGURE 5

The order of I I fragments in 127 strains of 5. and in other enteric bacteria, showing 26 different genome types (adapted from Fig. 2 of reference ). The order of I- I fragments B to G was determined from data of the type shown in Fig. 2 . The order of I I fragments from strain Ty2 (genomic type 9) had been previously determined by analysis with Tn insertions ( ). The same order was confirmed by partial I I digestion (as shown in Fig. 3 ). The I I fragment joins the left ends of the fragments shown to the right end, forming circles, but their orientations are not known. The orientations of fragments B, D, E, F, and G can be inferred from the polarities of the operons. The solid dots in the I- I fragments indicate the location of . The number of strains of each genome type is shown; some of the theoretical genome types were not detected. The order and sizes of the fragments between operons were previously determined for K-12 ( ), ( ), S. ? ( ), and LT2 ( ). These are illustrated at the bottom, drawn to scale, and all have the same order of fragments as genome type 1 of .

Citation: Sanderson K, McClelland M, Liu S. 1999. “Stable” Genomes, p 217-233. In Charlebois R (ed), Organization of the Prokaryotic Genome. ASM Press, Washington, DC. doi: 10.1128/9781555818180.ch13
Permissions and Reprints Request Permissions
Download as Powerpoint

References

/content/book/10.1128/9781555818180.chap13
1. Anderson, R. P.,, and J. R. Roth. 1978. Gene duplication in bacteria: alteration of gene dosage by sister chromosome exchange. Cold Spring Harbor Symp. Quant. Biol. 43: 1083 1087.
2. Anderson, R. P.,, and J. R. Roth. 1981. Spontaneous tandem genetic duplications in Salmonella typhimurium arise by unequal recombination between ribosomal RNA ( rrn) cistrons. Proc. Natl. Acad. Sci. USA 78: 3113 3117.
3. Bachmann, B. J. 1990. Linkage map of Escherichia coli K-12, edition 8. Microbiol. Rev. 54: 130 197.
4. Beltran, P.,, S. A. Plock,, N. H. Smith,, T. S. Whittam,, D. C. Old,, and R. K. Selander. 1991. Reference collection of strains of the Salmonella typhimurium complex from natural populations. J. Gen. Microbiol. 137: 601 606.
5. Berlyn, M. B.,, K. B. Low,, and K. E. Rudd,. 1996. Integrated linkage map of Escherichia coli K-12, edition 9, p. 1715 1902. In F. C. Neidhardt,, R. Curtiss III,, J. L. Ingraham,, E. C. C. Lin,, K. B. Low,, B. Magasanik,, W. Reznikoff,, M. Riley,, M. Schaechter,, and H. E. Umbarger (ed.), Escherichia coli and Salmonella; Cellular and Molecular Biology. 2nd ed. American Society for Microbiology, Washington, D.C..
6. Bhagwat, A. S.,, and M. McClelland. 1992. DNA mismatch correction by very short patch repair may have altered the abundance of oligonucleotides in the E. coli genome. Nucleic Acids Res. 20: 1663 1668.
7. Blakely, G.,, G. May,, R. McCulloch,, and L. K. Arciszewaska. 1993. Two related recombinases are required for chromosomal segregational cell division. New Biol. 8: 789 798.
8. Blattner, F. R.,, G. Plunkett III,, C. A. Bloch,, N. T. Perna,, V. Burland,, M. Riley,, J. Collado-Vides,, J. D. Glasner,, C. K. Rode,, G. F. Mayhew,, J. Gregor,, N. W. Davis,, H. A. Kirkpatrick,, M. A. Goeden,, D. J. Rose,, B. Mau,, and Y. Shao. 1997. The complete genome sequence of Escherichia coli K-12. Science 277: 1453 1462.
9. Bloch, C. A.,, and C. K. Rode. 1996. Pathogenicity island evaluation in Escherichia coli Kl by crossing with laboratory strain K-12. Infect. Immun. 64: 3218 3223.
10. Blomfield, I. C.,, M. S. McClain,, J. A. Princ,, P. J. Calie,, and B. A. Eisenstein. 1991. Type 1 fimbriation and ƒ im E mutants of Escherichia coli K-12. J. Bacteriol. 173: 5298 5307.
11. Blum, G.,, M. Ott,, A. Lischewski,, A. Ritter,, H. Imrich,, H. Tschape,, and J. Hacker. 1994. Excision of large DNA regions termed pathogenicity islands from tRNA-specific loci in the chromosome of an Escherichia coli wild-type pathogen. Infect. Immun. 62: 606 614.
12. Boyd, E. F.,, F. S. Wand,, P. Beltran,, S. A. Plock,, K. Nelson,, and R. K. Selander. 1993. Salmonella reference collection B (SARB): strains of 37 serovars of subspecies I. J. Gen. Microbiol. 139: 1125 1132.
13. Brewer, B. J. 1988. When polymerases collide: replication and the transcriptional organization of the E. coli chromosome. Cell 53: 679 686.
14. Burland, V.,, F. Plunkett III,, D. Daniels,, and F. R. Blattner. 1993. DNA sequence and analysis of 136 kilobases of Escherichia coli genome: organizational symmetry around the origin of replication. Genomics 16: 551 561.
15. Buvinger, W. E.,, K. A. Lampel,, R. J. Bojanowski,, and M. Riley. 1984. Location and analysis of nucleotide sequences at one end of a putative lac transposon in the Escherichia coli chromosome. J. Bacteriol. 159: 618 623.
16. Charlebois, R. L.,, and A. St. Jean. 1995. Supercoiling and map stability in the bacterial chromosome, J Mol. Evol. 41: 5 23.
17. Cornet, F.,, J. Louarn,, J. Patte,, and J.-M. Louarn. 1996. Restriction of the activity of the recombination site dif to a small zone of the Escherichia coli chromosome. Genes Dev. 10: 1152 1161.
18. Crosa, J. H.,, D. J. Brenner,, W. H. Ewing,, and S. Falkow. 1973. Molecular relationships among the Salmonellae . J. Bacteriol. 115: 307 315.
19. Dempsey, J. A.,, A. B. Wallace,, and J. G. Cannon. 1995. The physical map of the chromosome of a serogroup A strain of Neisseria meningitidis shows complex rearrangements relative to the chromosomes of the two mapped strains of the closely related species N. gonorrhoeae . J. Bacteriol. 177: 6390 6400.
20. Dybvig, K. 1993. DNA rearrangements and phenotypic switching in prokaryotes. Mol. Microbiol. 10: 465 471.
21. Fonstein, M.,, and R. Haselkorn. 1995. Physical mapping of bacterial genomes. J. Bacteriol. 177: 3361 3369.
22. Frankel, G.,, S. M. C. Newton,, G. K. Schoolnik,, and B. A. D. Stocker. 1989. In-tragenic recombination in a flagellin gene: characterization of the H1-j gene of Salmonella typhi . EMBO J. 8: 3149 3152.
23. Gibbs, C. P., and T. F. Meyers. 1996. Genome plasticity in Neisseria gonorrhoeae . FEMS Microbiol. Lett. 145: 173 179.
24. Groisman, E. A.,, and H. Ochman. 1996. Pathogenicity islands: bacterial evolution in quantum leaps. Cell 87: 791 794.
25. Haack, K.,, and J. Roth. 1995. Recombination between chromosomal IS 200 elements supports frequent duplication formation in Salmonella typhimurium . Genetics 141: 1231 1243.
26. Hessel, A.,, S.-L. Liu,, and K. E. Sanderson. 1995. The chromosome of Salmonella paratyphi C contains an inversion and is rearranged relative to S. typhimurium LT2, p. 503. In Abstracts of the 95th General Meeting of the American Society for Microbiology. 1995 . American Society for Microbiology, Washington, D.C..
27. Higgins, C. F.,, C. J. Dorman,, D. A. Stirling,, L. Waddell,, I. R. Booth,, G. May,, and E. Bremer. 1988. A physiological role for DNA supercoiling in the osmotic regulation of gene expression in S. typhimurium and E. coli . Cell 52: 569 584.
28. Hill, C. W.,, and J. A. Gray. 1988. Effects of chromosomal inversion on cell fitness in Escherichia coli K-12. Genetics 119: 771 778.
29. Hill, C. W.,, and B. W. Harnish. 1981. Inversions between ribosomal RNA genes of Escherichia coli . Proc. Natl. Acad. Sci. USA 78: 7069 7072.
29a.. Hill, T. M., 1996. Features of the chromosomal terminus region, p. 1602 1614. In F. C. Neidhardt,, R. Curtiss III,, J. L. Ingraham,, E. C. C. Lin,, K. B. Low,, B. Magasanik,, W. S. Reznikoff,, M. Riley,, M. Schaechter,, and H. E. Umbarger (ed.), Escherichia coli and Salmonella: Cellular and Molecular Biology, 2nd ed. American Society for Microbiology, Washington, D.C..
30. Honeycutt, B. W.,, M. McClelland,, and B. W. Sobral. 1993. Physical map of the genome of Rhizobium meliloti 1021. J. Bacteriol. 175: 6945 6952.
31. Kauffinan, F. 1966. The bacteriology of Enterobacteriaceae. Williams and Wilkens, Baltimore, Md..
32. Kim, S.-R.,, and T. Komano. 1992. Nucleotide sequence of the R721 shufflon. J. Bacteriol. 174: 7053 7058.
33. Kolsto, A.-B. 1997. Dynamic bacterial genome organization. Mol. Microbiol. 24: 241 248.
34. Krawiec, S.,, and M. Riley. 1990. Organization of the bacterial genome. Microbiol. Rev. 54: 502 539.
35. Krug, P. J.,, A. Z. Gileski,, R. J. Code,, A. Torjussen,, and M. B. Schmid. 1994. End-point bias in large Tn 10 -catalyzed inversions in Salmonella typhimurium . Genetics 136: 747 756.
36. Kuempel, P. L.,, J. M. Hensen,, L. Dircks,, M. Tecklenburg,, and D. F. Lim. 1991. dif a recA- independent recombination site in the terminus of the chromosome of Escherichia coli . New Biol. 3: 799 811.
37. Le Minor, L. 1988. Typing of Salmonella species. Eur.J. Clin. Microbiol. Infect. Dis. 7: 214 218.
38. Li, J.,, K. Nelson,, A. C. McWhorter,, T. S. Whittam,, and R. K. Selander. 1994. Recom-binational basis of serovar diversity in Salmonella enterica. Proc. Natl. Acad. Sci. USA 91: 2552 2556.
39. Liu, S.-L.,, A. Hessel,, H.-Y. M. Cheng,, and K. E. Sanderson. 1994. The XbaI- BlnI- CeuI genomic cleavage map of Salmonella paratyphi B. J. Bacteriol. 176: 1014 1024.
40. Liu, S.-L.,, A. Hessel,, and K. E. Sanderson. 1993. The Xba I -Bln I -Ceu I genomic cleavage map of Salmonella typhimurium LT2 determined by double digestion, end-labelling, and pulsed-field gel electrophoresis. J. Bacteriol. 175: 4104 4120.
41. Liu, S.-L.,, A. Hessel,, and K. E. Sanderson. 1993. Genomic mapping with I- Ceu I, an intron-encoded endonuclease, specific for genes for ribosomal RNA, in Salmonella spp., Escherichia coli, and other bacteria. Proc. Natl. Acad. Sci. USA 90: 6874 6878.
42. Liu, S.-L.,, A. Hessel,, and K. E. Sanderson. 1993. The Xba I -Bln I -Ceu I genomic cleavage map of Salmonella enteritidis shows an inversion relative to Salmonella typhimurium LT2. Mol. Microbiol. 10: 655 664.
43. Liu, S.-L.,, C. P.-F. Qi,, V. Stewart,, and K. E. Sanderson. 1997. A genome map of Klebsiella oxytoca M51a, p. 319. In Abstracts of the 97th General Meeting of the American Society for Microbiology 1997 . American Society for Microbiology, Washington, D.C..
44. Liu, S.-L.,, and K. E. Sanderson. 1992. A physical map of the Salmonella typhimurium LT2 genome made by using Xba I analysis. J. Bacteriol. 174: 1662 1672.
45. Liu, S.-L.,, and K. E. Sanderson. 1995. The chromosome of Salmonella paratyphi A is inverted by recombination between rrnH and rrnG . J. Bacteriol. 177: 6585 6592.
46. Liu, S.-L.,, and K. E. Sanderson. 1995. I -CeuI reveals conservation of the genome of independent strains of Salmonella typhimurium. J. Bacteriol. 177: 3355 3357.
47. Liu, S.-L.,, and K. E. Sanderson. 1995. The genomic cleavage map of Salmonella typhi Ty2. J. Bacteriol. 177: 5099 5107.
48. Liu, S.-L.,, and K. E. Sanderson. 1996. Highly plastic chromosomal organization in Salmonella typhi . Proc. Natl. Acad. Sci. USA 93: 10303 10308.
48a.. Liu, S.-L.,, and K. E. Sanderson. Unpublished data.
49. Louarn, J.,, F. Cornet,, V. Francois,, J. Patte,, and J.-M. Louarn. 1994. Hyperrecombination in the terminus region of the Escherichia coli chromosome: possible relation to nucleoid organization. J. Bacteriol. 176: 7524 7531.
50. Mahan, M. J.,, A. M. Segall,, and J. R. Roth,. 1990. Recombination events that rearrange the chromosome: barriers to inversion, p. 341 349. In K. Drlica, and M. Riley (ed.), The Bacterial Chromosome . American Society for Microbiology, Washington, D.C..
51. Marshall, P.,, T. B. Davis,, and C. Lemieux. 1994. The I- Ceul endonuclease: purification and potential role in the evolution of Chlamydomonas group I introns. Eur. J. Bacteriol 220: 855 859.
52. Marshall, P., and C. Lemieux. 1991. Cleavage pattern of the homing endonuclease encoded by the fifth intron in the chloroplast subunit rRNA-encoding gene of Chlamydomonas eugametos . Gene 104: 1241 1245.
53. McClelland, M.,, R. Jones,, Y. Patel,, and M. Nelson. 1987. Restriction endonucleases for pulsed field mapping of bacterial genomes. Nucleic Acids Res. 15: 5085 6005.
54. McDaniel, T. K.,, K. G. Jarvis,, M. S. Donnenberg,, and J. B. Kaper. 1995. A genetic locus of enterocyte effacement conserved among diverse enterobacterial pathogens. Proc. Natl. Acad. Sci. USA 92: 1664 1668.
55. Miller, W. G.,, and R. W. Simons. 1993. Chromosomal supercoiling in Escherichia coli . Mol. Microbiol. 10: 675 684.
56. Mills, D. M.,, V. Balaj,, and C. A. Lee. 1995. A 40 kilobase chromosomal fragment encoding Salmonella typhimurium invasion genes is absent from the corresponding region of the Escherichia coli chromosome. Mol. Microbiol. 15: 749 759.
57. Nelson, K.,, F.-S. Wang,, E. F. Boyd,, and R. K. Selander. 1997. Size and sequence polymorphism in the isocitrate dehydrogenase kinase/phosphatase gene ( aceK) and flanking regions in Salmonella enterica and Escherichia coli . Genetics 147: 1509 1520.
58. O'Brien, S. J.,, J. Wienberg,, and L. A. Lyons. 1997. Comparative genomics: lessons from cats. Trends Genet. 13: 393 398.
59. Ochman, H.,, F. C. Soncini,, F. Solomon,, and E. A. Groisman. 1996. Identification of a pathogenicity island required for Salmonella survival in host cells. Proc. Natl. Acad. Sci. USA 93: 7800 7804.
60. Ochman, H.,, and A. C. Wilson,. 1987. Evolutionary history of enteric bacteria, p. 1649 1654. In F. C. Neidhardt,, J. L. Ingraham,, K. B. Low,, B. Magasariik,, M. Schaechter,, and H. E. Umbarger (ed.), Escherichia coli and Salmonella typhimurium: Cellular and Molecular Biology . American Society for Microbiology, Washington, D.C..
61. Okada, N.,, C. Sasakawa,, T. Tobe,, K. A. Talukder,, K. Komatsu,, and M. Yoshikawa. 1991. Construction of a physical map of the chromosome of Shigella flexneri 2a and the direct assignment of nine virulence-associated loci identified by Tn5 insertions. Mol. Microbiol. 5: 2171 2180.
62. Pavitt, G. D.,, and C. F. Higgins. 1993. Chromosomal domains of supercoiling in Salmonella typhimurium . Mol. Microbiol. 10: 685 696.
63. PopofF, M. Y.,, J. Bockemuel,, and A. McWhorter-Murlin. 1993. Supplement 1992 (no. 36) to the Kaufrmann-White Scheme. Res. Microbiol. 144: 495 498.
64. Pruss, G. J.,, and K. Drlica. 1989. DNA supercoiling and prokaryotic transcription. Cell 56: 521 523.
65. Reeves, P. R. 1993. Evolution of O antigen variation by interspecific gene transfer on a large scale. Trends Genet. 9: 17 22.
66. Riley, M. L.,, and K. E. Sanderson,. 1990. Comparative genetics of Escherichia coli and Salmonella typhimurium, p. 85 95. In K. Drlica, and M. Riley (ed.), The Bacterial Chromosome . American Society for Microbiology, Washington, D.C..
67. Romero, D.,, and R. Palacios. 1997. Gene amplification and genomic plasticity in prokaryotes. Annu. Rev. Genet. 31: 91 111.
68. Roth, J. R.,, N. Benson,, T. Galitski,, K. Haack,, J. G. Lawrence,, and L. Miesel,. 1996. Rearrangements of the bacterial chromosome: formation and applications, p. 2256 2276. In F. C. Neidhardt,, R. Curtiss III,, J. L. Ingraham,, E. C. C. Lin,, K. B. Low,, B. Magasanik,, W. S. Reznikoff,, M. Riley,, M. Schaechter,, and H. E. Umbarger (ed.), Escherichia coli and Salmonella typhimurium; Cellular and Molecular Biology, 2nd ed. American Society for Microbiology, Washington, D.C..
69. Sanderson, K. E. 1976. Genetic relatedness in the family Enterobacteriaceae . Annu. Rev. Microbiol. 30: 327 349.
70. Sanderson, K. E.,, A. Hessel,, and K. E. Rudd. 1995. The genetic map of Salmonella typhimurium LT2, edition VIII. Microbiol. Rev. 59: 241 303.
71. Schmid, M.,, and J. R. Roth. 1987. Gene location affects expression level in Salmonella typhimurium . J. Bacteriol. 169: 2872 2875.
72. Selander, R. K.,, J. Li,, and K. Nelson,. 1996. Evolutionary genetics of Salmonella enterica, p. 2691 2707. In F. C. Neidhardt,, R. Curtiss III,, J. L. Ingraham,, E. C. C. Lin,, K. B. Low,, B. Magasanik,, W. S. Reznikoff,, M. Riley,, M. Schaechter,, and H. E. Umbarger (ed.), Escherichia coli and Salmonella: Cellular and Molecular Biology, 2nd ed. American Society for Microbiology, Washington, D.C..
73. Sharp, P. 1991. Determinants of DNA sequence divergence between Escherichia coli and Salmonella typhimurium: codon usage, map position, and concerted evolution. J. Mol Evol. 33: 23 33.
74. Silverman, M.,, and M. Simon. 1980. Phase variation: genetic analysis of switching mutants. Science 19: 845 854.
75. Sinden, R. R.,, and D. E. Pettijohn. 1981. Chromosomes in living Escherichia coli cells are segregated into domains of supercoiling. Proc. Natl. Acad. Sci. USA 78: 224 228.
76. Sirisena, D. M.,, P. R. MacLachlan,, S. L. Liu,, A. Hessel,, and K. E. Sanderson. 1994. Molecular analysis of the rfaD gene, for heptose synthesis, and the rfaF gene, for heptose transfer, in lipopolysaccharide synthesis in Salmonella typhimurium . J. Bacteriol. 176: 2379 2385.
77. Smith, C. L.,, J. Econome,, A. Schutt,, S. Klco,, and C. R. Cantor. 1987. A physical map of the Escherichia coli K-12 genome. Science 236: 1446 1453.
78. Smith, N. H.,, P. Beltran,, and R. K. Selander. 1992. Recombination of Salmonella phase-1 flagellin genes generates new serovars. J. Bacteriol. 172: 2209 2216.
78a.. Techlenburg, M.,, A. Maummer,, O. Nagap-pan,, and P. L. Kuempel. 1995. The dif- resolvase can be replaced by a 33 basepair sequence, but function depends on location. Proc. Natl. Acad. Sci. USA 92: 1352 1356.
79. Watanabe, H.,, H. Mori,, T. Itoh,, and T. Gojobori. 1997. Genome plasticity as a paradigm of eubacterial evolution. J Mol. Evol. 44( suppl.l): S57 S64.
80. Wong, K. K.,, and M. McClelland. 1992. A Blnl restriction map of the Salmonella typhimurium LT2 genome. J. Bacteriol. 174: 1656 1661.
81. Worcel, A.,, and E. Burgi. 1972. On the structure of the folded chromosome of Escherichia coli . J. Mol. Biol. 71: 127 147.
82. Xiang, S.-H.,, A. M. Haase,, and P. R. Reeves. 1993. Variation in the rfb gene clusters in Salmonella enterica . J. Bacteriol. 175: 4877 4884.
83. Zhang, X.-L.,, C. Morris,, and J. Hackett. 1997. Molecular cloning, nucleotide sequence, and function of a site-specific recombinase encoded in the major 'pathogenicity island' of Salmonella typhi . Gene 202: 139 146.

This is a required field
Please enter a valid email address
Please check the format of the address you have entered.
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error