Title page for ETD etd-05022007-150407

Type of Document Dissertation
Author Siddaramappa, Shivakumara Swamy
Author's Email Address ssiddara@vt.edu
URN etd-05022007-150407
Title Comparative and Functional Genomic Studies of Histophilus somni (Haemophilus somnus)
Degree PhD
Department Veterinary Medical Sciences
Advisory Committee
Advisor Name Title
Inzana, Thomas J. Committee Chair
Boyle, Stephen M. Committee Member
Meng, Xiang-Jin Committee Member
Mukhopadhyay, Biswarup Committee Member
Tyler, Brett M. Committee Member
  • Bacteriophage
  • Haemophilus
  • Genome
  • Histophilus
  • Plasmid
  • Restriction-Modification
  • LuxS
  • Biofilm
Date of Defense 2007-04-09
Availability unrestricted
Histophilus somni is a commensal of the mucosal surfaces of respiratory and reproductive tracts of cattle and sheep. However, as an opportunistic pathogen, H. somni can cause diseases such as pneumonia, myocarditis, abortion, arthritis, and meningo-encephalitis. Previously, several virulence factors/mechanisms had been identified in H. somni of which the phase-variable lipooligosaccharide, induction of host cell apoptosis, intraphagocytic survival, and immunoglobulin Fc binding proteins were well characterized. To further understand the biological properties of H. somni, the genomes of pneumonia strain 2336 and preputial strain 129Pt have been sequenced. Using the genome sequence data and comparative analyses with other members of the Pasteurellaceae, putative genes that encode proteases, restriction-modification enzymes, hemagglutinins, glycosyltransferases, kinases, helicases, and adhesins have been identified in H. somni. Most of the H. somni strain-specific genes were found to be associated with prophage-like sequences, plasmids, and/or transposons. Therefore, it is likely that these mobile genetic elements played a significant role in creating genomic diversity and phenotypic variability among strains of H. somni. Functional characterization of H. somni luxS in the genomic context revealed that the gene encodes S-ribosylhomocysteinase that can complement biosynthesis of AI-2 quorum sensing signal molecules in Escherichia coli DH5alpha. It was also found that several pathogenic isolates of H. somni form a prominent biofilm and that luxS as well as phosphorylcholine expression can influence biofilm formation by H. somni. In conclusion, comparative analyses of the genomes and functional characterization of putative genes have shed new light on the versatility and evolution of H. somni.
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  00_FRONT_MATTER.pdf 57.90 Kb 00:00:16 00:00:08 00:00:07 00:00:03 < 00:00:01
  01_CHAPTER_I.pdf 464.02 Kb 00:02:08 00:01:06 00:00:58 00:00:29 00:00:02
  02_CHAPTER_II.pdf 1.01 Mb 00:04:41 00:02:24 00:02:06 00:01:03 00:00:05
  03_CHAPTER_III.pdf 779.42 Kb 00:03:36 00:01:51 00:01:37 00:00:48 00:00:04
  04_CHAPTER_IV.pdf 1.45 Mb 00:06:43 00:03:27 00:03:01 00:01:30 00:00:07
  05_CHAPTER_V.pdf 449.39 Kb 00:02:04 00:01:04 00:00:56 00:00:28 00:00:02
  06_CHAPTER_VI.pdf 197.84 Kb 00:00:54 00:00:28 00:00:24 00:00:12 00:00:01

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