Molecular Studies of Restriction Genes in Enteric Bacteria

<p>Bacterial cells contain various restriction-modification (R-M) systems to protect themselves from incoming foreign DNA. Most bacteria have at least one such system. In this study, the restriction genes and the location of the genes on the chromosome were examined in three enteric bacteria. <em>Salmonella typhimurium</em> LT2, <em>Klebsiella pneumoniae</em> GM 236, and <em>Klebsiella pneumoniae</em> M5al. The 98 minute region of the <em>Salmonella typhimurium</em> LT2 chromosome comprises at least two R-M systems. From genetic data this region was previously thought to be only one minute in length but was found to be larger than two minutes using a physical mapping technique, pulsed field gel electrophoresis (PFGE).</p> <p>The KpnAI and KpnBI R-M systems were recognized in <em>K. pneumoniae</em> strain M5al and GM236, respectively. A macro-restriction map of <em>Klebsiella pneumoniae</em> GM236 was constructed in this study using PFGE and Southern hybridization. The genome was digested with three rare cutting restriction enzymes (<em>BlnI, I-Cuel</em> and <em>XBal</em>). The estimated size of the GM236 genome was 4,582 (±80) kb, in accordance with the range of other enteric bacteria. The partial digest of <em>I-Cuel </em>allowed a tentative ordering of the eight fragments on a circular map. The map was remarkably similar to the map of <em>Escherichia coli</em> and <em>S. typhimurium</em> with the exception of two fragments. <em>I-Cuel</em> cuts the GM236 chromosome in eight fragments whereas it cuts E. coli and Salmonella genomes This suggests a possible in seven. duplication of the ribosomal cluster in the GM236 strain. The constructed map, although tentative, has permitted the mapping of hsdR KpnBI’ a restriction gene located on a 322 ^kpmBI+ fragment and also on a 40 kb <em>Xbal</em> fragment.</p> <p>In this study,<em> hsdR_KpnA1</em>, another restriction gene recognized in <em>K. pneumoniae</em> M5al, was subcloned and sequenced. The DNA sequence of 4.5 kb was determined and only one open reading frame (ORF) of 3, 305 base pair (bp) was considered as the coding region for the HsdR_KpnAI polypeptide. The nucleotide sequence of the HsdR_KpnA gene showed no significant similarity to any other sequences in the GenBank database. However, the deduced amino acid sequence showed a moderate degree of homology (26%) with <em>Eco</em>R\2AH (former £cK. pneumoniae.</em></p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Year

1996

Author dc:creator

• Rutebuka, Obed B.

Contributors dc:contributor

• Junichi Ryu
• Leonard Brand
• Ronald L. Carter
• David L. Cowels
• E. Clifford Herrmann

• Biology
• Bacteria; Genome, Bacterial; DNA, Bacterial; DNA Restriction Enzymes; Salmonella typhimurium; Klebsiella pneumoniae; Escherichia coli; Bacteriophages

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/757

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1866