Abstract
PhoP/PhoQ two-component regulatory system which controls virulence and intramacrophage survival of Salmonella typhimurium has been detected in several other species. Salmonella phoP::TnlO mutants are highly sensitive to serum, defensin and acid. In this study, a phop-like gene designated as tcrp was isolated from B. abortus. Following the initial amplification of a 300 base pair phop-like gene fragment using PCR degerate primers based on homologous amino acid sequences shared by S. typhimurium phop and E. coli phob, a larger DNA fragment (3355 bp) was isolated from B. abortus k Zapll genomic library, which contained the intact tcrp gene and its upstream and downstream sequences. The deduced amino acid sequence of tcrp exhibited 41% homology to S. typhimurium PhoP and also showed general features of the members of two-component regulatory proteins. A B. abortus strain carrying tcrp mutation was constructed for testing the putative functions of the tcrp gene. The results from these test showed that the tcrp mutants exhibited increased (10 fold) sensitivity to complement mediated lysis, which was not due to 0-antigen defect. The tcrp mutant also showed a slightly increased acid sensitivity (1.5 fold). No significant differences were found between the tcrp mutants and wild type strains in peptide sensitivity and hydrogen peroxide killing tests. Based on the preliminary phenotypic tests, the putative functions of tcrp gene and the experiments for further characterization of this gene were discussed.
Huang, Xin (1997). Isolation and characterization of PhoP homolog in Brucella abortus. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -H83.