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Applied and Environmental Microbiology, July 2003, p. 4219-4226, Vol. 69, No. 7
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.7.4219-4226.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Department of Microbiology,1 National Food Biotechnology Centre,2 Department of Food Science, Food Technology and Nutrition, National University of Ireland, Cork, Ireland3
Received 30 December 2002/ Accepted 23 April 2003
Two-component signal transduction systems (2CSs) are widely used by bacteria to sense and adapt to changing environmental conditions. With two separate approaches, three different 2CSs were identified on the chromosome of the probiotic bacterium Bifidobacterium infantis UCC 35624. One locus was identified by means of functional complementation of an Escherichia coli mutant. Another two were identified by PCR with degenerate primers corresponding to conserved regions of one protein component of the 2CS. The complete coding regions for each gene cluster were obtained, which showed that each 2CS-encoding locus specified a histidine protein kinase and an assumed cognate response regulator. Transcriptional analysis of the 2CSs by Northern blotting and primer extension identified a number of putative promoter sequences for this organism while revealing that the expression of each 2CS was growth phase dependent. Analysis of the genetic elements involved revealed significant homology with several distinct regulatory families from other high-G+C-content bacteria. The conservation of the genetic organization of these three 2CSs in other bacteria, including a number of recently published Bifidobacterium genomes, was investigated.
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