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Infection and Immunity, June 2008, p. 2411-2419, Vol. 76, No. 6
0019-9567/08/$08.00+0 doi:10.1128/IAI.01730-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Identification of a Novel Prophage-Like Gene Cluster Actively Expressed in Both Virulent and Avirulent Strains of Leptospira interrogans Serovar Lai 
Jin-Hong Qin,1,
Qing Zhang,2,
Zhi-Ming Zhang,3
Yi Zhong,1
Yang Yang,1
Bao-Yu Hu,1
Guo-Ping Zhao,2,3* and
Xiao-Kui Guo1*
Department of Microbiology and Parasitology, Institutes of Medical Sciences, Shanghai Jiao Tong University, School of Medicine, Shanghai 200025, China,1 Laboratory of Molecular Microbiology, Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China,2 Shanghai-MOST Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai and National Engineering Center for BioChip at Shanghai, Shanghai 201203, China3
Received 23 December 2007/ Returned for modification 7 January 2008/ Accepted 13 March 2008
DNA microarray analysis was used to compare the differential gene expression profiles between Leptospira interrogans serovar Lai type strain 56601 and its corresponding attenuated strain IPAV. A 22-kb genomic island covering a cluster of 34 genes (i.e., genes LA0186 to LA0219) was actively expressed in both strains but concomitantly upregulated in strain 56601 in contrast to that of IPAV. Reverse transcription-PCR assays proved that the gene cluster comprised five transcripts. Gene annotation of this cluster revealed characteristics of a putative prophage-like remnant with at least 8 of 34 sequences encoding prophage-like proteins, of which the LA0195 protein is probably a putative prophage CI-like regulator. The transcription initiation activities of putative promoter-regulatory sequences of transcripts I, II, and III, all proximal to the LA0195 gene, were further analyzed in the Escherichia coli promoter probe vector pKK232-8 by assaying the reporter chloramphenicol acetyltransferase (CAT) activities. The strong promoter activities of both transcripts I and II indicated by the E. coli CAT assay were well correlated with the in vitro sequence-specific binding of the recombinant LA0195 protein to the corresponding promoter probes detected by the electrophoresis mobility shift assay. On the other hand, the promoter activity of transcript III was very low in E. coli and failed to show active binding to the LA0195 protein in vitro. These results suggested that the LA0195 protein is likely involved in the transcription of transcripts I and II. However, the identical complete DNA sequences of this prophage remnant from these two strains strongly suggests that possible regulatory factors or signal transduction systems residing outside of this region within the genome may be responsible for the differential expression profiling in these two strains.
* Corresponding author. Mailing address for G.-P. Zhao: Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China. Phone: 86-21-54924002. Fax: 86-21-50801922. E-mail: gpzhao{at}sibs.ac.cn. Mailing address for X.-K. Guo: Department of Microbiology and Parasitology, Shanghai Jiao Tong University, School of Medicine, Shanghai 200025, China. Phone and fax: (86) 21-64453285. E-mail: microbiology{at}sjtu.edu.cn
Published ahead of print on 24 March 2008.
J.-H.Q. and Q.Z. contributed equally to this study.
Infection and Immunity, June 2008, p. 2411-2419, Vol. 76, No. 6
0019-9567/08/$08.00+0 doi:10.1128/IAI.01730-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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