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Factors involved with PAPI-1 mobilization

Grant number: 07/02328-2
Support Opportunities:Scholarships in Brazil - Master
Effective date (Start): March 01, 2008
Effective date (End): August 31, 2009
Field of knowledge:Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
Principal Investigator:Regina Lúcia Baldini
Grantee:Eliezer Stefanello
Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil


Although the large amount of data generated by the sequenced genomes of various organisms is available, the information is not enough for the understanding of cellular processes. Bacterial genes may be transferred among different organisms via conjugation, transduction and transformation. Most of the regions acquired by horizontal DNA transfer is part of the flexible pool of genes, which includes plasmids, phages, transposons, integrons and genomic islands. Genomic islands are located in the bacterial chromosomes and may provide the organism a selective advantage and are present only in some strains of a given species. Among these regions are the pathogenicity islands containing virulence-related genes. PAPI-1 is a pathogenicity island of the opportunistic pathogen Pseudomonas aeruginosa PA14 that comprises 115 open reading frames (RL001-RL115), presents a lower G+C content (59,7%) than the average of the chromosome (66,3%) and it is localized next to a tRNALys gene, being also detected in circular form at low frequencies. Several PAPI-1 gene clusters are homologous to genes present in the plasmids pKLC102 e pKLK106 and in genomic islands in about thirty P. aeruginosa strains. These blocks of conserved genes are not exclusive to P. aeruginosa and can be found in several beta- and gamma-proteobacteria in regions of the genome with characteristics of horizontally acquired regions. Mohd-Zain et al. (J. Bacteriol., 186: 8114, 2004) defined a core of 33 genes which characterize a family of related genomic islands, all present in PAPI-1. This family of genomic islands includes a region of 86 kb that comprises 82 ORFs of the phytopathogen Xanthomonas campestris pv. citri 306 (XAC), the causative agent of citrus canker. This putative XAC genomic island presents a G+C content of 69,6%, while the genome average is 64%. This region contains the ORFs annotated as XAC2205 a XAC2286 and twenty-eight of them are homologous to the core genes defined by Mohd-Zain. Part of this island is represented by the XAC-specific "unusual best-match island" A4, with ORFs XAC2237 to XAC2268. The islands of this family present in PA14 and XAC shares thirty-two genes, and, besides four involved in replication and recombination, no functions can be inferred from sequence comparison with know genes. The genes dispersed between the conserved regions in the two bacteria present different roles: whereas genes related to adhesion are found in PAPI-1, XAC genes codify enzymes such as NAD(P)H dehydrogenase and glutathione-S-transferase. With the aim to understand the function of the genes conserved in the genomic islands of PA14 and XAC, this proposal intends to analyze whether the protein coded by them interact and whether those gene products are responsible for the excision of the islands from the chromosome. If the proteins analyzed interact with others coded in the same island, it could be inferred that they participate in a same pathway or process, their genes being conserved as blocks during evolution. Furthermore, if this approach discloses interaction with proteins coded elsewhere in the chromosome, it would point to a broader role of the genes acquired by horizontal transfer as they could interfere with processes which players are not coded in the islands. (AU)

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Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
STEFANELLO, Eliezer. Factors involved with PAPI-1 mobilization. 2010. Master's Dissertation - Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) São Paulo.

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