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The nucleotide sequence relatedness between the chromosome of Salmonella @phi and the virulence plasmid of Salmonella enteritidis was investigated using short DNA probes of < 2 kb covering the whole virulence plasmid Madrid, Spain sequence. Only one homologous region was detected. This region was subsequently cloned and partially sequenced. Sequences closely related to the pefl gene and the ORFs O d 7 , orf8 and om, which are located downstream of the f imbrial pef operon of the Salmonella typhimurium virulence plasmid, were detected. Sequencing of the cloned 5. @phi DNA fragment also revealed identity with genes of the fimbrial ref operon characterized in the chromosome of 5. enteritidis. These nucleotide sequences mapped upstream of the S. typhi chromosomal region homologous t o the 5. enteritidis virulence plasmid. The general organization of the cloned S. typhi chromosomal fragment was similar to the fimbriae-encoding region of the S. typhimurium virulence plasmid. The deduced product of od8 in the 5. typhimurium virulence plasmid, as well as those of the corresponding ORFs in the homologous region of the 5. typhi chromosome and in the 5. enteritidis virulence plasmid (designated dlt and dlp, respectively), appeared to be related to the thioredoxin family of thiol : disulphide oxidoreductases. The dlp gene was able to complement the DTT-sensitive phenotype, the inability to metabolize glucose I-phosphate and the low alkaline phosphatase activity of a dsbA mutant of Escherichia coli. The dlt gene partially complemented the lack of alkaline phosphatase activity, but not the other mutant phenotypes. The products of both genes could be detected using the T7 RNA polymerase promoter expression system. The estimated molecular masses of the products of the dlt and dlp genes by SDS-PAGE were 26 and 23 kDa, respectively, the first being in agreement with the deduced amino acid sequence and the latter, somewhat smaller. The processing of a possible leader peptide in the Dlp protein, but not in the Dlt protein, could be responsible for this difference. The Dlp protein appeared as a doublet band on SDS-PAGE, which is characteristic of the oxidized and reduced states of this kind of protein.Keywords : Salmonella typhi, Salmonella enteritidis, virulence plasmid, dsbA, dlt and dlPThe EMBL accession numbers for the sequences of dlt and dlp reported in this paper are X94325 and X94326, respectively.0002-1 197 0 1997 SGM

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Technology is among firms ownership advantages explaining their internationalisation as, now for decades, the eclectic approach has highlighted. The debate about the positive versus negative effects that foreign capital generates in the host economy has gained a new relevance today insofar as, on the one hand, the concept of systems of innovation allows us to rethink the interaction with the domestic/recipient economies and, on the other, the increasing internationalisation of the technological activities of multinational companies (MNCs) introduces new forms of that interaction. Therefore, the possibility of generation of external effects by MNCs today demands a new reformulation of the problem.In this vein, one of the strengthening aspects commonly underlined is that foreign knowledge, not completely appropriable by the foreign firms, may spill over into domestic firms. However, since the findings of the empirical evidence are not fully confirmatory of the hypothesis, and taking into account the new conditions, this essay attempts to offer new light with research about the Spanish manufacturing firms. Two main issues are focused on this analysis. First, the importance of dynamics in the assessment of technological spillovers motivated by foreign direct investment (FDI), which is possible thanks to the availability of a panel data for manufacturing firms in Spain in the period 1991-1999. Second, the importance that technology may have for the generation of spillovers and to what extent the Pavitt taxonomy of industries is still useful for in depth analysis of such a learning process.