Publicação
The Tat pathway in Listeria monocytogenes
| Resumo: | Listeria monocytogenes, a foodborne pathogenic bacterium, remains a serious public health concern due to its frequent occurrence in food products coupled with a high mortality rate, specially among immunocompromised hosts. Bacterial pathogenicity depends greatly on the ability to secrete virulence factors to or beyond the bacterial cell surface. Thus, the study of secreted proteins is of crucial importance to further develop defensive strategies. The Tat pathway, one of the secretion systems present in L. monocytogenes, was until now only investigated in silico. Therefore, a better understanding of the Tat pathway was needed. In L. monocytogenes, strain EGDe, two proteins constitute the Tat pathway and are encoded in the genes tatC (lmo0361) and tatA (lmo0362). In the present study, a L. monocytogenes mutant strain lacking the genes coding for the Tat pathway was successfully constructed (EGDe ΔtatAC). The mutant showed the ability to grow at the same growth rate as the parent strain, proving that the Tat pathway is not essential for L. monocytogenes survival. Moreover this study showed that both genes are transcribed in a bicistronic and growth-phase dependent manner. The deletion mutant for the Tat pathway showed no differences in the in vitro virulence potential, but significant differences (p < 0.05) were found when in vivo virulence potential was assessed, being the tat mutant more virulent than the wild-type strain. Regulation of tatAC was also investigated, and a deletion mutant for lmo0364, a gene coding for a transcription regulator, localized close to the tat genes, was constructed. Our results show that Lmo0364 is not related to the other genes in the locus, as it is not involved in the transcription regulation of any of the genes analyzed. This is, to our knowledge, the first experimental study on the Tat pathway of L. monocytogenes. Here we show that this pathway is not essential for the bacterium and that it might be impairing its virulence ability. |
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| Autores principais: | Machado, Henrique Ramalho, 1988- |
| Assunto: | Microbiologia Bactérias patogénicas Secreção Mutante Listeria monocytogenes Teses de mestrado - 2011 |
| Ano: | 2011 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Listeria monocytogenes, a foodborne pathogenic bacterium, remains a serious public health concern due to its frequent occurrence in food products coupled with a high mortality rate, specially among immunocompromised hosts. Bacterial pathogenicity depends greatly on the ability to secrete virulence factors to or beyond the bacterial cell surface. Thus, the study of secreted proteins is of crucial importance to further develop defensive strategies. The Tat pathway, one of the secretion systems present in L. monocytogenes, was until now only investigated in silico. Therefore, a better understanding of the Tat pathway was needed. In L. monocytogenes, strain EGDe, two proteins constitute the Tat pathway and are encoded in the genes tatC (lmo0361) and tatA (lmo0362). In the present study, a L. monocytogenes mutant strain lacking the genes coding for the Tat pathway was successfully constructed (EGDe ΔtatAC). The mutant showed the ability to grow at the same growth rate as the parent strain, proving that the Tat pathway is not essential for L. monocytogenes survival. Moreover this study showed that both genes are transcribed in a bicistronic and growth-phase dependent manner. The deletion mutant for the Tat pathway showed no differences in the in vitro virulence potential, but significant differences (p < 0.05) were found when in vivo virulence potential was assessed, being the tat mutant more virulent than the wild-type strain. Regulation of tatAC was also investigated, and a deletion mutant for lmo0364, a gene coding for a transcription regulator, localized close to the tat genes, was constructed. Our results show that Lmo0364 is not related to the other genes in the locus, as it is not involved in the transcription regulation of any of the genes analyzed. This is, to our knowledge, the first experimental study on the Tat pathway of L. monocytogenes. Here we show that this pathway is not essential for the bacterium and that it might be impairing its virulence ability. |
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