| Área: Microbiologia de Alimentos ( Divisão K ) PRESENCE OF LACTOBACILLUS SAKEI AND BACTERIOCIN GENE EXPRESSION IN SAMPLES TAKEN FROM HUMAN GASTROINTESTINAL TRACT Martha Lissete Villarreal Morales (WUR); Bernadette Dora Gombossy de Melo Franco (FCF-USP); Susana Marta Isay Saad (FCF-USP); Erwin G Zoetendal (WUR)
Resumo
Lactobacillus sakei is commonly associated with fermented foods, both animal and vegetable. This species has also been shown to be a transient member of the human gastrointestinal microbiota. As many other lactic acid bacteria, certain L. sakei strains produce antimicrobial substances such as bacteriocins, which play a crucial role in meat preservation and fermentation towards pathogenic or spoilage bacteria. It has been suggested that the production of bacteriocins by probiotic strains might contribute for the resistance of humans to gastrointestinal colonization by pathogens. However, our knowledge about in vivo bacteriocin gene expression in the gastrointestinal tract (GIT) is limited. This work aimed to link the presence of L. sakei to the production of bacteriocins in the GIT. A qualitative and quantitative analysis of the bacterial community in fecal samples from 14 healthy volunteers was carried out using 16S rRNA and sakacin gene-specific qPCR, focusing on the lactobacilli community and on L. sakei. L. sakei was detected in 9 of 14 individuals sampled (64.3%), regardless of their diet, pointing out that it can persist in the colon as a normal inhabitant of the GIT. L. sakei was present at 105 and 106 gene copy/g of feces, representing between 0.1 to 11.4% of total lactobacilli community in the positive samples. Strain L. sakei 2a, isolated at São Paulo University and well known as bacteriocin producer against Listeria monocytogenes and Staphylococcus aureus, was used as a model strain to develop a Reverse Transcription-quantitative PCR (RT-qPCR) method to monitor sakacin gene expression. Monitoring L. sakei 2a gene expression in vitro revealed the concomitant production of two sakacins by L. sakei 2a: sakacin P and sakacin Q. The genes that encode for both bacteriocins were especially expressed during the exponential growth phase in MRS medium. The sakacin P and Q expression in situ in the GIT were just below the detection limit of the RT-qPCR assay. Whether this was due to the low numbers of L. sakei, its growth phase in feces or other factors remains to be determined in the near future.
Financial support: CAPES, WUR
Key words: Lactobacillus sakei, bacteriocins, Reverse Transcription-quantitative PCR, gene expression
Palavras-chave: Bacteriocins, Gene expression, Human gastrointestinal microbiota, Lactobacillus sakei, Reverse Transcription-quantitative PCR |