Beneficial Microbes, December 2013; 4(4): 367-374 Wageningen Academic Publisher s ISSN 1876-2833 print, ISSN 1876-2891 online, DOI 10.3920/BM2013.0022 367 1. Introduction Probiotic bacteria often meet stressful conditions in the environments of their natural habitats such as high acidity and presence of bile salts during transit through the gastrointestinal tract (GIT). The ability to survive in these harsh environments is an important criterion during the selection of potential probiotics strains (Goh and Klaenhammer, 2009). Exposure of microbial cells to stress conditions involves a broad transcriptional response that includes the induction or repression of genes whose products are required to overcome the deleterious effects of stress (Serrazanetti et al., 2009; Van de Gutche et al., 2002). Bacteria have a complex network of stress response pathways to survive during environmental changes. As a result, a particular set of proteins including molecular chaperones and proteases can be expressed. Molecular chaperones assist in the correct folding of proteins and the proteases degrade the incorrectly folded ones (Suokko et al., 2005). Among chaperones and proteases, Clp proteins stand out. The Clp proteolytic complexes are widely conserved in Gram-positive bacteria and consist of a proteolytic core formed by 14 ClpP serine peptidases subunits, stacked in two heptameric rings, forming an internal channel flanked by Clp ATPases (Wang et al., 1997). These complexes play a vital role in the protein quality control system through refolding and/or degradation of damaged proteins (Frees et al., 2007). Lactobacillus delbrueckii UFV H2b20 is a strain able to survive under many stress conditions, such as acid and bile salts stress, and many studies have addressed its use as a probiotic strain carried out through dairy products Increased expression of clp genes in Lactobacillus delbrueckii UFV H2b20 exposed to acid stress and bile salts A.B. Ferreira 1 , M.N V. De Oliveira 2 , F.S. Freitas 1 , P. Alfenas-Zerbini 1 , D.F. Da Silva 3 , M.V. De Queiroz 1 , A.C. Borges 1 and C.A. De Moraes 1 1 Universidade Federal de Viçosa, Instituto de Biotecnologia Aplicada à Agropecuária-BIOAGRO, Departamento de Microbiologia, Viçosa, MG 36571-000, Brazil; 2 Universidade Federal de Juiz de Fora, Departamento Básico – Área de Saúde, Governador Valadares, MG 35020-220, Brazil; 3 Universidade Federal dos Vales do Jequitinhonha e Mucuri, Departamento de Nutrição, Diamantina, MG 39100-000, Brazil; alessandrabferreira@yahoo.com.br Received: 10 April 2013 / Accepted: 26 June 2013 © 2013 Wageningen Academic Publishers RESEARCH PAPER Abstract The ability to survive in harsh environments is an important criterion to select potential probiotics strains. The objective of this study was to identify and carry out phylogenetic and expression analysis by quantitative real-time PCR of the clpP, clpE, clpL and clpX genes in the probiotic strain Lactobacillus delbrueckii UFV H2b20 exposed to the conditions prevailing in the gastrointestinal tract (GIT). Phylogenetic trees reconstructed by Bayesian inference showed that the L. delbrueckii UFV H2b20 clpP, clpL and clpE genes and the ones from L. delbrueckii ATCC 11842 were grouped. The exposure of cells to MRS broth of pH 3.5 for 30 and 60 min resulted in an increased expression of the four genes. Exposure of the L. delbrueckii UFV H2b20 cells for 30 and 60 min to MRS broth containing 0.1% bile salts increased the expression of the clpP and clpE genes, while the expression level of the clpL and clpX genes increased only after 30 min of exposure. The involvement of the studied genes in the responses to acid stress and bile salts suggests a possible central role of these genes in the survival of L. delbrueckii UFV H2b20 during the passage through the GIT, a characteristic necessary for probiotic strains. Keywords: probiotics, stress response, molecular phylogeny, quantitative real-time PCR http://www.wageningenacademic.com/doi/pdf/10.3920/BM2013.0022 - Saturday, October 14, 2017 5:00:10 PM - Göteborgs Universitet IP Address:130.241.16.16