Abstract
The analysis of collections of lactic acid bacteria (LAB) from traditional fermented plant foods in tropical countries may enable the detection of LAB with interesting properties. Binding capacity is often the main criterion used to investigate the probiotic characteristics of bacteria. In this study, we focused on a collection of 163 Lactobacillaceace comprising 156 bacteria isolated from traditional amylaceous fermented foods and seven strains taken from a collection and used as controls. The collection had a series of analyses to assess binding potential for the selection of new probiotic candidates. The presence/absence of 14 genes involved in binding to the gastrointestinal tract was assessed. This enabled the detection of all the housekeeping genes (ef-Tu, eno, gap, groEl and srtA) in the entire collection, of some of the other genes (apf, cnb, fpbA, mapA, mub) in 86% to 100% of LAB, and of the other genes (cbsA, gtf, msa, slpA) in 0% to 8% of LAB. Most of the bacteria isolated from traditional fermented foods exhibited a genetic profile favorable for their binding to the gastrointestinal tract. We selected 30 strains with different genetic profiles to test their binding ability to non-mucus (HT29) and mucus secreting (HT29-MTX) cell lines as well as their ability to degrade mucus. Assays on both lines revealed high variability in binding properties among the LAB, depending on the cell model used. Finally, we investigated if their binding ability was linked to tighter cross-talk between bacteria and eukaryotic cells by measuring the expression of bacterial genes and of the eukaryotic MUC2 gene. Results showed that wild LAB from tropical amylaceous fermented food had a much higher binding capacity than the two LAB currently known to be probiotics. However their adhesion was not linked to any particular genetic equipment.
Highlights
Lactic acid bacteria (LAB) are common inhabitants of a wide variety of environments including the mucosal surfaces of humans and animals and food environments made of milk, plants, and meats
One possible link between bacterial binding ability and genetic equipment was investigated in each LAB strain by comparing their corresponding gene set determined by PCR with their ability to adhere to enterocyte-like cells (HT29), and mucus secreting cells (HT29-MTX)
Genetic screening was used as it is expected to enable more rapid identification of any LAB potentially able to bind to the digestive tract than cell culture, which is more time consuming when used for a large set of bacterial isolates
Summary
Lactic acid bacteria (LAB) are common inhabitants of a wide variety of environments including the mucosal surfaces of humans and animals and food environments made of milk, plants, and meats. Supplementary data are needed on immunomodulation, resistance to acid and bile, production of bacteriocins, and adhesion to the intestinal tract [4,5] to establish a link between consumption of fermented foods and health benefits. The binding of probiotic bacteria to intestinal cells is expected to have lasting beneficial effects for health including the exclusion of pathogens, immunomodulation and the production of beneficial bacterial molecules [6]. The increasing amount of data dealing with the molecular origin of adhesion has improved our understanding of binding mechanisms. Proteins involved in this mechanism can be separated into five classes: anchorless housekeeping proteins, surface layer proteins, LPXTG-motif proteins, transporter proteins and ‘other’ proteins [7]. We performed a series of analyses of a collection of 162 LAB strains to assess their binding potential as part of the selection of new probiotic candidates
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