Improving the Digestive Tract Robustness of Probiotic Lactobacilli

This chapter describes stress responses of probiotic lactobacilli, in relation to gastrointestinal (GI-)tract robustness. An overview is given of some newly developed tools to understand and improve stress responses of the model probiotic L. plantarum WCFS1 in relation to its GI persistence. These include a relative simple GI-tract assay and the development of transcriptome-trait matching that associates a trait of interest (e.g., GI-tract survival) with transcripts levels that enables the identification of genetic robustness markers, that can be modulated by pre-adaptation and/or genetic engineering to enhance robustness. Furthermore, specific additives to the in situ delivery matrix may enhance the relative tolerance of specific bacterial strains to detrimental conditions they may encounter in different regions of the GI-tract. Moreover, a methodology that allows the molecular quantification of single strains in a mixed bacterial population using engineered sequence-tags or naturally occurring discriminatory intergenic alleles in combination with next-generation sequencing offers another powerful tool for robustness evaluation. Finally, the stress responses of probiotic cultures in relation to improval of their GI persistence and some future directions for development and GI-tract research in the light of probiotic performance are discussed.