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Category: Food Microbiology
Probiotics and Prebiotics, Page 1 of 2
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Probiotics, live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, and prebiotics, substrates that are selectively utilized by host microorganisms conferring a health benefit, make up a group of highly researched substances targeted at influencing microbiota-mediated functions for the benefit of the host. Evidence that probiotics and prebiotics can benefit human and animal health continues to build and fuel basic research on mechanisms, genomics, and genetic improvement of these substances. This chapter explores basic mechanisms of probiotic and prebiotic function, next-generation probiotics and prebiotics, comparative genomics, taxonomy and molecular identification, health benefits for humans and animals, and safety and regulatory issues.
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Elie Metchnikoff (1845–1916) ( 125 ).
Probiotics: what is encompassed under this term. By definition, a health benefit must be demonstrated for a probiotic, either at a strain-specific level or at a taxonomic level where mechanisms are shared. Probiotics can be administered via different routes (oral, intravaginal, and topical routes and via mouth sprays) and are not limited to human use (i.e., they may also be given to companion animals, livestock, and fish). The probiotic definition is not restricted by regulatory category for probiotics and encompasses the spectrum from foods to drugs (live biotherapeutic agents). Dead microbes, microbial end products, microbial components, and undefined microbial mixes do not come under the probiotic classification. Adapted from reference 34 with permission.
Genome atlas of the probiotic L. acidophilus strain NCFM, presenting a circular view of the complete genome. The key describes the single circles in the top-down outermost-innermost direction ( 126 ).
Overview of indications where probiotics have been researched with varying but solid evidence for clinical benefit. RTI, respiratory tract infection; GI, gastrointestinal.
Comparison of the complete genome sequences of B. animalis subsp. lactis DSM 10140 and Bl-04, showing a hierarchical clustering analysis of B. animalis subsp. lactis strains across 50 genetic loci. Rows represent strains, and columns represent genetic loci. Numbers on the right indicate strain clusters, and numbers on the bottom indicate genetic locus clusters. Colored squares correspond to the sequence type at each locus. Blue represents strain DSMZ 10140, red represents strain Bl-04, and gray represents unique sequence ( 74 , 127 ).
Bacteriocin production by L. salivarius UCC118 protects against L. monocytogenes EGDe infection of mice. (Top left) Bacteriocin production by wild-type (wt) UCC118 and the non-bacteriocin-producing mutant. (Bottom left) Bars represent mice fed placebo (black), UCC118 (white), or a non-bacteriocin-producing mutant of UCC118 (gray). (Right) Image on the cover of Proceedings of the National Academy of Sciences shows livers of mice that are colonized with luminescent L. monocytogenes EGDe, in red. Adapted from reference 35 with permission.
Pili expressed by L. rhamnosus (left) ( 85 ) and B. breve (right) ( 86 ).
Examples of prebiotic oligosaccharides with demonstrated health effects through modulation of beneficial microbiota. FFn, FOS generated from partial hydrolysis of inulin; GFn, FOS synthesized from sucrose; LNB, lacto-N-biose I; LNT, lacto-N-tetraose. The structure of HMO is modified from reference 121 ; figure modified from reference 107 .
Metabolism of prebiotic compounds by beneficial gut microbiota and probiotic microorganisms, by which the resulting population is enhanced directly and indirectly (via substrate cross-feeding and metabolic cross-feeding) and which has health-promoting effects on the host. SCFAs are an essential energy source for colonic epithelial cells and serve as growth factors for some beneficial bacteria. These metabolites have also been associated with maintenance of gut barrier integrity, immunomodulatory functions, and host signaling ( 39 , 100 ). Dashed arrows indicate cross-feeding of hydrolyzed prebiotic substrate intermediates and SCFA metabolites.
Molecular mechanisms of prebiotic FOS and GOS uptake and catabolism identified among intestine-associated lactobacilli. A diverse array of transport systems (ABC transporter, sucrose and fructose PTSs, symporter) and hydrolytic pathways (intracellular versus extracellular) have evolved for FOS utilization in these organisms (top). Uptake of GOS is mainly mediated by lactose permeases and is hydrolyzed by cytoplasmic β-galactosidases (bottom). Note that no LacS permease ortholog was identified in the L. casei-L. paracasei group. FFase, β-fructofuranosidase or β-fructosidase; ~P, phosphorylation of the substrate intermediate during the uptake process via PTS; an asterisk indicates that the transporter system was predicted based on in silico analysis.
Terminology related to probiotics a
Mechanisms of action that may mediate health benefits conferred by specific probiotic strains
Examples of probiotic strains with research documentation in human subjects a
Characteristics important for probiotic strains