THE BIFIDOBACTERIA AND RELATED ORGANISMS: BIOLOGY, TAXONOMY, APPLICATIONS

This book is dedicated to Bifidobacterium, one of the bacterial genera most agreeable to humans and, as evidence increasingly suggests, most agreeable for the majority, if not all, mammals. What prompted the editors to submit the proposal for this new book was the awareness, supported by scientific evidence, of a growing interest in the role of beneficial microorganisms and, in particular, of bifidobacteria. This book presents authoritative reviews covering different aspects of bifidobacteria and other genera classified with them. Chapters 1, 2, and 3 introduce the reader to some fundamental aspects of taxonomy, underlining the current status of the phylum Actinobacteria, genus Bifidobacterium, and family Bifidobacteriaceae. Chapter 1 introduces the reader to the great differences between bifidobacteria and lactic acid bacteria. Although long assumed to be closely related, modern evidence shows that they are phylogenetically far removed and, in fact, members of completely different phyla. In recent years, the number of bifidobacterial species has greatly increased; currently 54 species and 10 subspecies are described. Lists of Bifidobacterium species and subspecies are available in Chapter 2. For each one a description and updated information from the literature are presented. Chapter 3 examines the family Bifidobacteriaceae. It highlights the characteristics of the seven new taxa belonging to the so-called scardovial genera, describing the features of genus and species. The chapter also includes a short remembrance of Professor Vittorio Scardovi, as recognition for the scientific importance of his work. Chapters 4–11 deal with physiological and biochemical aspects, providing essential information for a better understanding of bifidobacteria. Detailed advice is given for culture media and culture conditions for the detection of bifidobacteria in different environments, their cultivation, and their storage. Microbial chemistry is an important tool for identifying many major structural components and for understanding their functional role in the physiology of bacterial cells. Bifidobacteria are saccharolytic and derive their energy by fermentation, mainly from carbohydrates, such as lactose, the most abundant solid constituent of breast milk, or from “indigestible” oligosaccharides of plant origin. Multiple bifidobacterial species in the infant gut could be explained by specific human milk oligosaccharide consumption strategies. The number of published bifidobacterial genome sequences continues to grow, bringing a better understanding of the characteristic metabolic traits and key functions of the various species. Three chapters are devoted to the nutritional requirements of bifidobacteria, bifidogenic effect of particular substrates, milk oligosaccharides, and carbohydrate metabolism. Gut microbiota composition is an important health marker. Bifidobacteria are considered to be beneficial microorganisms. Studies on stress responses to oxygen and bile acid, the two major environmental stresses, provide information on their effects on growth and fermentation reactions of these anaerobes. Humans depend on externally supplied folate, and folate-producing bifidobacteria can be an important source of this vitamin for the host. A growing use of bifidobacteria for probiotics can also help alleviate the global nutritionally important health problem of folate deficiency. Exopolysaccharides are present on the surface of many bacteria, including Bifidobacterium. Their role in the colonization of their natural habitats and the cross-talk among bifidobacteria and host indicate their importance. Bifidobacteria are believed to have coevolved through beneficially influencing the health of their human host. Studies on their ecological distribution and genetic adaptation are essential to verify the hypotheses of coevolution. Genetic manipulation technologies in bifidobacteria and applications of currently available systems represent a topic with extraordinary growth potential in the near future. Administration of bifidobacteria in clinical trials for therapeutic purposes points out the variability linked to the strains used, which should stimulate the isolation of new strains with possibly new potential applications. Bifidobacteria are presently applied for therapeutic purposes in treating some pathogenic infections; at the same time, they are considered a hope for the future as an additional resource for human health. The immunological relevance of bifidobacteria shown by the immunomodulatory ability for the host is opening a new frontier for a rational modification of gut microbiota using specific bifidobacterial strains, to modify the immune responses not only in inflammatory or autoimmune disorders, but in other pathologies, such as cancer.A growing field is the use of bifidobacteria as health support in animal nutrition. One of the best examples currently available shows that these beneficial symbiotic bacteria (present in the honey stomach) possess antimicrobial characteristics and produce bioactive metabolites that protect honeybees against pathogens and also explain the therapeutically significant properties of honey. Production of probiotic bifidobacteria is more than just growing biomass. Many parameters affect their growth and stability, and the expression of their desired properties. These properties should therefore be considered early in the development of new probiotic strains. The term “probiotic” is raising a worldwide debate. A chapter with an overview of the definitions of the three terms: prebiotics, probiotics, and synbiotics, from both a scientific and a regulatory point of view, was therefore considered a necessary part of this book. As this preface reflects, the most important aspects of bifidobacteria were taken under consideration. The editors thank the publisher, who welcomed our proposal, as well as the authoritative international team of authors who made possible the realization of this book.