The human gastrointestinal tract is colonised by a complex ecosystem of microorganisms. Intestinal bacteria are not only commensal, but they also undergo a synbiotic co-evolution along with their host. Beneficial intestinal bacteria have numerous and important functions, e.g., they produce various nutrients for their host, prevent infections caused by intestinal pathogens, and modulate a normal immunological response. Therefore, modification of the intestinal microbiota in order to achieve, restore, and maintain favourable balance in the ecosystem, and the activity of microorganisms present in the gastrointestinal tract is necessary for the improved health condition of the host. The introduction of probiotics, prebiotics, or synbiotics into human diet is favourable for the intestinal microbiota. They may be consumed in the form of raw vegetables and fruit, fermented pickles, or dairy products. Another source may be pharmaceutical formulas and functional food. This paper provides a review of available information and summarises the current knowledge on the effects of probiotics, prebiotics, and synbiotics on human health. The mechanism of beneficial action of those substances is discussed, and verified study results proving their efficacy in human nutrition are presented.

https://www.mdpi.com/2072-6643/9/9/1021/pdf

Effects of Probiotics, Prebiotics, and Synbiotics on Human Health.

Probiotic bacteria: safety, functional and technological properties

Summary: Actinobacteria constitute one of the largest phyla among Bacteria and represent gram-positive bacteria with a high G+C content in their DNA. This bacterial group includes microorganisms exhibiting a wide spectrum of morphologies, from coccoid to fragmenting hyphal forms, as well as possessing highly variable physiological and metabolic properties. Furthermore, Actinobacteria members have adopted different lifestyles, and can be pathogens (e.g., Corynebacterium, Mycobacterium, Nocardia, Tropheryma, and Propionibacterium), soil inhabitants (Streptomyces), plant commensals (Leifsonia), or gastrointestinal commensals (Bifidobacterium). The divergence of Actinobacteria from other bacteria is ancient, making it impossible to identify the phylogenetically closest bacterial group to Actinobacteria. Genome sequence analysis has revolutionized every aspect of bacterial biology by enhancing the understanding of the genetics, physiology, and evolutionary development of bacteria. Various actinobacterial genomes have been sequenced, revealing a wide genomic heterogeneity probably as a reflection of their biodiversity. This review provides an account of the recent explosion of actinobacterial genomics data and an attempt to place this in a biological and evolutionary context.

Genomics of Actinobacteria: Tracing the Evolutionary History of an Ancient Phylum

Food products fermented by lactic acid bacteria have long been used for their proposed health promoting properties. In recent years, selected probiotic strains have been thoroughly investigated for specific health effects. Properties like relief of lactose intolerance symptoms and shortening of rotavirus diarrhoea are now widely accepted for selected probiotics. Some areas, such as the treatment and prevention of atopy hold great promise. However, many proposed health effects still need additional investigation. In particular the potential benefits for the healthy consumer, the main market for probiotic products, requires more attention. Also, the potential use of probiotics outside the gastrointestinal tract deserves to be explored further. Results from well conducted clinical studies will expand and increase the acceptance of probiotics for the treatment and prevention of selected diseases.

Probiotics: an overview of beneficial effects

Probiotic functional foods: Survival of probiotics during processing and storage

The species Bifidobacterium lactis, with its main representative strain Bb12 (DSM 10140), is a yoghurt isolate used as a probiotic strain and is commercially applied in different types of yoghurts and infant formulas In order to ensure the genetic identity and safety of this bacterial isolate, species- and strain-specific molecular tools for genetic fingerprinting must be available to identify isolated bifidobacteria or lactic acid bacteria from, eg, various clinical environments of relevance in medical microbiology Two opposing rRNA gene-targeted primers have been developed for specific detection of this microorganism by PCR The specificity of this approach was evaluated and verified with DNA samples isolated from single and mixed cultures of bifidobacteria and lactobacilli (48 isolates, including the type strains of 29 Bifidobacterium and 9 Lactobacillus species) Furthermore, we performed a Multiplex-PCR using oligonucleotide primers targeting a specific region of the 16S rRNA gene for the genus Bifidobacterium and a conserved eubacterial 16S rDNA sequence The specificity and sensitivity of this detection with a pure culture of B lactis were, respectively, 100 bacteria/ml after 25 cycles of PCR and 1 to 10 bacteria/ml after a 50-cycle nested-PCR approach

Specific identification and targeted characterization of Bifidobacterium lactis from different environmental isolates by a combined multiplex-PCR approach.

One important task of the Fair CT96-1028 project (Demonstration of Nutritional Functionality of Probiotic Foods) has been to demonstrate the possibility of producing, on a pilot scale, probiotic dairy foods acceptable to European consumers. In the project, different Lactobacillus spp. and Bifidobacterium spp. strains were shown to be suitable for probiotic organisms. Culture concentrates were produced by standard methods, and showed high cell concentrations and good survival during storage at low temperatures. The starter cultures were used in producing several different probiotic dairy foods. Under certain conditions probiotic strains may be used as the sole fermenting agent in milk. However, in many cases use of a support culture is preferable. Probiotic dairy products were shown to have good organoleptic properties, and the survival of the probiotic organisms was excellent during the shelf life of the products.

The technology of probiotics

Summary: Lactobacillus plantarum strain 4B2, which exhibits a strong autoaggregating phenotype, receives the broad-host-range plasmid pAMβ1 with conjugation efficiencies as high as 10-2 transconjugants per donor using solid matings; broth matings also occur, but at low transfer frequencies. Filter-sterilized spent supernatant of this strain contains a 32 kDa protein that promotes aggregation, and consequently a high frequency of conjugation, in lactic acid bacteria containing α-1,2-glucose-substituted lipoteichoic or teichoic acids. It appears, therefore, that the substituted lipoteichoic or teichoic acids act as receptors for the aggregation-promoting protein.

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High frequency of conjugation in Lactobacillus mediated by an aggregation-promoting factor

Molecular microbial analysis of Bifidobacterium isolates from different environments by the species-specific amplified ribosomal DNA restriction analysis (ARDRA).

A completely chemically-defined growth medium, containing guanine, thymine, cytidine, 2'-deoxyadenosine and 2'-deoxyuridine as DNA precursors, was developed for Lactobacillus johnsonii, on the basis of statistically designed techniques suitable for other lactobacilli. Particular focus was given to the nucleotide composition of different defined media, and to the specific nucleotide requirements of Lact. johnsonii. Most of the lactobacilli tested grew in a medium containing five free bases, four ribonucleosides or five deoxyribonucleosides. Adenine and guanine were replaceable by inosine. The requirement for thymine and cytosine was satisfied with uracil. The presence of inosine and uracil was identified as being essential for the growth of different Lactobacillus species, displaying their inability to synthesize purines and pyrimidines de novo. Defined recipes with different nucleotide composition were used to investigate iron requirements of lactobacilli. Only marginal differences in growth were observed in iron-depleted media supplemented with five free bases, four ribonucleosides or five deoxyribonucleosides; iron depletion had a greater effect on growth when inosine and uracil were supplied as the only nucleotide sources. The results suggest that iron plays a role in the pyrimidine and purine metabolism of lactobacilli. Lactobacillus spp., particularly Lact. johnsonii, require iron under particular environmental conditions with limited or specific nucleotide sources.

Roberto Reniero

Papers

Specific identification and targeted characterization of Bifidobacterium lactis from different environmental isolates by a combined multiplex-PCR approach.

The technology of probiotics

High frequency of conjugation in Lactobacillus mediated by an aggregation-promoting factor

Molecular microbial analysis of Bifidobacterium isolates from different environments by the species-specific amplified ribosomal DNA restriction analysis (ARDRA).

Iron requirement of Lactobacillus spp. in completely chemically defined growth media.