The gut microbiota plays important roles in its host. However, how each microbiota member contributes to the behavior of the whole population is not known. In this study, we therefore determined protein expression in the cecal microbiota in chickens of selected ages and in 7-day-old chickens inoculated with different cecal extracts on the day of hatching. Campylobacter, Helicobacter, Mucispirillum, and Megamonas overgrew in the ceca of 7-day-old chickens inoculated with cecal extracts from donor hens. Firmicutes were characterized by ABC and phosphotransferase system (PTS) transporters, extensive acyl coenzyme A (acylCoA) metabolism, and expression of L-fucose isomerase. Anaerostipes, Anaerotruncus, Pseudoflavonifractor, Dorea, Blautia, and Subdoligranulum expressed spore proteins. Firmicutes (Faecalibacterium, Butyrivibrio, Megasphaera, Subdoligranulum, Oscillibacter, Anaerostipes, and Anaerotruncus) expressed enzymes required for butyrate production. Megamonas, Phascolarctobacterium, and Blautia (exceptions from the phylum Firmicutes) and all Bacteroidetes expressed enzymes for propionate production pathways. Representatives of Bacteroidetes also expressed xylose isomerase, enzymes required for polysaccharide degradation, and ExbBD, TonB, and outer membrane receptors likely to be involved in oligosaccharide transport. Based on our data, Anaerostipes, Anaerotruncus, and Subdoligranulum might be optimal probiotic strains, since these represent spore-forming butyrate producers. However, certain care should be taken during microbiota transplantation because the microbiota may behave differently in the intestinal tract of a recipient depending on how well the existing communities are established.

Studies analyzing the composition of gut microbiota are quite common at present, mainly due to the rapid development of DNA sequencing technologies within the last decade. This is valid also for chickens and their gut microbiota. However, chickens represent a specific model for host–microbiota interactions since contact between parents and offspring has been completely interrupted in domesticated chickens. Nearly all studies describe microbiota of chicks from hatcheries and these chickens are considered as references and controls. In reality, such chickens represent an extreme experimental group since control chicks should be, by nature, hatched in nests in contact with the parent hen. Not properly realising this fact and utilising only 16S rRNA sequencing results means that many conclusions are of questionable biological relevance. The specifics of chicken-related gut microbiota are therefore stressed in this review together with current knowledge of the biological role of selected microbiota members. These microbiota members are then evaluated for their intended use as a form of next-generation probiotics.

In commercial poultry production, there is a lack of natural flora providers since chickens are hatched in the clean environment of a hatchery. Events occurring soon after hatching are therefore of particular importance, and that is why we were interested in the development of the gut microbial community, the immune response to natural microbial colonization, and the response to Salmonella enterica serovar Enteritidis infection as a function of chicken age. The complexity of chicken gut microbiota gradually increased from day 1 to day 19 of life and consisted of Proteobacteria and Firmicutes. Salmonella enterica is one of the major causes of human food-borne gastroenteritis worldwide, and since poultry are considered to be the most important source of S. enterica for humans, measures of how to limit S. enterica prevalence in poultry are continuously being sought. The already-in-use measures aiming at the reduction of S. enterica prevalence in poultry include strict hygienic standards and vaccination with attenuated or inactivated vaccines. However, although hygienic standards are important for S. enterica control, at the same time, this represents an issue. Chickens for commercial production are hatched in a clean environment, and unlike all other farm animals, chickens will never get into contact with adult birds to become colonized by the healthy microflora of adults. Colonization of mucosal surfaces in newly hatched chickens is therefore a matter of coincidence, and if a bacterial pathogen appears in the environment, the sterile intestinal tract of a newly hatched chicken represents an empty ecological niche enabling such a pathogen essentially unrestricted multiplication followed by prolonged colonization. This is the reason why the use of competitive exclusion (CE) products enabling early rapid colonization of chickens with healthy adult gut microbiota has been successfully tested in poultry (18,20). The positive effect of CE products has been explained by the ability of bacteria present in these products to compete directly with pathogens and also to stimulate maturation of the gut immune system of newly hatched chickens.The interaction between the immune system of the gut and commensal microbiota in chickens starts immediately after hatching and leads to a low level of inflammation characterized by increased interleukin-8 (IL-8) expression (2). This results in the infiltration of heterophils and lymphocytes into the lamina propria or the gut epithelium and normalization of the gut immune system (3, 16, 30). Infiltrating lymphocytes develop further, depending on the gut flora composition, either in terms of a decreasing ratio of ␣␤ to ␥␦ T lymphocytes in the lamina propria or the gut epithelium (15) or in terms of changes in ␣␤ T-cell receptor repertoires (21). In mice, but not in chickens so far, gut microflora has been reported to induce the Th1 and Th17 arms of the immune response, with IL-17 playing an important role in the maturation of the murine gut immune system (9, 12). Interestingly, IL-17 has be...

In this study we characterised the development of caecal microbiota in egg laying hens over their commercial production lifespan, from the day of hatching until 60 weeks of age. Using pyrosequencing of V3/V4 variable regions of 16S rRNA genes for microbiota characterisation, we were able to define 4 different stages of caecal microbiota development. The first stage lasted for the first week of life and was characterised by a high prevalence of Enterobacteriaceae (phylum Proteobacteria). The second stage lasted from week 2 to week 4 and was characterised by nearly an absolute dominance of Lachnospiraceae and Ruminococcaceae (both phylum Firmicutes). The third stage lasted from month 2 to month 6 and was characterised by the succession of Firmicutes at the expense of Bacteroidetes. The fourth stage was typical for adult hens in full egg production aged 7 months or more and was characterised by a constant ratio of Bacteroidetes and Firmicutes formed by equal numbers of the representatives of both phyla.

No abstract