Browsing by Person "Tilocca, Bruno"

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Effects of diets with different phosporus availability on the intestinal microbiota of chickens and pigs
(2019) Tilocca, Bruno; Seifert, Jana
In the research works of the present thesis, 16S rRNA gene sequencing and metaproteomics were employed to investigate the gut microbiota of chickens and pigs kept at experimental diets with varying amount of calcium-phosphorus (CaP) and supplemented MP. This represents a valuable approach to investigate the bacterial specimens involved in the P absorption, allowing for a comprehensive understanding of how the intestinal bacteria adapt to a new diet and which metabolic routes are affected by changing levels of supplemented P and/or MP. Two major experimental trials were performed during the investigation. The first one was conducted on chickens operating a modulation in the dietary levels of Ca, P and MP. This trial highlighted a shift in the composition of the crop and ceca-associated microbial community depending on the composition of the diet fed. Also, investigated protein inventory revealed that the stress condition due to the reduced P availability is mirrored in the gastrointestinal tract (GIT)-associated microbiota. Marked differences were observed in the functions of the bacterial community in the case of P-available diets versus P-deficient ones. Protein repertoire of the first case draws a thriving microbial community focused on complex and anabolic functions. Contrariwise, the bacterial community in the case of P-lacking diets appears to deal with catabolic functions and stress response. The second trial was conducted on pigs and attempts to define the dynamics featuring the microbiota adaptation to a new challenging diet composed of different protein sources and varying levels of Ca and P. Statistical evidences reveal a stepwise adaptation of the fecal microbiota to the experimental diets fed. Both DNA-based approach and metaproteomics independently reveal three main adaptation phases: -before the feeding of the experimental trial (i.e. Zero), -the response of the microbial community to the challenging factor (i.e. MA) and, finally, - the newly achieved homeostatic balance (i.e. EQ). As observed in the first trial, feeding of the experimental diets impairs the overall fecal microbiota composition, stimulating the presence of phase-specific bacterial specimens and a characteristic relative abundance of the shared ones. Bacterial families responsible for the phase-specific architecture of the fecal microbiota are also active in the biochemical pathways driving the functional peculiarities of each adaptation phase. A deeper investigation of the identified protein repertoire revealed that the observed statistical differences among the adaptation phases are uniquely due to the Ca and P composition of the diets fed. None of the observed effects can be attributed to the diverse protein sources supplemented with the diets. Functional categorization of the identified protein inventory depicts three diverse functional assets of the microbial community. Specifically, prior the feeding of the experimental diets, bacteria are hypothesized to live under homeostatic condition, since they appear to be involved in complex and highly-specialized functions. Following the administration of the experimental diets microbial community changes its functional priority and reduce the expression of highly specialized functions to focus on more essential ones. Proteins involved in complex functions such as widening the substrates array and facing complex sugars tend to increase in abundance while the new homeostatic balance is achieved. Altogether, data from both trials provide useful information for future studies aimed to design effective breeding strategies finalized to reduce the P supplementation in the routinely breeding of livestock and maintain a balanced microbial activity in the animal GIT. Investigation of the dynamics of the porcine microbiota provides instructions on the minimal exposure time required from the intestinal microbiota to adapt to a new dietary composition. This is of fundamental importance for the design of future studies aimed to confirm and/or continue our results. Moreover, the anatomical and physiological similarities occurring between humans and pigs, make our findings of interest for future human nutritional studies, where the mechanisms and lasts of the microbiota adaptation process is still object of discussion.