Browsing by Subject "Metaproteomics"

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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.
Metaomic studies of the dietary impact on the structural and functional diversity of the rumen microbiome
(2018) Deusch, Simon; Seifert, Jana
Ruminant production efficiency and related emission of greenhouse gases are mainly determined by the rumen microbiome. The structure and activity of the microbial communities in turn are mostly influenced by the animal’s feed intake. The most widely used forage sources for ruminant production in Europe are corn silage, grass silage and grass hay. Progress in animal production requires optimized feeding strategies which presuppose an improved understanding of the dietary impact on the complex bionetwork residing in the rumen. A broad range of different methods are applicable to investigate archaea and bacteria which represent the most active members of the rumen microbiome. Most rumen studies available are restricted to nucleic acid-based approaches with limited functional insights. To improve knowledge about the prokaryotic communities and their adaptation responses to different animal feeds, it is essential to focus on the actual functions out of numerous possibilities that are encoded by the genomes of the rumen microbiome. Therefore proteins are best suited since representing the actual function of investigated cells combined with phylogenetic information. The major aim of this project was the feasible, first-time establishment of a metaproteomics-based characterization of the ruminal prokaryotic communities to further investigate the dietary impact on the prokaryotic rumen metaproteome. The first part was providing an overview about research that used state of the art technologies to investigate the microbiome of the gastrointestinal tract of farm animals. Yet, Omics-technologies and their combination are rarely employed in livestock science. The considered studies relied mainly on stand-alone, DNA-based molecular methods which clearly emphasized the importance of introducing contemporary methods such as shotgun metaproteomics to study the rumen microbiome and to gain deeper, more complete insights into the actual functions carried out by the specific members of the prokaryotic communities. The second part of the current project focused on a suitable, mass spectrometry-based analysis of the prokaryotic communities in the rumen ecosystem. Metaproteomic studies are challenged by the heterogeneity of the rumen sample matter that contains, besides archaeal and bacterial cells, also eukaryotic cells of rumen fungi and protozoa as well as enormous amounts of plant cells from ingested feed and epithelial cells of the animals. Shotgun metaproteomic studies require the extraction of proteins preferably of the desired target organisms to increase the coverage of the respective metaproteome and the reliability of subsequent protein identifications. This entails the avoidance of undesired proteins present in the rumen samples. In contrast to nucleic acids, proteins cannot be enriched or amplified by PCR thus, optimized sample preparation protocols are necessary in order to retrieve enhanced amounts of prokaryotic instead of plant-derived or other eukaryotic cells before protein extraction and subsequent LC-MS/MS analysis. The final step and the major aim of this project was the in depth analysis of the metaproteome of archaea and bacteria and their adaptive response to the most common forages, corn silage, grass silage and grass hay accessing as well host-related influences and variations between different ecological niches within the rumen. Improved mass-spectrometric measurements and the construction of a customized, sample-specific in-house database for enhanced bioinformatic quantification of proteins yielded comprehensive datasets comprising 8,163 bacterial and 358 archaeal proteins that were identified across 27 samples from three different rumen fractions of three Jersey cows, fed rotationally with three different diets. The functional and structural data of the metaproteomic analysis was further flanked by 16S rRNA gene-based analyses of the archaeal and bacterial community structures and the metabolomes of the rumen fluid fractions were quantified by nuclear magnetic resonance. So far, to the best of our knowledge, there are no studies investigating the metaproteome expressed by the entirety of archaeal and bacterial communities in the different phases of the rumen ecosystem under varying dietary influence. Dietary treatments revealed significant variations in the metaproteome composition and community structures of ruminal bacteria. Host-related effects were not significant. In conclusion, within this project the application of shotgun metaproteomics to characterize the prokaryotic rumen metaproteome was successfully implemented and the obtained results clearly emphasized the benefits of using complementary, state of the art methods to study the microbiome of complex ecosystems like the rumen. Considering the specific functional niches of the rumen microbiome have been shown to be of great importance.