Seifert, Jana

AbstractStrategies to increase the production rate of chicken for human consumption alter the natural process of microbial colonisation and the nutritional performance of the animal. The lack of sufficient reference genomes limits the interpretation of sequencing data and restrain the study of complex functions. In this study, 43 strains obtained from crop, jejunum and ileum of chicken were isolated, characterised and genome analysed to observe their metabolic profiles, adaptive strategies and to serve as future references. Eight isolates represent new species that colonise the upper gut intestinal tract and present consistent adaptations that enable us to predict their ecological role, expanding our knowledge on the adaptive functions. Molecular characterisation confirmed the classification ofClostridium anaeroviscerissp. nov. (DSM 113860= LMG 32675),Clostridium butanolproducens(DSM 115076= LMG 32878),Ligilactobacillus hohenheimiussp. nov. (DSM 113870= LMG 32876),Limosilactobacillus gallussp. nov. (DSM 113833 =LMG 32623),Limosilactobacillus aviumsp. nov. (DSM 113849= LMG 32671), Limosilactobacillus pullumsp. nov. (DSM 115077 =LMG 32877),Limosilactobacillus digestussp. nov. (DSM113835= LMG 32625) andLimosilactobacillus difficilesp. nov. (DSM 114195= LMG 32875). Strains ofLimosilactobacilluswere found to be more abundant in the crop, whileLigilactobacillusdominated the ileal digesta. Isolates from crop encode a high number of glycosidases specialized in complex polysaccharides compared to strains isolated from jejunum and ileum. These results represent the first approach for the isolation and detection of bacteria from the chicken’s upper digestive tract and describe the functional diversity of bacteria inhabiting these regions, improving the potential handling of chicken microbiota with biotechnological applications.

ABSTRACT Nitrospirae spp. distantly related to thermophilic, sulfate-reducing Thermodesulfovibrio species are regularly observed in environmental surveys of anoxic marine and freshwater habitats. Here we present a metaproteogenomic analysis of Nitrospirae bacterium Nbg-4 as a representative of this clade. Its genome was assembled from replicated metagenomes of rice paddy soil that was used to grow rice in the presence and absence of gypsum (CaSO 4 ·2H 2 O). Nbg-4 encoded the full pathway of dissimilatory sulfate reduction and showed expression of this pathway in gypsum-amended anoxic bulk soil as revealed by parallel metaproteomics. In addition, Nbg-4 encoded the full pathway of dissimilatory nitrate reduction to ammonia (DNRA), with expression of its first step being detected in bulk soil without gypsum amendment. The relative abundances of Nbg-4 were similar under both treatments, indicating that Nbg-4 maintained stable populations while shifting its energy metabolism. Whether Nbg-4 is a strict sulfate reducer or can couple sulfur oxidation to DNRA by operating the pathway of dissimilatory sulfate reduction in reverse could not be resolved. Further genome reconstruction revealed the potential to utilize butyrate, formate, H 2 , or acetate as an electron donor; the Wood-Ljungdahl pathway was expressed under both treatments. Comparison to publicly available Nitrospirae genome bins revealed the pathway for dissimilatory sulfate reduction also in related Nitrospirae recovered from groundwater. Subsequent phylogenomics showed that such microorganisms form a novel genus within the Nitrospirae , with Nbg-4 as a representative species. Based on the widespread occurrence of this novel genus, we propose for Nbg-4 the name “ Candidatus Sulfobium mesophilum,” gen. nov., sp. nov. IMPORTANCE Rice paddies are indispensable for the food supply but are a major source of the greenhouse gas methane. If it were not counterbalanced by cryptic sulfur cycling, methane emission from rice paddy fields would be even higher. However, the microorganisms involved in this sulfur cycling are little understood. By using an environmental systems biology approach with Italian rice paddy soil, we could retrieve the population genome of a novel member of the phylum Nitrospirae . This microorganism encoded the full pathway of dissimilatory sulfate reduction and expressed it in anoxic paddy soil under sulfate-enriched conditions. Phylogenomics and comparison to the results of environmental surveys showed that such microorganisms are actually widespread in freshwater and marine environments. At the same time, they represent an undiscovered genus within the little-explored phylum Nitrospirae . Our results will be important for the design of enrichment strategies and postgenomic studies to further understanding of the contribution of these novel Nitrospirae spp. to the global sulfur cycle.

AbstractNitrospiraespp. distantly related to thermophilic, sulfate-reducingThermodesulfovibriospecies are regularly observed in environmental surveys of anoxic marine and freshwater habitats. However, little is known about their genetic make-up and physiology. Here, we present the draft genome ofNitrospiraebacterium Nbg-4 as a representative of this clade and analyzed itsin situprotein expression under sulfate-enriched and sulfate-depleted conditions in rice paddy soil. The genome of Nbg-4 was assembled from replicated metagenomes of rice paddy soil that was used to grow rice plants in the presence and absence of gypsum (CaSO4×2H2O). Nbg-4 encoded the full pathway of dissimilatory sulfate reduction and showed expression thereof in gypsum-amended anoxic bulk soil as revealed by parallel metaproteomics. In addition, Nbg-4 encoded the full pathway of dissimilatory nitrate reduction to ammonia, which was expressed in bulk soil without gypsum amendment. The relative abundance of Nbg-4-related metagenome reads was similar under both treatments indicating that it maintained stable populations while shifting its energy metabolism. Further genome reconstruction revealed the potential to utilize butyrate, formate, H2, or acetate as electron donor, with the Wood-Ljungdahl pathway being expressed under both conditions. Comparison to publicly availableNitrospiraegenome bins confirmed that the pathway for dissimilatory sulfate reduction is also present in relatedNitrospiraerecovered from groundwater. Subsequent phylogenomics showed that such microorganisms form a novel genus within the phylumNitrospirae, with Nbg-4 as a representative species. Based on the widespread occurrence of this novel genus, we propose for Nbg-4 the nameCandidatusSulfobium mesophilum, gen. nov., spec. nov.ImportanceRice paddies are indispensable for food supply but are a major source of the greenhouse gas methane. If not counterbalanced by cryptic sulfur cycling, methane emission from rice paddy fields would be even higher. However, the microorganisms involved in this sulfur cycling are little understood. By using an environmental systems biology approach of Italian rice paddy soil, we could retrieve the population genome of a novel member of the phylumNitrospirae. This microorganism encoded the full pathway of dissimilatory sulfate reduction and expressed itin situunder sulfate-enriched and anoxic conditions. Phylogenomics and comparison to environmental surveys showed that such microorganisms are actually widespread in freshwater and marine environments. At the same time, they represent a yet undiscovered genus within the little exploredNitrospirae. Our results will be important to design enrichment strategies and postgenomic studies to fully understand the contribution of these novelNitrospiraeto the global sulfur cycle.