Effects of Salmonella Typhimurium Infection on the Gut Microbiota of Cherry Valley Meat Ducks.

Salmonella infection causes serious economic losses, threatens food safety, and is one of the most important diseases threatening meat duck farming. The gut microbiome is critical in providing resistance against colonization by exogenous microorganisms. Studying the relationship between Salmonella and gut microbiota can help us better understand the threat of the pathogenic mechanism of Salmonella and provide a more scientific theoretical basis for its prevention and treatment. This study uses Salmonella Typhimurium as the research object and Cherry Valley meat duck as the model with which to study the impact of Salmonella infection on ducks. In this field trial, 2 × 108 CFUs Salmonella Typhimurium were administered to 3-day-old ducks. After infection, duck viscera were collected to detect the colonization of Salmonella, and cecal contents were collected to analyze the changes in gut microbiota. The results show that Salmonella Typhimurium can colonize ducks three days after infection and alter the gut microbiota composition, mainly by increasing the abundance of Ruminococcaceae and Lachnospiraceae. In conclusion, Salmonella Typhimurium infection significantly alters the intestinal microbiota of ducks and poses a serious public health risk.

Nitrogen deposition enhances the deterministic process of the prokaryotic community and increases the complexity of the microbial co-network in coastal wetlands.

Global nitrogen deposition has increased significantly in recent years. At present, research on the effects of different amounts and types of nitrogen deposition on soil microorganisms in coastal wetlands is scarce. In this study, based on 7 years of simulated nitrogen deposition at multiple levels (low, medium, high) and of multiple types (NH4NO3, NH4Cl, KNO3), the effects of different nitrogen deposition conditions on the diversity, community assembly processes, co-networks, and community function of soil prokaryotes in coastal wetlands were examined. The results showed that, compared with that in control, the microbial α diversity increased significantly under nitrogen deposition (P < 0.05). However, it decreased significantly in the high-NH4NO3 and high-NH4Cl treatments (P < 0.05). The deterministic process of community assembly was strengthened under the different types of nitrogen deposition. Compared with that under NH4+-N deposition, the microbial co-network under NO3--N deposition was more complex. Network stability significantly decreased under different NH4+-N deposition levels. In addition, the results of FAPROTAX functional prediction showed that microbial community functional groups associated with carbon and nitrogen cycling changed significantly (P < 0.05). In conclusion, our results emphasize that nitrogen deposition environments cause changes in soil microbial community structure and interactions, and may also affect soil carbon and nitrogen cycling, but the effects of different forms and levels of nitrogen deposition are not consistent. This study provides new insights for evaluating the changes in soil microbial communities in coastal wetlands caused by different types of long-term nitrogen deposition, and has scientific significance for assessing the ecological effects of long-term nitrogen deposition.

Distinct distribution patterns of ammonia-oxidizing archaea and bacteria in sediment and water column of the Yellow River estuary.

Ammonia oxidation is a critical process of estuarine nitrogen cycling involving ammonia-oxidizing archaea (AOA) and bacteria (AOB). However, the distribution patterns of ammonia-oxidizing microorganisms (AOMs) between different habitats in the same area remain unclear. The present study investigated the AOMs' abundance and community compositions in both sediment and water habitats of the Yellow River estuary. Quantitative PCR (qPCR) revealed that AOA showed significant higher abundance than AOB both in sediment and water samples. AOA and AOB abundance distribution trends were consistent in sediment but distinct in water along the sampling sites. Clone library-based analyses showed that AOA sequences were affiliated with Nitrososphaera, Nitrosopumilus and Nitrosotalea clusters. Generally, Nitrososphaera was predominant in sediment, while Nitrosopumilus and Nitrosotalea dominated in water column. AOB sequences were classified into genera Nitrosospira and Nitrosomonas, and Nitrosospira dominated in both habitats. Principal coordinate analysis (PCoA) also indicated AOA community structures exhibited significant differences between two habitats, while AOB were not. Ammonium and carbon contents were the potential key factors to influence AOMs' abundance and compositions in sediment, while no measured variables were determined to have major influences on communities in water habitat. These findings increase the understanding of the AOMs' distribution patterns in estuarine ecosystems.

Distinct distribution patterns of proteobacterial nirK- and nirS-type denitrifiers in the Yellow River estuary, China.

Denitrification is considered to be the critical process in removing reactive nitrogen in estuarine ecosystems. In the present study, the abundance, diversity, and community structure of nirK- and nirS-type denitrifiers were compared in sediments from the Yellow River estuary. Quantitative polymerase chain reaction showed that the 2 types of denitrifiers exhibited different distribution patterns among the samples, indicating their distinct habitat preference. Phylogenetic analysis revealed that most of the sequences from clusters I, III, IV, and V for nirK-type denitrifiers were dominant and were distributed at sites where dissolved oxygen (DO) was lower, and the sequences in the other clusters were dominant at sites with higher DO. However, there was no spatially heterogeneous distribution for the nirS-type denitrifier community. Canonical correlation analysis and correlation analysis demonstrated that the community structure of nirK was more responsive to environmental factors than was that of nirS. Inversely, the abundance and α-diversity targeting nirS gene could be more easily influenced by environmental parameters. These findings can extend our current knowledge about the distribution patterns of denitrifying bacteria and provide a basic theoretical reference for the dynamics of denitrifying communities in estuarine ecosystem of China.