As a dominant species among marine yeasts, Rhodotorula benthica accounts for ~50% of all marine yeasts. Rhodotorula is rich in a variety of bioactive substances and commonly used in the production of carotenoids by microbial fermentation and is worth developing. Therefore, the present study used a strain of Rhodotorula mucilaginosa isolated from the coastal waters of the South China Sea as the target yeast to investigate its impact on the immune function and gut microbiota of mice. A total of 200 mice were randomly divided into gavage groups and control group and garaged for 30 consecutive days at different concentration. Samples were collected on day 15 and day 30 of gavage administration. The results showed that R. mucilaginosa ZTHY2 could increase the thymus and spleen indices of mice, and its effect on the thymus index was more significant after long-term gavage administration. Short-term (15 days) gavage administration of R. mucilaginosa suspension enhanced delayed hypersensitivity in mice, increased serum IgG, IgA, and IL-2. Long-term (30 days) gavage administration of R. mucilaginosa suspension significantly enhanced the phagocytosis of macrophages in mice and significantly increased serum TNF-α and INF-γ. R. mucilaginosa ZTHY2 altered the structure of the gut microbiota of mice at the phylum and genus levels, leading to an increased relative abundance of Firmicutes and Lactobacillus and a decreased relative abundance of Bacteroidetes. This strain increased the beneficial intestinal bacteria and reduced the harmful intestinal bacteria in mice. This study provides experimental evidence and lays the foundation for the future development and application of this strain as a microecological source of carotenoids.

H6 subtype avian influenza viruses are globally distributed and, in recent years, have been isolated with increasing frequency from both domestic and wild bird species as well as infected humans. Many reports have examined the viruses in the context of poultry or several wild bird species, but there is less information regarding their presence in migratory birds. Hemagglutination and hemagglutination inhibition tests were used to measure HA activity for different HA subtypes. Whole viral genomes were sequenced and analysed using DNAstar and MEGA 6 to understand their genetic evolution. Pathogenicity was evaluated using a mouse infection model. We isolated 13 strains of H6 virus from faecal samples of migratory waterfowl in Anhui Province of China in 2014. Phylogenetic analysis showed gene reassortment between Eurasian and North American lineages. Five of the identified H6 strains had the ability to infect mice without adaptation. Our findings suggest that regular surveillance of wild birds, especially migratory birds, is important for providing early warning and control of avian influenza outbreaks.

The H6 subtype of avian influenza virus (H6 AIV) is the most detected AIV subtype in poultry and wild birds. It causes economic losses to the poultry industry, and the most important, H6 AIV may have the ability to infect mammals, which is a great threat to public health security. In addition, the H6 subtype can serve as a precursor to providing internal genes for other highly pathogenic AIVs, posing a potential threat. H6 AIV currently face to the high positive detection rate and harmless nature of H6 AIV and because not highly effective H6 subtype vaccine available on the market. In this study, we focused on the prevalence of H6 AIV in poultry and wild birds, phylogenetic analysis, genetic variation characteristics, selection analysis, and prevention and control to provide relevant references for the scientific prevention and control of H6 AIV in future.

As the natural hosts of avian influenza viruses (AIVs), aquatic and migratory birds provide a gene pool for genetic transfer among species and across species, forming transient “genome constellations.” This work describes the phylogenetic dynamics of H1NX based on the complete molecular characterization of eight genes of viruses that were collected from 2014 to 2015 in Anhui Province, China. Hemagglutination and hemagglutination inhibition tests were used to determine the hemagglutination (HA) activity of the HA subtypes. The entire genomes of the viruses were sequenced on an ABI PRISM 3500xl DNA Analyzer. The sequences were genetically analysed to study their genetic evolution using DNASTAR and MEGA 6. The pathogenic effects of the viruses were evaluated using mouse infection models. Seven strains of the H1 subtype avian influenza virus were isolated. Phylogenetic analysis indicated natural recombination of the H1 influenza viruses between the Eurasian lineage and the North American lineage. Some genes had high sequence identity with A/bean goose/Korea/220/2011(H9N2), which is a typical case involving viral reassortment between the Eurasian lineage and the North American lineage. The results of infection experiments in mice showed that the viruses could acquire the ability to multiply in mouse respiratory organs without adaptation. These findings suggest that continued surveillance of wild birds, particularly migratory birds, is important to provide early warning of possible H1 influenza epidemics and to understand the ecology of the virus.

H4Nx avian influenza viruses (AIVs) have been isolated from wild birds and poultry and can also cross the species barrier to infect mammals (pigs and muskrats). The widespread presence of these viruses in wild birds and poultry and their ability to be transmitted interspecies make them an undeniable hazard to the poultry farming industry. In the present study, we collected fecal and swab samples from wild birds and poultry in Guangdong Province from January 2019 to March 2024, and various subtypes of AIVs were isolated, including 19 strains of H4 subtype AIVs. Further analysis was conducted on the internal genes of the 19 strains. These strains clustered together with high homology to highly pathogenic avian influenza virus (HPAIV), suggesting that H4Nx AIV may be reassorted from HPAIV. Two H4N8 strains are phylogenetically related to the porcine H4N8 AIV. Molecular characterization revealed that all viruses in this study were less pathogenic but had potential mammalian-adapted mutations. The transmission dynamics of H4Nx AIVs revealed that Europe and Asia, especially the Netherlands and Bangladesh, may be the centers of transmission. This may be linked to the migration of wild birds. The high migration rates from Russia to the Netherlands and from Russia to Bangladesh may also play a role. Therefore, continuous and systematic monitoring of wild birds to clarify the spatial and temporal distribution and prevalence of influenza viruses in wild birds is significant for early warning of avian influenza outbreaks in poultry and for risk assessment for public health and safety.

Avian paramyxoviruses (APMVs) belong to the subfamily Avulavirinae of the family Paramyxoviridae and include 22 distinct subtypes or serotypes (1-22). Avian paramyxovirus serotype 12 (APMV-12) is found sporadically in wild birds worldwide, and reports from only Italy and Taiwan have been published to date; information on its genetic variation and biological characteristics is still limited. In this study, three APMV-12 strains, designated WB19, LY9, and LY11, were isolated from 8643 wild bird faecal samples during the annual influenza virus surveillance of wild birds in Guangdong, China between 2018 and 2024. which is first reported in mainland China. The complete genomes of the three viruses with six gene segments, 3′-N-P-M-F-HN-L-5′, were 15,231 nt in length. Phylogenetic analysis based on the whole genome showed that the three APMV-12 strains had the highest homology with an APMV-12 strain isolated from Taiwan in 2015, followed by the prototype APMV-12 strains isolated from mallard ducks in Italy in 2005. Genetic analysis of the whole gene of each of them indicated that they were derived from a Eurasian lineage. This study provides additional evidence that wild birds transmit viruses between countries, and this should be monitored to understand APMV transmission, evolution and epidemiology.