[Mechanism of Algal Community Dynamics Driven by the Seasonal Water Bacterial Community in a Stratified Drinking Water Reservoir].

Phytoplankton and bacteria are crucial components of aquatic food webs, playing critical roles in the structure and function of freshwater ecosystems. However, there are few studies on how the algal and bacterial communities interact and respond to changing environmental conditions in the water reservoirs. Thus, the ecological interaction relationship between the temporal succession of the phytoplankton community and the bacterial community was investigated using 16S rDNA high-throughput sequencing and a co-occurrence network in the Lijiahe Reservoir. The results showed that Bacillariophyta and Chlorophyta were also dominant taxa in the phytoplankton community. In August, Cyanobacteria replaced Bacillariophyta as the second-most dominant taxa, with an average relative abundance of 30.13%. DNA sequencing showed that Proteobacteria, Actinobacteria, and Bacteroidetes dominated throughout the year. Proteobacteria reached a maximum relative abundance of 71.68% in July. Acidobacteria and Deinococcus-Thermus, which were rare taxa, reached maximum relative abundances of 10.20% and 5.56%, respectively. The co-occurrence network showed that the association between algae and bacteria was mainly positive, indicating that the interaction between them may be dominated by mutualism. As a keystone taxa, Methylotenera was significantly and positively related to Chlorella. Scenedesmus was also a keystone taxa and was significantly and negatively correlated with various bacteria, such as Methylobacter, Solitalea, and Rhodoferax. An RDA analysis showed that the succession of algal and bacterial communities was significantly regulated by water temperature, pH, and conductivity, and the environmental factors explained 93.1% and 90% of the variation in the algal community and bacterial community, respectively. The results will provide a scientific basis for exploring the micro-ecological driving mechanism of the interaction between algae and bacteria in deep drinking water reservoir ecosystems.

Effectiveness of inactivated SARS-CoV-2 vaccines against the Delta variant infection in Guangzhou: a test-negative case-control real-world study.

The effectiveness of inactivated SARS-CoV-2 vaccines against the Delta variant, which has been associated with greater transmissibility and virulence, remains unclear. We conducted a test-negative case-control study to explore the vaccine effectiveness (VE) in real-world settings. We recruited participants aged 18-59 years who consisted of SARS-CoV-2 test-positive cases (n = 74) and test-negative controls (n = 292) during the outbreak of the Delta variant in May 2021 in Guangzhou city, China. Vaccination status was compared to estimate The VE of SARS-CoV-2 inactivated vaccines. A single dose of inactivated SARS-CoV-2 vaccine yielded the VE of only 13.8%. After adjusting for age and sex, the overall VE for two-dose vaccination was 59.0% (95% confidence interval: 16.0% to 81.6%) against coronavirus disease 2019 (COVID-19) and 70.2% (95% confidence interval: 29.6-89.3%) against moderate COVID-19 and 100% against severe COVID-19 which might be overestimated due to the small sample size. The VE of two-dose vaccination against COVID-19 reached 72.5% among participants aged 40-59 years, and was higher in females than in males against COVID-19 and moderate diseases. While single dose vaccination was not sufficiently protective, the two-dose dosing scheme of the inactivated vaccines was effective against the Delta variant infection in real-world settings, with the estimated efficacy exceeding the World Health Organization minimal threshold of 50%.

[Water Quality and Bacterial Population Driving Mechanism of Algae Vertical Succession in Stratified Reservoir].

Phytoplankton and bacteria are important components of the aquatic food web, and play a critical role in substance circulation and energy exchange in freshwater ecosystems. The succession of algae is closely related to the metabolism and structural succession of bacterial populations in the water column. Thus, in this study, the vertical succession characteristics of phytoplankton and bacteria community structure and their coupling with water quality were investigated during an algal bloom in the Lijiahe Reservoir using high-throughput DNA sequencing and Biolog technologies. The results showed that the Lijiahe Reservoir was in the thermal stratification stage in August, and the pH, dissolved oxygen, and NH4+-N of the water column gradually decreased with depth (P<0.001). Algal cell concentration and chlorophyll a exhibited a simultaneous trend (P<0.001), and the maximum values in the surface layer were 3363.33×104 cells·L-1 and 7.03 µg·L-1, respectively. The algal community structure was dominated by Microcystis at water depths of 0 m and 3 m, and at 6 m water depth, Cyclotella replaced Microcystis as the most dominant algae, with a relative abundance of 57.28%. Biolog analysis indicated that the outbreak of Microcystis had a significant impact on bacterial metabolic activity and its relative abundance, but the diversity of bacterial population metabolic activity varied less. A total of 1420 operational taxonomic units were found by high-throughput sequencing, belonging to 10 bacterial phyla. Of these, Actinobacteria and Proteobacteria dominated in all water layers, and their relative abundances were more than 50%. The relative abundance of Chlorobi and Planctomycetes varied significantly with water depth, reaching their maxima at a depth of 6 m with values of 10.29% and 6.78%, respectively, which were both negatively correlated with algal density (P<0.05). Firmicutes and Gemmatimonadetes were positively correlated with algal density (P<0.05). A heat map fingerprint showed that the vertical distribution of the bacterial community structure of the Lijiahe Reservoir varied significantly, and with the increase in water depth, the bacterial community was more uniformly distributed and tended to diversify. Redundancy analysis (RDA) showed that the vertical distribution of the bacterial and algal community structure was regulated by different water qualities, and the difference was significant. This study investigated the coupling mechanism of algal and bacterial communities during the algal bloom in the Lijiahe Reservoir, and the results provided a scientific basis for the investigation of the molecular microecological driving mechanism of water-source algal blooms.

[Advances in Microbe-Derived Taste and Odor Compounds in Typical Aquatic Ecosystems].

Olfactory microorganisms mainly include actinomycetes, algae, and myxobacteria, and are widely found in typical water ecosystems such as water source reservoirs, lakes, streams, and oceans. Biologically-derived taste and odor compounds can cause severe off-flavor problems at trace concentrations, threatening the safety of water supplies. Physical and chemical methods have been implemented, but they need to be improved and optimized. Microbial methods show attractive prospects due to their environmentally friendly characteristics. This article reviews the literature regarding the types, biological sources, detection methods, control measures, influencing factors, and odor-producing mechanisms of microbial methods. Future research directions and fields of investigation are discussed in order to promote the related research of taste and odor compounds and ensure the safety of urban water supplies.

[Spatial and Temporal Succession Characteristics of Aerobic Anoxygenic Photosynthesis Bacteria in a Stratified Reservoir].

Aerobic anoxygenic photosynthesis bacteria (AAPB) play a significant role in the material circulation of the hydrosphere, with diverse community structure and unique metabolic functions. To investigate the spatial and temporal succession characteristics of AAPB abundance and community structure in Jinpen Reservoir, a quantitative real-time polymerase chain reaction and Illumina MiSeq high-throughput sequencing technique targeting the pufM gene were applied. Furthermore, redundancy analysis was used to determine the influence of environmental factors on their community structure. The results showed that the AAPB abundance ranged from (6.70±0.43)×103 to (2.69±0.15)×104 copies·mL-1, with the maximum value appearing in October, and decreased with an increase in water depth. Samples were mainly classified into 19 genera (except for the unclassified genus); the most abundant AAPB genera were Bradyrhizobium sp. and Methylobacterium sp., which were affiliated to the α-Proteobacteria, and the proportion of the Bradyrhizobium sp. was highest in November, accounting for more than 60% (except 10 m). Furthermore, Rubrivivax sp., belonging to ß-Proteobacteria, was found to have a low proportion. There was a strong interaction relationship between AAPB genera. For example, Rhodobacter sp. was positively correlated with Rhodovulum sp., while Hydrogenophaga sp. was negatively correlated with Bradyrhizobium sp.. The community structure composition and distribution of AAPB were significantly different, mainly affected by temperature (T), total nitrogen (TN), NO3--N, and light intensity and comprehensively regulated by environmental factors. For instance, T, TN, and total phosphorus had a significant impact on the AAPB community structure of water samples at 0, 5, and 15 m in October, whereas light intensity, pH, DO, and chlorophyll-a were major structuring factors in the AAPB assemblages of water samples at 5 m in December. The results have guiding significance for parsing the spatial and temporal variability of AAPB abundance and diversity in stratified reservoirs, and simultaneously provide a theoretical basis for exploring the driving factors of AAPB population structure.