Variations in Marine Bacterial and Archaeal Communities during an Ulva prolifera Green Tide in Coastal Qingdao Areas

Changes in the structure of the microbial community within the phycospheric microenvironment and potential biogeochemical effects induced in the demise stage of green tides caused by Ulva prolifera

Green tides caused by Ulva prolifera occur annually in the Yellow Sea of China, and the massive amount of biomass decomposing during the demise stage of this green tide has deleterious ecological effects. Although microorganisms are considered key factors influencing algal bloom demise, an understanding of the microbial-algae interactions within the phycospheric microenvironment during this process is still lacking. Here, we focused on the variations in phycospheric microbial communities during the late stage of the green tide in three typically affected areas of the Yellow Sea via metagenomic sequencing analysis. In total, 16.9 million reads obtained from 18 metagenome samples were incorporated into the assembled contigs (13.4 Gbp). The phycosphere microbial community composition and diversity changed visibly during the demise of U. prolifera. The abundances of algae-lysing bacteria, Flavobacteriaceae at the family level and Alteromonas, Maribacter, and Vibrio at the genus level increased significantly in the phycosphere. In addition, the levels of glycoside hydrolases (GHs) and polysaccharide lyases (PLs) enzymes, which decompose U. prolifera polysaccharides in the phycosphere, were greater. Therefore, the degradation of algal polysaccharides can increase the efficiency of carbon metabolism pathways in the phycospheric microenvironment. Most of the genes detected in the phycosphere, especially norC, nrfA, and nasA, were associated with nitrogen metabolism pathways and showed dynamics related to the demise of the large amount of organic matter released by a green tide. Therefore, the demise of green tide algae may affect the potential carbon and nitrogen cycles of the phycospheric microenvironment by driving changes in the structure and diversity of microbial communities. Our research provides a novel perspective to better understand the ecological impact of U. prolifera during the green tide demise stage.

Behind the scenes: metagenomic analysis of bacterial communities in sustainable depilation of sheepskin

AIM

The leather industry is embracing eco-friendly technologies for both regulatory compliance and sustainable growth. While enzymatic depilation provides a greener alternative to traditional beamhouse methods, its complexity often leads to higher costs. To address this, we examined the performance of sheepskins' native bacterial flora in acetic acid conditions with low-environmental impact.

METHODS AND RESULTS

Utilizing metagenomic techniques, we analyzed the bacterial community dynamics during the depilation process. This investigation revealed a notable increase in microbial diversity and richness in acetic acid treatments compared to water treatments. At the class level, a post-processing decrease in Gammaproteobacteria dominance was observed, while Actinomycetia numbers surged in the acetic acid group. In contrast, the water group showed an increase in Bacteroidia. Order-level analysis indicated reductions in Pseudomonadales and increases in Actinomycetales with acetic acid treatment, whereas Flavobacteriales was more prevalent in water-treated liquors. At the family level, Moraxellaceae decreased and Micrococcaceae increased in the acetic acid group, in contrast to the marked rise of Weeksellaceae in the water group. Temporal analyses further highlighted the evolving bacterial landscapes under different treatments. Moreover, acetic acid treatment fostered a stable microbial community, beneficial for sustainable leather processing. Functional pathways were predicted using PICRUSt2. It showed that significantly enriched degradation pathways in the water group were less abundant in the acetic acid group, potentially preventing substrate matrix damage during depilation.

CONCLUSION

The study underscores the transformative potential of acetic acid for the leather industry, offering a pathway to reduce pollution while maintaining economic viability. By enhancing our understanding of microbial interactions during depilation, this study opens avenues for refining these eco-friendly techniques. Our findings advocate for a shift towards greener depilation methods and contribute to the broader dialogue on sustainable manufacturing practices, emphasizing the importance of leveraging indigenous microbial communities for environmental and economic gains.

A novel flavobacterial phage abundant during green tide, representing a new viral family, Zblingviridae

Flavobacteriia are the dominant and active bacteria during algal blooms and play an important role in polysaccharide degradation. However, little is known about phages infecting Flavobacteriia, especially during green tide. In this study, a novel virus, vB_TgeS_JQ, infecting Flavobacteriia was isolated from the surface water of the Golden Beach of Qingdao, China. Transmission electron microscopy demonstrated that vB_TgeS_JQ had the morphology of siphovirus. The experiments showed that it was stable from -20°C to 45°C and pH 5 to pH 8, with latent and burst periods both lasting for 20 min. Genomic analysis showed that the phage vB_TgeS_JQ contained a 40,712-bp dsDNA genome with a GC content of 30.70%, encoding 74 open-reading frames. Four putative auxiliary metabolic genes were identified, encoding electron transfer-flavoprotein dehydrogenase, calcineurin-like phosphoesterase, phosphoribosyl-ATP pyrophosphohydrolase, and TOPRIM nucleotidyl hydrolase. The abundance of phage vB_TgeS_JQ was higher during Ulva prolifera (U. prolifera) blooms compared with other marine environments. The phylogenetic and comparative genomic analyses revealed that vB_TgeS_JQ exhibited significant differences from all other phage isolates in the databases and therefore was classified as an undiscovered viral family, named Zblingviridae. In summary, this study expands the knowledge about the genomic, phylogenetic diversity and distribution of flavobacterial phages (flavophages), especially their roles during U. prolifera blooms.

IMPORTANCE

The phage vB_TgeS_JQ was the first flavobacterial phage isolated during green tide, representing a new family in Caudoviricetes and named Zblingviridae. The abundance of phage vB_TgeS_JQ was higher during the Ulva prolifera blooms. This study provides insights into the genomic, phylogenetic diversity, and distribution of flavophages, especially their roles during U. prolifera blooms.

Spatial and diel variations of bacterioplankton and pico-nanoeukaryote communities and potential biotic interactions during macroalgal blooms

We investigated spatial heterogeneity and diel variations in bacterioplankton and pico-nanoeukaryote communities, and potential biotic interactions at the extinction stage of the Ulva prolifera bloom in the Jiaozhou Bay, Yellow Sea. It was found that the presence of Ulva canopies significantly promoted the cell abundance of heterotrophic bacteria, raised evenness, and altered the community structure of bacterioplankton. A diel pattern was solely significant for pico-nanoeukaryote community structure. >50 % of variation in the heterotrophic bacterial abundance was accounted for by the ratio of Bacteroidota to Firmicutes, and dissolved organic nitrogen effectively explained the variations in cell abundances of phytoplankton populations. The factors representing biotic interactions frequently contributed substantially more than environmental factors in explaining the variations in diversity and community structure of both bacterioplankton and pico-nanoeukaryotes. There were higher proportions of eukaryotic pathogens compared to other marine systems, suggesting a higher ecological risk associated with the Ulva blooms.

Metatranscriptomic insights into the microbial metabolic activities during an Ulva prolifera green tide in coastal Qingdao areas

Green tide, a typical marine environmental disaster that profoundly influenced the coastal areas, has been occurred consecutively in the South Yellow Sea of China since 2007. Herein, the active microbial community structure and metabolic pathways in Qingdao offshore during an Ulva prolifera green tide were investigated by using metatranscriptomic approach. The dominant active microbial taxa at the outbreak phase were primarily a functional group that can utilize organic matters derived from U. prolifera, such as Lentibacter, Polaribacter and Planktomarina. While the taxa involved in biogeochemical cycles, including Phaeobacter, Pseudomonas and Marinobacterium, dominated the active microbial communities at the decline phase. The expression level of enzymes involved in U. prolifera polysaccharides degradation was significantly higher at the outbreak phase compared to the decline phase. At the same time, the main players Glaciecola and Polarbacter showed similar trends, suggesting that the low competitiveness for nutrients of related microorganisms at this phase made them degrade more U. prolifera polysaccharides to meet their own nutrient needs, thereby accelerating the degradation of U. prolifera. According to KEGG annotation, the biogeochemical pathways including nitrogen cycle, sulfur cycle and methane oxidation altered during the green tide, with thiosulfate oxidation and methane oxidation probably being the crucial pathways at the outbreak and the decline phase respectively. The coupling of sulfide oxidation and denitrification was also observed in this study. Furthermore, the green tide in Qingdao offshore might impact the greenhouse effects induced by CH4 and N2O through influencing the related microbial processes.

Virome reveals effect of Ulva prolifera green tide on the structural and functional profiles of virus communities in coastal environments

Viruses are widely distributed in marine environments, where they influence the transformation of matter and energy by modulating host metabolism. Driven by eutrophication, green tides are a rising concern in Chinese coastal areas, and are a serious ecological disaster that negatively affects coastal ecosystems and disrupts biogeochemical cycles. Although the composition of bacterial communities in green algae has been investigated, the diversity and roles of viruses in green algal blooms are largely unexplored. Therefore, the diversity, abundance, lifestyle, and metabolic potential of viruses in a natural bloom in Qingdao coastal area were investigated at three different stages (pre-bloom, during-bloom, and post-bloom) by metagenomics analysis. The dsDNA viruses, Siphoviridae, Myoviridae, Podoviridae, and Phycodnaviridae, were found to dominate the viral community. The viral dynamics exhibited distinct temporal patterns across different stages. The composition of the viral community varied during the bloom, especially in populations with low abundance. The lytic cycle was most predominant, and the abundance of lytic viruses increased slightly in the post-bloom stage. The diversity and richness of the viral communities varied distinctly during the green tide, and the post-bloom stage favored viral diversity and richness. The total organic carbon, dissolved oxygen, NO^3-, NO^2-, PO₄^3-, chlorophyll-a contents, and temperature variably co-influenced the viral communities. The primary hosts included bacteria, algae, and other microplankton. Network analysis revealed the closer links between the viral communities as the bloom progressed. Functional prediction revealed that the viruses possibly influenced the biodegradation of microbial hydrocarbons and carbon by metabolic augmentation via auxiliary metabolic genes. The composition, structure, metabolic potential, and interaction taxonomy of the viromes differed significantly across the different stages of the green tide. The study demonstrated that the ecological event shaped the viral communities during algal bloom, and the viral communities played a significant role in phycospheric microecology.