Comparison in structure and predicted function of epiphytic bacteria on Neopyropia yezoensis and Neopyropia katadae

The economic alga Neopyropia,which holds significant value in China for its edibility and economic potential,harbors diverse epiphytic bacteria on its surface.The epiphytic bacteria on Neopyropia yezoensis and Neopyropia katadae,two nori species of Neopyropia living at the same tidal level but with distinct physiological states and living habits,were investigated to understand the differences between them and the effects of epiphytic bacteria on their differential characteristics.Analysis of 16S rRNA gene sequences and real-time quantitative PCR(qPCR)of thalli and seawater samples(n=24)revealed notable differences in microbial diversity and community structure between the two species.Bacteroidetes dominated the bacterial communities in association with N.yezoensis,whereas Proteobacteria were predominant in N.katadae.Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt2)analysis revealed enriched genes that related to the ABC transport system,iron complex outer membrane receptor proteins,and proliferation in N.yezoensis,whereas N.katadae exhibited enrichment of genes that related to energy supply as well as cell wall and cell membrane production.The results of qPCR indicate a higher abundance of epiphytic bacteria on surface of N.yezoensis than those on surface of N.katadae.The findings indicate that differences in the living environments of N.yezoensis and N.katadae may result in distinct structural composition and abundance of epiphytic bacteria on their surfaces,thereby conferring specific biological functionalities to each microbial community,and the epiphytic bacteria may shape the living habits of hosts to some extents.This study provided a basis for understanding the close association between surface microorganisms and algal bodies,and the physiological and ecological characteristics of nori species.

Host plant traits play a crucial role in shaping the composition of epiphytic microbiota in the arid desert,Northwest China

Phyllosphere microorganisms are a crucial component of environmental microorganisms,highly influenced by host characteristics,and play a significant role in plant health and productivity.Nonetheless,the impact of host characteristics on shaping phyllosphere microbial communities of plants with different life forms remains ambiguous.Utilizing high-throughput sequencing technology,this study analyzed the diversity and community composition of phyllosphere epiphytic microorganisms(e.g.,bacteria and fungi)of various plant life forms in the hinterland of the Gurbantunggut Desert,Northwest China.Functional annotation of prokaryotic taxa(FAPROTAX)and fungi function guild(FUNGuild)were employed to assess the ecological functions of microorganisms and to investigate the role of stochastic and deterministic processes in shaping phyllosphere microbial communities.Result showed a diverse array of phyllosphere epiphytic microorganisms in the desert plants,with Proteobacteria,Cyanobacteria,and Actinobacteriota dominating bacterial community,while Ascomycota and Basidiomycota were prevalent in fungal community.Comparison across different plant life forms highlighted distinct microbial communities,indicating strong filtering effects by plant characteristics.FAPROTAX prediction identified intracellular parasites(accounting for 27.44%of bacterial community abundance),chemoheterotrophy(10.12%),and phototrophy(17.41%)as the main functions of epiphytic bacteria on leaves of different life form plants.FUNGuild prediction indicated that phyllosphere epiphytic fungi primarily served as Saprotrophs(81.77%),Pathotrophs(17.41%),and Symbiotrophs(0.82%).Co-occurrence network analysis demonstrated a predominance of positive correlations among different microbial taxa.Raup-Crick dissimilarity index analysis revealed that deterministic processes predominantly influenced phyllosphere bacterial and fungal community assembly.Variance partitioning analysis and random forest modeling suggested that plant leaf functional traits significantly impacted both bacterial and fungal community composition,with fungal community composition showing a closer association with leaf nutrients and physiology compared with bacterial community composition.The distinct responses of bacterial and fungal communities to plant traits were attributed to the differing properties of bacteria and fungi,such as bacteria having higher potential dispersal rates and broader ecological niches than fungi.Overall,the results indicate that phyllosphere bacterial and fungal communities undergo similar community assembly processes,with fungi being more influenced by plant characteristics than bacteria.These findings offer novel insights into the ecology of phyllosphere microbial communities of desert plants.

New Bacterial Agents to Limit <i>Colletotrichum gloeosporioides</i>Development on Mango

Mango anthracnose disease forms typical irregular-shaped black necrotic spots on the fruit peel of mature fruit and is caused by Colletotrichum gloeosporioides. In order to improve the disease control with a limited use of fungicides, new microbial agents able to limit the growth of the pathogen were searched in the indigenous natural flora of mango surface. In order to find a suitable biocontrol agent, a screening was applied to 305 epiphytic bacteria isolated from the carposphere of 17 mango cultivars sampled from eight locations on Reunion Island. The screening approach involved a first step based on the ability of the isolates to form a biofilm, to grow under fruit storage conditions, and to interfere with the development of C. gloeosporioides. In a second step, the capability of selected isolates to limit C. gloeosporioides in vitro mycelial growth and conidia germination was assessed and species identified. The most effective bacteria belonged to the Enterobacter, Pantoea, Kosakonia and Leuconostoc genera, but for some of them, their safe use has to be demonstrated. Efficacy in vivo, performed on wounded mature mango fruit, was limited, probably because of the wounding inoculation strategy favoring the pathogen. Future biocontrol treatments should focus on preharvest applications to enhance the protective benefit.

Ecological damage of submerged macrophyte Myriophyllum spicatum by cell extracts from microcystin(MC)-and non-MC-producing cyanobacteria,Microcystis

To explore how decomposed Microcystis-dominant cyanobacterial blooms affect submerged macrophytes,the submerged plant Myriophyllum spicatum was exposed to cell extracts from microcystin(MC)-and non-MC-producing Microcystis strains in a laboratory experiment.Results showed that both Mcracystis cell extracts exerted obvious damages to plant biomass,photosynthesis,primary and secondary metabolism measures,and resistance of plant antioxidant systems,with MC-producing Microcystis having stronger effects due to the presence of MCs.Cyanotoxins other than MCs responsible for the negative effects from both strains needs further identification.The Shannon diversity and Chao1 indices of epiphytic and planktonic bacteria were decreased by the cell extracts from both Microcystis strains.However,epiphytic and planktonic bacterial communities responded differently to cell extracts at the genus level.The dominant genera of planktonic bacteria including Enterobacter,Pseudomonas,and Novosphingobium from phylum Proteobacteria,Chryseobacterium from phylum Bacteroidetes,and Microbacterium from Actinobacteriota in the treatments with cell extracts were previously reported to have strains with algicidal and MC-degrading capabilities.B acterial genes associated with energy production and conversion,amino acid transport and metabolism,and inorganic ion transport and metabolism,were more abundant in both treatments than the control for planktonic bacteria,but less abundant for epiphytic bacteria.We speculate that planktonic bacterial communities have the potential to use and degrade substances derived from Microcystis cell extracts,which may be beneficial for M.spicatum to alleviate damages from Microcystis.Further research is needed to verify the structure and function dynamics of epiphytic and planktonic bacteria in the interaction between cyanobacteria and submerged macrophytes.