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.

不同孔型的Q690高强钢电弧热喷铝表面的抗滑移试验研究

建筑结构采用高强钢能有效减少结构用钢量和安装成本,从而降低建筑结构的碳排放,有利于推动建筑业的高质量发展。高强螺栓摩擦型连接是钢结构中最常用的连接方式之一,其依靠连接板件之间的摩擦力传递荷载,具有刚度高、抗疲劳和抗往复荷载等优点,因此桥梁结构中常常采用此类连接方式。实际工程中,高强螺栓摩擦型连接面临着防腐处理和现场施工装配精度不高的问题。在高强螺栓摩擦型连接表面采用电弧热喷铝喷涂和扩孔的方法可以解决上述问题,因此高强钢的高强螺栓摩擦型连接表面电弧热喷铝和扩孔后的抗滑移性能对该连接的承载能力具有至关重要的影响。为研究不同孔型的Q690高强钢电弧热喷铝表面高强螺栓摩擦型连接抗滑移性能,进行了抗滑移试验与预紧力损失试验。试验考虑了表面喷砂与喷砂后电弧热喷铝两种处理方式,其中电弧热喷铝试验包括了标准孔、大圆孔、长向平行荷载的长槽孔和长向垂直荷载的长槽孔四种不同孔型,而喷砂对照组试验仅包含标准孔。试件在达到滑移荷载时发生破坏并伴随显著的滑移,喷砂表面抗滑移试件的破坏形式为孔周磨损,电弧热喷铝表面抗滑移试件的破坏形式为孔周涂层磨损和剥离。试验结果表明:Q690高强钢喷砂表面抗滑移系数可取0.50,电弧热喷铝表面可取0.60,电弧热喷铝表面具有良好的抗滑移性能,承载力高、性能稳定;电弧热喷铝各孔型试件100 h预紧力损失量为1.9%~2.9%;电弧热喷铝表面的大圆孔、长向平行荷载和长向垂直荷载长槽孔的孔型系数平均值分别为0.98、0.89和0.82,最小值为0.93、0.83和0.77,均大于现行规范取值,规范计算结果偏于安全。