Distribution,Activity,and Novel Lineages Of Archaea In The Pearl River Estuary

The Pearl River Estuary(PRE)is a unique place to study the environmental adaptability of marine archaea as it is located in the land-sea interaction zone and greatly affected by human activities.However,the current distribution and activity of marine archaea in the estuary along the gradient of environmental factors have not been systematically studied.This thesis aimed to further understand the influence of salinity and other environmental factors on the composition,distribution,abundance and activity of archaeal communities in the PRE and adjacent Shenzhen Bay.The short-read sequencing of SSU r RNA gene based on primer amplification has been widely used to discover new species of marine microorganisms.However,this method is affected by the preference of primers and the lack of coverage o f sequence information.It is difficult to detect new lineages of microorganisms that cannot be amplified by universal primers.In this study,the RNA with poly(A)tailing sequenced by Pac Bio SMRT sequencing technology is used to develop a method for primer-free full-length ribosomal SSU r RNA gene sequencing.The results showed that this novel approach can discover new microbial species that could not be detected using previous methods.This new method allowed us to detect novel species of MGI archaea(Thaumarchaeota)in the seawater samples in the PRE.By high-throughput sequencing analysis of 16 S r RNA sequences of bacteria and archaea,Alpha diversity and Beta diversity of marine archaea and bacterial communities were calculated and compared.The results s howed that the Alpha diversity of archaea in Shenzhen Bay waters was higher than that in the PRE;the Alpha diversity of archaea in Shenzhen Bay waters and sediments were relatively similar.The Alpha diversity of archaea in the DNA samples of the PRE was higher than that in the RNA samples,indicating that a large part of the archaea cells were non-active in the PRE.There was no significant difference in archaeal community structure between the PRE and the Shenzhen Bay waters(Beta analysis),reflecting that those areas were connected;However,the community structure was significantly different between the waters and sediments in Shenzhen Bay,reflecting the contrasts in physical and chemical conditions of the aquatic and benthic environments.The archaeal communities were mainly composed of MGII and MGI in the PRE and Shenzhen Bay waters,which have higher relative abundance in the polluted environment.This shows that the nitrogen emission pollution related to human activities has a certain impact on the distribution of.In addition,with metagenome sequencing and metatranscriptomics abundance analysis,the distribution of marine archaea II-MGII along the PRE salinity gradient and physiological activity were studied.The MGII transcriptome proportion increased with the increase salinity in the PRE waters,indicated that MGII were more active in the high salinity waters than that in freshwaters.This study added to the understanding of the interactions between planktonic archaea and the environment in the PRE.The primer-free sequencing provides a new technical approach to expand the structural and functional diversities of archaea in the marine ecosystem.