| Ticks,as obligate blood-sucking surface parasitic arthropods,are widely distributed all over the world.They have a wide host range and transmit a great variety of pathogens that have a significant adverse effect on the health of humans and animals.In addition to pathogens,ticks will also acquire abundant microorganisms from the natural environment and the host’s blood.These microorganisms not only have a stable community structure in the host,but also establish a complex interspecies ecological relationship during long-term coevolution with the host.Argas japonicus belongs to Argasidae,Argas and mainly parasitizes on the body surface of birds.It is reported that A.japonicus only distributes in Beijing,Jilin Province and Liaoning Province in China.In June 2016,our research team firstly discovered A.japonicus in the Inner Mongolia Autonomous Region.A large population of A.japonicus appeared in local residents,sucking blood and causing inflammation in the skin,which seriously affected the health and daily life of the local residents.In this study,the 16 S rRNA gene of the nymphs and adults were sequenced and analyzed by high-throughput sequencing technology,the microbial community information of A.japonicus was investigated.The results showed that the composition of microbial community in A.japonicus was rich,and the relationship of microbial diversity in the tick was as follows: males>nymphs>females.A total of 8 phyla were present at the phylum level,Proteobacteria represented the phylum with the most abundant,followed by Firmicutes and Actinobacteria.At the genus level,a total of 107 genera were observed.Staphylococcus had the most abundance,followed by Alcaligenes and Rickettsia.Phylogenetic analysis of Rickettsia based on the 16 S rRNA gene showed that the R.limoae and a novel Rickettsia in A.japonicus,which was named R-Aj(Rickettsia of A.japonicus).The 16 S rRNA gene clone libraries of A.japonicus was constructed and analyzed by restriction fragment length polymorphism.The results showed that the bacteria were Alcaligenes,Rickettsia,Staphylococcus and Pseudomonas contained in both males and females.However,Bacillus,Klebsiella and Yersinia were also detected in males,so the diversity of males was more abundant than females.Sequence alignment results showed that the 16 S rRNA gene sequence of Rickettsia selected from the gene clone libraries was consistent with the sequence of R-Aj in the high-throughput sequencing results.However R.limoae was not detected from the gene clone libraries.The R-Aj in A.japonicus was detected and identified by diagnostic PCR and multilocus sequence analysis.The results showed that the infection rate of R-Aj in males was 80%,and the infection rate in females was 56.67%.Based on gltA,ompA and omp B genes of R-Aj,a single and multiple gene phylogenetic tree was constructed by multilocus sequence analysis.It was preliminarily confirmed that R-Aj was a novel Rickettsia and had potential pathogenicity. |
