The genus Cylindrotheca consists of a small group of marine diatoms with a few species described. Eleven isolates of diatoms identified as Cylindrotheca closterium morphologically were obtained from Jiaozhou Bay with ...The genus Cylindrotheca consists of a small group of marine diatoms with a few species described. Eleven isolates of diatoms identified as Cylindrotheca closterium morphologically were obtained from Jiaozhou Bay with their nuclear-encoded small-subunit ribosomal RNA （SSU rDNA） and chloroplast-encoded rbcL gene sequences determined in this study. Interestingly, very high sequence divergences of SSU rDNA and rbcL gene were found among these isolates, and numerous nucleotide variation of rbcL gene caused relatively few variation of deduced amino acid sequence. Phylogenetic analyses based on SSU rDNA and rbcL gene, respectively, grouped the isolates into 6 clades. Phylogenetic tree of SSU rDNA placed all the Cylindrotheca isolates together, separating them into two lineages clearly. LineageⅠ was composed of the eleven C. closterium isolates obtained in this study together with another C. closterium isolate, but some clades were not well supported. LineageⅠwas contained two C. closterium isolates and one C. fusiformis isolate. Phylogenetic analysis of rbcL gene also separated the Cylindrotheca isolates into two well-defined lineages. The eleven C. closterium isolates formed a lineage and all clades were supported strongly. Statistical comparisons of SSU rDNA indicated that the average distance within lineageⅠwas significantly higher than that of other microalgae species （P 〈0.01）. These results suggested the existence of cryptic species within C. closterium.展开更多
Giardia duodenalis exhibits seven assemblages (A-G) that are distributed in different hosts. The A and B assemblages are commonly found in humans and several mammals, while C and D assemblages are typically found in d...Giardia duodenalis exhibits seven assemblages (A-G) that are distributed in different hosts. The A and B assemblages are commonly found in humans and several mammals, while C and D assemblages are typically found in dogs. The purpose of this study was to determine the assemblage of Giardia duodenalis present in the stool samples of ten canines using an assay based on PCR amplification, restriction analysis, and sequencing of the small subunit ribosomal DNA (SSU-rDNA), β-giardin, and triosephosphate isomerase (tpi) genes in order to establish the similarities or differences between the assemblage obtained with each gene. The results indicated that all positive isolates belonged to assemblage A, and specifically to the sub-assemblage A-I. A comparison of the SSU-rDNA gene sequence revealed the presence of three subgroups of assemblage A. These findings highlight the importance of canine transmission of Giardia in Mexico and its genetic plasticity. They also establish a method for additional and more molecularly extensive epidemiological studies to improve sanitation and hygiene in the most affected areas.展开更多
Dinoflagellates are unicellular eukaryotic protists that dominate in all coastal waters, and are also present in oceanic waters. Despite the central importance of dinoflagellates in global primary production, the rela...Dinoflagellates are unicellular eukaryotic protists that dominate in all coastal waters, and are also present in oceanic waters. Despite the central importance of dinoflagellates in global primary production, the relationship between dinoflagellates and bacteria are still poorly understood. In order to understand the ecological interaction between bacterial and dinoflagellates communities, denaturing gradient gel electrophoresis (DGGE) and SSU rRNA sequencing were applied to monitoring the population dynamics of bacteria and dinoflagellates from the onset to disappearance of a dinoflagellates bloom occurred in Baltimore Inner Harbor, from April 15 to 24,2002. Although Prorocentrum minimum was the major bloom forming species under the light microscopy, DGGE method with dinoflagellate specific primers demonstrated that Prorocentrum micans, Gymnodinium galatheanum and Gyrodinium uncatenum were also present during the bloom. Population shifts among the minor dinoflagellate groups were observed. DGGE of PCR-amplified 16S rRNA gene fragments indicated that cyanobacteria, α, β, γ-proteobacteria, Flavobacterium Bacteroides-Cytophaga (FBC), and Planctomcetes were the major components of bacterial assemblages during the bloom. DGGE analysis showed that Cytophagales and α-proteobacteria played important roles at different stages of dinoflagellates bloom. DGGE can be used as a rapid tool to simultaneously monitor population dynamics of both bacterial and dinoflagellates communities in aquatic environments, which is demonstrated here.展开更多
基金This research was financially supported by an open project of The Key Laboratory of Mariculture of The Ministry of Education of China affiliated to 0cean umversity of China(200405)by the National Natural Science Foundation of China(30471318,40176028).
文摘The genus Cylindrotheca consists of a small group of marine diatoms with a few species described. Eleven isolates of diatoms identified as Cylindrotheca closterium morphologically were obtained from Jiaozhou Bay with their nuclear-encoded small-subunit ribosomal RNA （SSU rDNA） and chloroplast-encoded rbcL gene sequences determined in this study. Interestingly, very high sequence divergences of SSU rDNA and rbcL gene were found among these isolates, and numerous nucleotide variation of rbcL gene caused relatively few variation of deduced amino acid sequence. Phylogenetic analyses based on SSU rDNA and rbcL gene, respectively, grouped the isolates into 6 clades. Phylogenetic tree of SSU rDNA placed all the Cylindrotheca isolates together, separating them into two lineages clearly. LineageⅠ was composed of the eleven C. closterium isolates obtained in this study together with another C. closterium isolate, but some clades were not well supported. LineageⅠwas contained two C. closterium isolates and one C. fusiformis isolate. Phylogenetic analysis of rbcL gene also separated the Cylindrotheca isolates into two well-defined lineages. The eleven C. closterium isolates formed a lineage and all clades were supported strongly. Statistical comparisons of SSU rDNA indicated that the average distance within lineageⅠwas significantly higher than that of other microalgae species （P 〈0.01）. These results suggested the existence of cryptic species within C. closterium.
文摘Giardia duodenalis exhibits seven assemblages (A-G) that are distributed in different hosts. The A and B assemblages are commonly found in humans and several mammals, while C and D assemblages are typically found in dogs. The purpose of this study was to determine the assemblage of Giardia duodenalis present in the stool samples of ten canines using an assay based on PCR amplification, restriction analysis, and sequencing of the small subunit ribosomal DNA (SSU-rDNA), β-giardin, and triosephosphate isomerase (tpi) genes in order to establish the similarities or differences between the assemblage obtained with each gene. The results indicated that all positive isolates belonged to assemblage A, and specifically to the sub-assemblage A-I. A comparison of the SSU-rDNA gene sequence revealed the presence of three subgroups of assemblage A. These findings highlight the importance of canine transmission of Giardia in Mexico and its genetic plasticity. They also establish a method for additional and more molecularly extensive epidemiological studies to improve sanitation and hygiene in the most affected areas.
文摘Dinoflagellates are unicellular eukaryotic protists that dominate in all coastal waters, and are also present in oceanic waters. Despite the central importance of dinoflagellates in global primary production, the relationship between dinoflagellates and bacteria are still poorly understood. In order to understand the ecological interaction between bacterial and dinoflagellates communities, denaturing gradient gel electrophoresis (DGGE) and SSU rRNA sequencing were applied to monitoring the population dynamics of bacteria and dinoflagellates from the onset to disappearance of a dinoflagellates bloom occurred in Baltimore Inner Harbor, from April 15 to 24,2002. Although Prorocentrum minimum was the major bloom forming species under the light microscopy, DGGE method with dinoflagellate specific primers demonstrated that Prorocentrum micans, Gymnodinium galatheanum and Gyrodinium uncatenum were also present during the bloom. Population shifts among the minor dinoflagellate groups were observed. DGGE of PCR-amplified 16S rRNA gene fragments indicated that cyanobacteria, α, β, γ-proteobacteria, Flavobacterium Bacteroides-Cytophaga (FBC), and Planctomcetes were the major components of bacterial assemblages during the bloom. DGGE analysis showed that Cytophagales and α-proteobacteria played important roles at different stages of dinoflagellates bloom. DGGE can be used as a rapid tool to simultaneously monitor population dynamics of both bacterial and dinoflagellates communities in aquatic environments, which is demonstrated here.
基金Supported by the National Natural Science Foundation of China(31501845,31672280,31970409)Chongqing Natural Science Foundation(cstc2017jcyjAX0165 and cstc2018jcyjAX0738)+1 种基金Venture&Innovation Support Program for Chongqing Overseas Returnees(cx2018108)Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN201900505)。
