After deregulating the purine and riboflavin synthesis in the Gram-positive bacterium Bacillus subtilis,it is critical to amplify riboflavin operon with appropriate dosage in the host strain for remarkable increase of...After deregulating the purine and riboflavin synthesis in the Gram-positive bacterium Bacillus subtilis,it is critical to amplify riboflavin operon with appropriate dosage in the host strain for remarkable increase of riboflavin production.Bacillus subtilis RH13, a riboflavin-producing strain, was selected as host strain in the construction of engineering strains by protoplast fusion. The integrative plasmid pRB63 and autonomous plasmid pRB49, pRB62 containing riboflavin operon of B.subtilis 24 were constructed and transformed into the host strain respectively. Increasing one operon copy in B.subtilis RH13 results in about 0.4 g/L improvement in riboflavin yield and the appropriate number of operon copies was about 7—8. Amplifying more riboflavin operons is of no use for further improvement of yield of riboflavin. Furthermore, excessive operon dosage results in metabolic unbalance and is fatal to the host cells producing riboflavin.展开更多
In this paper, we explore possible conflict between morphological and molecular interpretations of phylogenetic relationships within the well-known peritrichous genus Zoothamnium. On the basis of morphological evidenc...In this paper, we explore possible conflict between morphological and molecular interpretations of phylogenetic relationships within the well-known peritrichous genus Zoothamnium. On the basis of morphological evidence, for a long time this genus has been believed to be a well-defined monophyletic taxon. Nonetheless, Zoothamnium exhibits higher genetic diversity than the gross morphology of its species. Here, we used all available genetic information for the small subunit of ribosomal RNA （SSU rRNA） and internal transcribed spacer region （ITS1-5.8S-ITS2） for this genus to reconstruct phylogenies for four datasets （SSU rRNA, ITS1, ITS2, and ITS1-5.8S-ITS2） and a combined dataset （SSU rRNA＋ITSI-5.8S- ITS2） using different phylogenetic methods and with consideration of the secondary structure of the genes. Confidence in phylogenetic tree selection was assessed with the approximately unbiased test. The molecular results showed both that Zoothamnium is more likely to be polyphyletic, and morphologically similar genera Zoothamnopsis and Myoschiston were always nested among Zoothamnium species. Accordingly, as with some other groups of ciliates, to understand more fully the correct phylogeny of Zoothamnium there remains a need for additional data from both morphological and molecular studies, covering additional Zoothamnium spp. and members of closely related genera （e.g. Zoothamnopsis, Myoschiston, and Epistylis）.展开更多
Distant hybridization refers to crosses between two different species or higher-ranking taxa that enables interspecific genome transfer and leads to changes in phenotypes and genotypes of the resulting progeny.If prog...Distant hybridization refers to crosses between two different species or higher-ranking taxa that enables interspecific genome transfer and leads to changes in phenotypes and genotypes of the resulting progeny.If progeny derived from distant hybridization are bisexual and fertile,they can form a hybrid lineage through self-mating,with major implications for evolutionary biology,genetics,and breeding.Here,we review and summarize the published literature,and present our results on fish distant hybridization.Relevant problems involving distant hybridization between orders,families,subfamilies,genera,and species of animals are introduced and discussed,with an additional focus on fish distant hybrid lineages,genetic variation,patterns,and applications.Our review serves as a useful reference for evolutionary biology research and animal genetic breeding.展开更多
文摘After deregulating the purine and riboflavin synthesis in the Gram-positive bacterium Bacillus subtilis,it is critical to amplify riboflavin operon with appropriate dosage in the host strain for remarkable increase of riboflavin production.Bacillus subtilis RH13, a riboflavin-producing strain, was selected as host strain in the construction of engineering strains by protoplast fusion. The integrative plasmid pRB63 and autonomous plasmid pRB49, pRB62 containing riboflavin operon of B.subtilis 24 were constructed and transformed into the host strain respectively. Increasing one operon copy in B.subtilis RH13 results in about 0.4 g/L improvement in riboflavin yield and the appropriate number of operon copies was about 7—8. Amplifying more riboflavin operons is of no use for further improvement of yield of riboflavin. Furthermore, excessive operon dosage results in metabolic unbalance and is fatal to the host cells producing riboflavin.
基金Supported by the National Natural Science Foundation of China(Nos.31071898,31111120437)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China+1 种基金the Key Laboratory of Mariculture(KLM),Ministry of Education,Ocean University of China,the Research Group Project(No.RGP-VPP-083)the King Saud University Deanship of Scientific Research
文摘In this paper, we explore possible conflict between morphological and molecular interpretations of phylogenetic relationships within the well-known peritrichous genus Zoothamnium. On the basis of morphological evidence, for a long time this genus has been believed to be a well-defined monophyletic taxon. Nonetheless, Zoothamnium exhibits higher genetic diversity than the gross morphology of its species. Here, we used all available genetic information for the small subunit of ribosomal RNA （SSU rRNA） and internal transcribed spacer region （ITS1-5.8S-ITS2） for this genus to reconstruct phylogenies for four datasets （SSU rRNA, ITS1, ITS2, and ITS1-5.8S-ITS2） and a combined dataset （SSU rRNA＋ITSI-5.8S- ITS2） using different phylogenetic methods and with consideration of the secondary structure of the genes. Confidence in phylogenetic tree selection was assessed with the approximately unbiased test. The molecular results showed both that Zoothamnium is more likely to be polyphyletic, and morphologically similar genera Zoothamnopsis and Myoschiston were always nested among Zoothamnium species. Accordingly, as with some other groups of ciliates, to understand more fully the correct phylogeny of Zoothamnium there remains a need for additional data from both morphological and molecular studies, covering additional Zoothamnium spp. and members of closely related genera （e.g. Zoothamnopsis, Myoschiston, and Epistylis）.
基金supported by the Major International Cooperation Projects of the National Natural Science Foundation of China(31210103918)Training Program of the Major Research Plan of the National Natural Science Foundation of China(91331105)+3 种基金the National Key Basic Research Program of China(2012CB722305)the National High Technology Research and Development Program of China(2011AA100403)the Cooperative Innovation Center of Engineering and New Products for Developmental Biology of Hunan Province(20134486)the Construct Program of the Key Discipline in Hunan Province and China
文摘Distant hybridization refers to crosses between two different species or higher-ranking taxa that enables interspecific genome transfer and leads to changes in phenotypes and genotypes of the resulting progeny.If progeny derived from distant hybridization are bisexual and fertile,they can form a hybrid lineage through self-mating,with major implications for evolutionary biology,genetics,and breeding.Here,we review and summarize the published literature,and present our results on fish distant hybridization.Relevant problems involving distant hybridization between orders,families,subfamilies,genera,and species of animals are introduced and discussed,with an additional focus on fish distant hybrid lineages,genetic variation,patterns,and applications.Our review serves as a useful reference for evolutionary biology research and animal genetic breeding.
