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1.
A phosphotransferase-dependent aryl-β-glucoside uptake and utilisation system (abg) was isolated from the ruminal Clostridium (“C. longisporum”). The system is composed of three genes, abgG, abgF and abgA, and a number of regulatory regions, including terminator/antiterminator type stem-loop structures preceding the abgG and abgF genes. Similarity analysis of the proteins encoded by these genes indicated that they were responsible for the regulation of the abg system through antitermination (AbgG), the uptake and phosphorylation of aryl-β-glucosides (AbgF) and the hydrolysis of the intracellular phosphorylated glycosides (AbgA). Experimental evidence for the functions of AbgF and AbgA was obtained. Although it was not possible to demonstrate any function for AbgG, a promoter 5′ to the abgG gene was identified which was responsible for expression of the downstream genes. The abg system is remarkably similar to operons from the gram negative Enterobacteriaceae, both in the coding and non-coding regulatory regions. Received: 3 April 1997 / Accepted: 8 September 1997  相似文献   

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The problems of delimitation of species of Prosopis originate from the few morphological discontinuities which exist among some of them; some, however, originated as a result of wide distribution of germplasm without proper knowledge of the species, in particular, much material catalogued as P. juliflora, but being of other species, was distributed for reforestation projects worldwide. This work tests the morphological results obtained for P. pallida and P. limensis of the Peruvian–Ecuadorian coast and for P. juliflora of the Caribbean Basin of Colombia and Venezuela utilizing a study of AFLPs and a study of the morphology of plantlets developed in a conventional garden study. The phenogram obtained for the AFLPs demonstrates each of the three species to be a well differentiated cluster and the molecular variance between them is significantly greater than the variance within each species. Study of the plantlets also indicates statistically significant differences for four morphological characters between P. juliflora and the other two species (P. pallida and P. limensis). These results, in addition to the morphological differentiation evident between adult plants of P. pallida and P. limensis and the clear separation of these two species from P. juliflora, corroborate the genetic identity of the three taxa analyzed.  相似文献   

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This study reviews the nominal taxa within the species “Nemachilus” stoliczkae and “N.” dorsonotatus, described by Herzenstein (1888). N. dorsonotatus, N. d. retropinnis, and N. plagiognathus are reviewed within the species Triplophysa stoliczkae; it is suggested that this species is represented by at least 5 subspecies. N. stoliczkae brevicauda, N. s. leptosoma (synonym, N. s. productus), and N. s. crassicauda are considered as valid species, the last 2 are related to the group including the species T. tenuis, T. choprai, T. tenuicauda, and T. yasinensis rather than with T. stoliczkae. It was shown that the “stoliczkae” species group (sensu Prokofiev, 2001) should be divided into three species groups: “stoliczkae” (s. str.), “tenuis,” and “robusta”; their diagnoses and the species composition are presented. A new species from the “stoliczkae” group is described (T. scapanognatha sp. nova), related to T. tanggulaensis (Zhu, 1982). Original Russian Text ? A.M. Prokofiev, 2007, published in Voprosy Ikhtiologii, 2007, Vol. 47, No. 1, pp. 5–25.  相似文献   

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Summary The ultrastructure of the secondary lamellae has been examined in four species of free-swimming elasmobranchs, two species of Raia and five species of bony flatfishes. Microvilli which are present on the outer epithelial surface vary in form and size. It is suggested that a possible function of the microvilli is to anchor a surface mucus covering whose possible functions are discussed. Vesicles are found immediately beneath the microvilli in elasmobranchs but not in teleosts. Chloride and mucous cells are present on the secondary lamellae of all species and often have microvilli of greater length than on the other cells of the epithelium. Micropinocytotic vesicles are found on both sides of the basement membrane. The number of columns enclosed in the pillar cells varied from 5–11.The water-blood pathway showed variations in thickness not only between different species but also in different parts of individual secondary lamellae. A general trend in the mean total thickness was found, being greater in the swimming elasmobranchs (10.22 ) than in the rays (5.47 ) and bony flatfish (3.59 ). This trend is also seen in the greater length of microvilli and thickness of basement membrane in the elasmobranchs than in the teleosts.  相似文献   

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J Li  GD Ren 《ZooKeys》2012,(203):47-53
Two new species Episcapha (Ephicaspa) lushuiensissp. n. and Episcapha (Ephicaspa) quadriconcavasp. n. are described and illustrated from China. A key to known species of subgenus Ephicaspa is provided. A map of the collecting sites is given.  相似文献   

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Summary Salivary gland cells of members of theDrosophila melanogaster group (from four different subgroups) were examined electron microscopically and histochemically during the late larval period of development. The secretory product, which is supposed to be utilized as glue at the time of puparium formation, appears, by analogy to Palade and Jamieson's results, to be synthesized partially in the rough endoplasmic reticulum (RER) and partially in the Golgi complex. The latter is also the usual site of the packaging of the product into secretory granules, except in the case of one of the secretory granule components ofD. lucipennis. The phylogenetic relationships among the subgroups, implied by the morphological appearance of the secretory granules, fit well with the existing phylogenetic relationships within the group. The secretory granules of each species have their own morphological features; granules of species of the same subgroup share some of these features. Secretion occurs from the cells via exocytosis during which the morphology of the secretory granules changes. Light microscope examination of PAS (Periodic Acid-Schiff reaction) stained glands shows a strong positive reaction in most species, with the exception of the species of thesuzukii subgroup which show a weak, or a negative reaction (D. rajasekari). Electron histochemical localization of polysaccharides in the secretory granules was possible inD. melanogaster and the species of theananassae subgroup.  相似文献   

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Chromosome mapping of three common markers, ie major and 5S rRNA genes (rDNA) and telomeric repeats, and conventional chromosome bandings were applied to two sibling species, Apodemus sylvaticus Linnaeus, 1758 and A. flavicollis Melchior, 1834, to further investigate intra- and interspecific karyological differentiation in the genus Apodemus. A slight variation of the rDNA-patterns was detected between the two Apodemus species. In both of them, the major NORs were located on autosome pairs 8, 11, 12 and 22, while the two other rDNA sites detected on chromosomes 7 and 21 were variable in, respectively, A. sylvaticus and A. flavicollis. Several tiny rDNA sites were present on the sex chromosomes in both species, but their incidence was lower in A. flavicollis. Single 5S rDNA chromosomal sites were conserved on chromosome pair 20. No interstitial sites of telomeric repeats were present in either species. In the Sicilian population of A. sylvaticus, the constitutive heterochromatin pattern corresponded to the “sylvaticus-E1” cytotype, while A. flavicollis had a species-specific pattern restricted to centromeres of all chromosomes. The results are discussed in relation to cytogenetic data available for the genus, with emphasis on the Sylvaemus group/subgenus.  相似文献   

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The newly defined Agrilus beatissimus species–group comprising seven species from Southeast Asia is revised. The key to species is provided and complemented with illustrations of habitus, genitalia and type specimens. The following five new species are described: Agrilus bilyanus sp. nov. (Thailand); A. campana sp. nov. (Laos); A. galazopos sp. nov. (Laos); A. plurifrons sp. nov. (Laos, Myanmar) and A. undatus sp. nov. (Laos). Comprehensive commented references, data on type specimens and new faunal records are cited. The distribution is updated for A. beatissimusDescarpentries and Villiers 1963 and A. dunoyeriBaudon 1968.  相似文献   

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The Research Institute for Nature and Forest (INBO) has been performing standardized fish stock assessments in Flanders, Belgium. This Flemish Fish Monitoring Network aims to assess fish populations in public waters at regular time intervals in both inland waters and estuaries. This monitoring was set up in support of the Water Framework Directive, the Habitat Directive, the Eel Regulation, the Red List of fishes, fish stock management, biodiversity research, and to assess the colonization and spreading of non-native fish species. The collected data are consolidated in the Fish Information System or VIS. From VIS, the occurrence data are now published at the INBO IPT as two datasets: ‘VIS - Fishes in inland waters in Flanders, Belgium’ and ‘VIS - Fishes in estuarine waters in Flanders, Belgium’. Together these datasets represent a complete overview of the distribution and abundance of fish species pertaining in Flanders from late 1992 to the end of 2012. This data paper discusses both datasets together, as both have a similar methodology and structure. The inland waters dataset contains over 350,000 fish observations, sampled between 1992 and 2012 from over 2,000 locations in inland rivers, streams, canals, and enclosed waters in Flanders. The dataset includes 64 fish species, as well as a number of non-target species (mainly crustaceans). The estuarine waters dataset contains over 44,000 fish observations, sampled between 1995 and 2012 from almost 50 locations in the estuaries of the rivers Yser and Scheldt (“Zeeschelde”), including two sampling sites in the Netherlands. The dataset includes 69 fish species and a number of non-target crustacean species. To foster broad and collaborative use, the data are dedicated to the public domain under a Creative Commons Zero waiver and reference the INBO norms for data use.  相似文献   

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The method of polymerase chain reaction with random primers (RAPD PCR) was used to identify the progeny of the crosses between three sturgeon species, Amur sturgeon (Acipenser schrenckii Brandt, 1869), Siberian sturgeon (A. baerii Brandt, 1869), and sterlet (A. ruthenus Linnaeus, 1758). Using ten primers, genetic variation in 70 yearlings, produced in seven individual crosses: Acipenser schrenckii × A. schrenckii, A. baerii × A. baerii, A. ruthenus × A. ruthenus, A. schrenckii × A. baerii, A. baerii × A. schrenckii, A. schrenckii × A. ruthenus, and A. ruthenus × A. schrenckii was described and evaluated. It was demonstrated that the samples composed of hybrids from individual crosses were more variable than the samples of parental species. On the other hand, pooled samples of hybrids from two cross directions were genetically less variable than the pooled samples of their parents. The three main features of the hybrid RAPD profiles identified included: (1) preservation of marker DNA fragments of both parents in one genome; (2) presence of specific DNA fragments, absent from both parents; and (3) dependence of the frequency of some DNA fragments from the cross direction. Multidimensional scaling clearly distinguishes in the space of three coordinates the individuals of original species and the hybrid progeny with differentiation in the groups of direct and backcross hybrids. Analysis of relationships (UPGMA and NJ) pointed to substantial differentiation between the species, as well as between the species and hybrid progeny. Close genetic relationships between direct and backcross hybrids were demonstrated. Multilocus RAPD markers in association with statistical methods are considered to be the useful tool for discrimination of interspecific hybrids of sturgeon. Possible reasons for the differences in the hybrid RAPD profiles are discussed. Original Russian Text ? K.V. Rozhkovan, G.N. Chelomina, E.I. Rachek, 2008, published in Genetika, 2008, Vol. 44, No. 11, pp. 1453–1460.  相似文献   

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In this essay, three currently hotly debated issues in biological systematics, i.e., the paraphyletic group, the PhyloCode, and the phylogenetic species concept, have been briefly reviewed. (1) It is widely acknowledged that cladistics has made some positive contributions to the study of systematics. In particular, the employment of outgroup analysis for assessing character polarities, the application of synapomorphies to the inference of relationships between taxa, and the use of cladistic methods for reconstructing phylogeny, have all greatly facilitated the improvement of systematic approaches. A fatal flaw in cladistics is its refusal to accept paraphyletic groups. Frankly, we are adherents and practitioners of phyletics, and hence consider paraphyletic groups to be acceptable. For example, an AFLP analysis has shown that Zabelia (Caprifoliaceae) can be included in Abelia, but the members in Zabelia differ from those in Abelia not only in pollen morphology, but also in having persistent petioles dilated and connate at base, thus enclosing axillary buds, characters of adaptive significance obtained possibly when Zabelia members entered a new ecological niche, so we consider that they are better treated as two independent genera, though indeed such a treatment makes Abelia paraphyletic. (2) Some cladists pointed out that as the tool for communication and the system for information storage and retrieval, biological nomenclature is required to be unambiguous, unique and stable. They criticise the Linnaean rank-based system of nomenclature for failing to satisfy such requirements for the naming of clades and species. To address this problem, the PhyloCode is proposed in recent years, in which three definitions for clade naming are given, i.e., the node-based, the stem-based, and the apomorphy-based. We are of the opinion that since the Linnaean binominal system of botanical nomenclature has existed for nearly 250 years, the rejection of this system and the adoption of the PhyloCode would create a state of chaos in botanical nomenclature. This does not mean that there exist no merits in the proposals made by the PhyloCode supporters. We suggest that further studies should be conducted for its practical application. (3) It has been well known that there are many problems with the application of the biological species concept in plants, and thus at the present time the majority of plant systematists actually seldom use this concept in their practical work. The rapid development of cladistic approach has motivated the proposal of the phylogenetic species concept. This species concept is established based on three criteria, i.e., the autamorphy, the diagnosability and the basal exclusivity, hence the autamorphy species concept, the diagnosability species concept, and the genealogical concept are created respectively. Nevertheless, the morpho-geographical species concept is still predominantly adopted in plant systematics. When using this species concept, however, we should also take into account the data from other sources, particularly those from pollination biology, breeding system and molecular systematics.  相似文献   

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Thirty-two specimens of 11 freshwater fish species from Lake Biwa, Japan were surveyed for coccidian infections. Four fish species proved to be infected with apicomplexans belonging to the genus Goussia. Altogether, seven Goussia species were found. Oöcysts of four species inhabiting the intestinal epithelium were shed at the sporulated stage. Two other intestinal species left the fish unsporulated. A few relatively large and aged oöcysts of a further species were found in the renal tubules. The sporulated intestinal species were described as Goussia biwaensis n. sp., G. grygieri n. sp., G. nipponica n. sp. and G. wakabayashii n. sp.  相似文献   

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The genus Cistus is a widespread family growing around the Mediterranean area. There is a unique natural population of C. heterophyllus subsp. carthaginensis in Europe (Murcia, Spain) containing 22 individuals. Morphology of these plants suggests the co-occurrence of two distinct types within the population. One type would resemble C. heterophyllus, and a second type would be the result of hybridization events between this endangered population and the locally abundant Cistus albidus. These hybrids have been described in Africa as C. × clausonis. We have analyzed sequences of the chloroplast genes trnK-matK, rbcL, rpoB, rpoC1 and two intergenic regions, trnL-F and trnH-psbA. Surprisingly, we observed heteroplasmy for rpoB and rpoC1 genes in C. heterophyllus and the local C. × clausonis, but not in C. albidus or C. monspeliensis. We found two distinct alleles of rpoB, one present in all species and a second present only in C. heterophyllus and the local C. × clausonis. We also detected two alleles of rpoC1, one common to all species analyzed and a second present only in the local C. × clausonis. Our results show that there is a distinctive rpoB allele common to C. heterophyllus and C. × clausonis from Africa and Europe. The unique rpoC1 allele found in the local C. × clausonis indicates a different origin of this small population, indicating it is not a hybrid formed with the C. albidus or C. heterophyllus currently present in this location.  相似文献   

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