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ALAIN THIÉRY NICOLAS RABET GABRIEL NÈVE 《Biological journal of the Linnean Society. Linnean Society of London》2007,90(1):55-60
The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60. 相似文献
4.
Immunological identification and distribution of dissimilatory heme cd1 and nonheme copper nitrite reductases in denitrifying bacteria 总被引:4,自引:0,他引:4
M S Coyne A Arunakumari B A Averill J M Tiedje 《Applied and environmental microbiology》1989,55(11):2924-2931
Polyclonal antibodies were used to identify heme or copper nitrite reductases in the following groups: 23 taxonomically diverse denitrifiers from culture collections, 100 numerically dominant denitrifiers from geographically diverse environments, and 51 denitrifiers from a culture collection not selected for denitrification. Antisera were raised against heme nitrite reductases from Pseudomonas aeruginosa and Pseudomonas stutzeri and against copper nitrite reductase from Achromobacter cycloclastes. Nitrite reductases were identified by Western immunoblot. Diethyldithiocarbamate, which specifically inhibits copper nitrite reductases, was used to confirm the immunological characterization and determine which type was present in strains nonreactive with any antiserum. For groups in which the type of nitrite reductase has not been previously described, we found that Alcaligenes eutrophus, Bacillus azotoformans, Bradyrhizobium japonicum, Corynebacterium nephridii, and Rhizobium spp. contained copper nitrite reductase, while Aquaspirillum itersonii, Flavobacterium spp., and Pseudomonas fluorescens contained heme nitrite reductase. Heme nitrite reductases dominated, regardless of soil type or geographic origin. They occurred in 64 and 92%, respectively, of denitrifiers in the numerically dominant and nonselected collections. The two nitrite reductase types were mutually exclusive in individual bacteria, but both appeared in different strains from the Alcaligenes and Pseudomonas genera. The heme type predominated in Pseudomonas strains. The heme-type nitrite reductase appeared more conserved if judged by similarities in molecular weights and immunological reactions. The Cu type was found in more taxonomically unrelated strains and varied in molecular weight and antiserum recognition. 相似文献
5.
Amos Banin Glenn C. Carle Sherwood Chang Lelia M. Coyne James B. Orenberg Thomas W. Scattergood 《Origins of life and evolution of the biosphere》1988,18(3):239-265
Two major questions have been raised by prior explorations of Mars. Has there ever been abundant water on Mars? Why is the iron found in the Martian soil not readily seen in the reflectance spectra of the surface? The work reported here describes a model soil system of Mars Soil Analog Materials, MarSAM, with attributes which could help resolve both of these dilemmas. The first set of MarSAM consisted of a suite of variably iron/calcium-exchanged montmorillonite clays. Several properties, including chemical composition, surface-ion composition, water adsorption isotherms, and reflectance spectra, of these clays have been examined. Also, simulations of the Viking Labeled Release Experiment using the MarSAM were performed. The results of these studies show that surface iron and adsorbed water are important determinants of clay behavior as evidenced by changes in reflectance, water absorption, and clay surface reactions. Thus, these materials provide a model soil system which reasonably satisfies the constraints imposed by the Viking analyses and remote spectral observations of the Martian surface, and which offers a sink for significant amounts of water. Finally, our initial results may provide insights into the mechanisms of reactions that occur on clay surfaces as well as a more specific approach to determining the mineralogy of Martian soils. 相似文献
6.
Evolutionary Conservation of Sequences Directing Chromosome Breakage and Rdna Palindrome Formation in Tetrahymenine Ciliates 总被引:2,自引:0,他引:2
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Extensive, programmed chromosome breakage occurs during formation of the somatic macronucleus of ciliated protozoa. The cis-acting signal directing breakage has been most rigorously defined in Tetrahymena thermophila, where it consists of a 15-bp DNA sequence known as Cbs, for chromosome breakage sequence. We have identified sequences identical or nearly identical to the T. thermophila Cbs at sites of breakage flanking the germline micronuclear rDNA locus of six additional species of Tetrahymena as well as members of two related genera. Other general features of the breakage site are also conserved, but surprisingly, the orientation and number of copies of Cbs are not always conserved, suggesting the occurrence of germline rearrangement events over evolutionary time. At one end of the T. thermophila micronuclear rDNA locus, a pair of short inverted repeats adjacent to Cbs directs the formation of a giant palindromic molecule. We have examined the corresponding sequences from two other Tetrahymena species. We find the sequence to be partially conserved, as previously implied from analysis of macronuclear rDNA, but of variable length and organization. 相似文献
7.
Increased biomass production in terrestrial ecosystems with elevated atmospheric CO2 may be constrained by nutrient limitations as a result of increased requirement or reduced availability caused by reduced
turnover rates of nutrients. To determine the short-term impact of nitrogen (N) fertilization on plant biomass production
under elevated CO2, we compared the response of N-fertilized tallgrass prairie at ambient and twice-ambient CO2 levels over a 2-year period. Native tallgrass prairie plots (4.5 m diameter) were exposed continuously (24 h) to ambient
and twice-ambient CO2 from 1 April to 26 October. We compared our results to an unfertilized companion experiment on the same research site. Above-
and belowground biomass production and leaf area of fertilized plots were greater with elevated than ambient CO2 in both years. The increase in biomass at high CO2 occurred mainly aboveground in 1991, a dry year, and belowground in 1990, a wet year. Nitrogen concentration was lower in
plants exposed to elevated CO2, but total standing crop N was greater at high CO2. Increased root biomass under elevated CO2 apparently increased N uptake. The biomass production response to elevated CO2 was much greater on N-fertilized than unfertilized prairie, particularly in the dry year. We conclude that biomass production
response to elevated CO2 was suppressed by N limitation in years with below-normal precipitation. Reduced N concentration in above- and belowground
biomass could slow microbial degradation of soil organic matter and surface litter, thereby exacerbating N limitation in the
long term. 相似文献
8.
David J. Evans Gerald B. Pier Michael J. Coyne Jr Joanna B. Goldberg 《Molecular microbiology》1994,13(3):427-434
Summary
Strains of Pseudomonas aeruginosa initially isolated from patients with cystic fibrosis (CF) often express a smooth lipopolysaccharide (LPS) containing many long O side-chain antigens, but once a chronic infection is established, strains recovered from these patients express little or no LPS O antigen. The genetic basis for this loss of O antigen expression by P. aeruginosa CF isolates is unknown. We report here that 20 CF isoiates of P. aeruginosa , 13 of which are LPS-rough, were each capable of expressing serogroup 011 antigen when provided with the rfb iocus from P. aeruginosa serogroup 011 strain PA103 on the recombinant plasmid pLPS2. Eight of the thirteen LPS-rough isolates co-expressed another, presumably endogenous, O antigen when they contained pLPS2. Different subcloned regions of pLPS2 complemented distinct strains to restore endogenous O antigen expression. These data suggest that the loss of O antigen expression by P. aeruginosa CF isolates results from alterations specific to the rfb region, and is not due to mutations involving other loci or ancillary LPS genes. 相似文献
Strains of Pseudomonas aeruginosa initially isolated from patients with cystic fibrosis (CF) often express a smooth lipopolysaccharide (LPS) containing many long O side-chain antigens, but once a chronic infection is established, strains recovered from these patients express little or no LPS O antigen. The genetic basis for this loss of O antigen expression by P. aeruginosa CF isolates is unknown. We report here that 20 CF isoiates of P. aeruginosa , 13 of which are LPS-rough, were each capable of expressing serogroup 011 antigen when provided with the rfb iocus from P. aeruginosa serogroup 011 strain PA103 on the recombinant plasmid pLPS2. Eight of the thirteen LPS-rough isolates co-expressed another, presumably endogenous, O antigen when they contained pLPS2. Different subcloned regions of pLPS2 complemented distinct strains to restore endogenous O antigen expression. These data suggest that the loss of O antigen expression by P. aeruginosa CF isolates results from alterations specific to the rfb region, and is not due to mutations involving other loci or ancillary LPS genes. 相似文献
9.
Abstract.
- 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
- 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
- 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
- 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.
10.
Jerry A. Coyne 《Evolution; international journal of organic evolution》1993,47(3):778-788
Matings between Drosophila simulans females and males of the sibling species D. mauritiana are of abnormally short duration. These rapid matings interrupt the transfer of sperm, leading to substantial reproductive isolation in interspecific as compared to intraspecific copulations. Genetic analysis of this behavior shows that it is influenced much more by the male than the female genotype, with genes from D. simulans being dominant. In males, shortened copulation is caused by interspecific divergence at a minimum of three loci, with one gene on each of the major chromosomes. This is an underestimate of the true number of loci affecting the trait, which could be much larger. The two autosomes have the largest effect, whereas that of the X chromosome is much smaller. The genetic architecture of copulation duration and the larger effect of male than female genotype suggest that females can detect and discriminate against differences in male genitalia. 相似文献