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PubMed1993

Evolutionary adaptation and stress: energy budgets and habitats preferred.

Natural populations are normally exposed to substantial environmental stress. The consequences of stress include elevated metabolic costs and additive genetic variability. From the former, preferred habitats should be located in environments corresponding to minimum total energy expenditure. This tendency occurs in the field for behavioral adaptation of Drosophila to variable temperature (and humidity) conditions. Laboratory studies of resource preference in Drosophila suggest a low genetic variability. However, under more stressful field conditions, genetic variability should be higher. Habitat preference studies under stressful conditions therefore need to be emphasized in modeling situations in nature.

Adaptation, Physiological↗
PubMedDate not supplied

Antimicrobial resistance in Helicobacter pylori: a global overview.

Helicobacter pylori resistance to antimicrobial agents is of particular concern because it is a major determinant in the failure of eradication regimens. Antimicrobial drug resistance has been reported to occur for nitroimidazoles, macrolides, fluoroquinolones, rifampin and tetracyclines. Resistance to nitroimidazoles is the most common, in the range of 30-40% on the average in Europe while the overall prevalence rate of resistance to macrolides is lower, probably ranging between 2-10% in most countries. Development of secondary (acquired) resistance to nitroimidazoles and to the macrolides usually occurs as a rule (> 70-100%) in case of failed eradication therapy. Data available from several centres seems however to indicate that a significant shift towards increasing resistance to metronidazole and to the macrolides might have possibly occurred in many countries over the last years. Resistances to both metronidazole and to clarithromycin are the most significant ones because they influence the success of the treatments although this seems to be less marked and more dependent on the treatment regimens considered in the case of metronidazole resistance than in the setting of clarithromycin resistance. These differences may in part relate to methodological variations and to the inherent difficulties in assessing the susceptibility of H. pylori to metronidazole. It is possible that different resistance cut-off might also have to be considered for metronidazole depending on the treatment regimens administered. The mechanisms of resistance have been well defined for the macrolides and are beginning to be unraveled for the nitroimidazoles. In all cases, resistance of H. pylori to antimicrobial agent seems to be due to the development of single mutational events in chromosomal genes rather than to the acquisition of exogenous resistance genes. Owing to the restricted ability of microbiology laboratories with expertise in H. pylori culture and the lack of standardised methodology for susceptibility testing, H. pylori culture is not often performed routinely. It should however be considered after documented treatment failure or in patients from a geographic area or of an ethnic origin with higher likelihood of antimicrobial drug resistance. Likewise it is deemed very important to institute national and regional surveillance programs to follow the evolution of H. pylori resistance and to better adapt treatment regimens to changes in resistance patterns.

Anti-Bacterial Agents↗
PubMed2004

Evo-Devo of amniote integuments and appendages.

Integuments form the boundary between an organism and the environment. The evolution of novel developmental mechanisms in integuments and appendages allows animals to live in diverse ecological environments. Here we focus on amniotes. The major achievement for reptile skin is an adaptation to the land with the formation of a successful barrier. The stratum corneum enables this barrier to prevent water loss from the skin and allowed amphibian / reptile ancestors to go onto the land. Overlapping scales and production of beta-keratins provide strong protection. Epidermal invagination led to the formation of avian feather and mammalian hair follicles in the dermis. Both adopted a proximal - distal growth mode which maintains endothermy. Feathers form hierarchical branches which produce the vane that makes flight possible. Recent discoveries of feathered dinosaurs in China inspire new thinking on the origin of feathers. In the laboratory, epithelial - mesenchymal recombinations and molecular mis-expressions were carried out to test the plasticity of epithelial organ formation. We review the work on the transformation of scales into feathers, conversion between barbs and rachis and the production of "chicken teeth". In mammals, tilting the balance of the BMP pathway in K14 noggin transgenic mice alters the number, size and phenotypes of different ectodermal organs, making investigators rethink the distinction between morpho-regulation and pathological changes. Models on the evolution of feathers and hairs from reptile integuments are discussed. A hypothetical Evo-Devo space where diverse integument appendages can be placed according to complex phenotypes and novel developmental mechanisms is presented.

Animals↗
PubMed2002

Mitochondrial DNA sequence evolution and phylogeny of the Atlantic Alcidae, including the extinct great auk (Pinguinus impennis).

The Atlantic auk assemblage includes four extant species, razorbill (Alca torda), dovekie (Alle alle), common murre (Uria aalge), and thick-billed murre (U. lomvia), and one recently extinct species, the flightless great auk (Pinguinus impennis). To determine the phylogenetic relationships among the species, a contiguous 4.2-kb region of the mitochondrial genome from the extant species was amplified using PCR. This region included one ribosomal RNA gene, four transfer RNA genes, two protein-coding genes, the control region, and intergenic spacers. Sets of PCR primers for amplifying the same region from great auk were designed from sequences of the extant species. The authenticity of the great auk sequence was ascertained by alternative amplifications, cloning, and separate analyses in an independent laboratory. Phylogenetic analyses of the entire assemblage, made possible by the great auk sequence, fully resolved the phylogenetic relationships and split it into two primary lineages, Uria versus Alle, Alca, and Pinguinus. A sister group relationship was identified between Alca and Pinguinus to the exclusion of ALLE: Phylogenetically, the flightless great auk originated late relative to other divergences within the assemblage. This suggests that three highly divergent species in terms of adaptive specializations, Alca, Alle, and Pinguinus, evolved from a single lineage in the Atlantic Ocean, in a process similar to the initial adaptive radiation of alcids in the Pacific Ocean.

Animals↗
PubMed2004

[An important mission for microbiologists in the new century-cultivation of the unculturable microorganisms].

The present review summarizes the recent advances in cultivating the so-called recalcitrant microorganisms in various natural environments. Firstly, the use of new electron donors and acceptors reveals a list of unique and previously unrecognized physiotypes (Table 1), and the growth supporting reactions include oxidation of phosphite, arsenite, soil humic substances, benzene, Fe (II) and aryl-halides. The novel pure cultures obtained include: Desulfatogenum phosphitoxidans, lithochemotrophic arsenite oxidizing bacteria, Dechloromonas agitata, Dechalosoma suillum, and various Proteobacteria capable of decomposing soil humic substances anaerobically. Secondly, the adaption of nutrient-poor media (down to 1/100 of the traditional concentration), including sea water, soil extract and extension of natural habitats (insect hind-gut, submarine hot vent) are extremely rewarding. For example, cultivation of the ubiquitous SAR11 marine bacterioplankton clade reveals a phylum, small in cell size and genome, but dominating in ocean surface, thus constituting a huge biomass on earth. In addition, the nanosized hyperthermophilic Archaeon from a submarine hot vent, represents an unknown phylum, and because of its symbiotic living with Ignicocous cells, it is named Nanoarchaeum equitans. Its genome size is only 500kb, the smallest for prokaryote. Considering its hyperthermic living environment and small genome, N. equitans may possibly still a primitive form of microbial life and affords an advantageous culture for the study of life origin and evolution on earth. Thirdly, several novel isolation techniques have been developed such as gel microdrop encapsulation and diffusion chamber, both with the advantages of high-throughout operation and simulating to certain extent of the natural environment, thus allowing growth synergy based on cross-feeding to occur. Finally, it should be noted that the cultivation of unculturable microorganisms mentioned in this review does not require expensive and sophisticated equipments and most of the techniques can be adapted in our laboratory at home.

Bacteria↗
PubMed1999

Quantitative variation and selection of esterase gene amplification in Culex pipiens.

Although descriptions of evolutionary mechanisms are common in the literature, very few studies focus on the possible evolution of the adaptive genes themselves, i.e. their quantitative and qualitative changes. Evolution of insecticide resistance in Culex pipiens is a suitable model for studying such processes. In this species, organophosphorous insecticide resistance can be achieved through the overproduction of esterases that sequester the insecticide, and this overproduction can be caused by gene amplification. It is generally assumed, but never verified, that esterase activity, and therefore resistance, is monotonically related to gene amplification. We have analysed resistance, esterase activity and gene amplification in different laboratory strains and natural populations in order to detect variability and to infer effects of selection on these factors. We have shown that resistance, esterase activity and amplification covary, that insecticide selection is able to increase amplification levels, and that a fitness cost is probably attached to the amplification in laboratory strains, related to the level of amplification. The importance of variation in gene amplification level is discussed and some evolutionary implications are proposed.

Animals↗
PubMed1997

Initial frequency of alleles for resistance to Bacillus thuringiensis toxins in field populations of Heliothis virescens.

The risk of rapid pest adaptation to an insecticide is highly dependent on the initial frequency of resistance alleles in field populations. Because we have lacked empirical estimates of these frequencies, population-genetic models of resistance evolution have relied on a wide range of theoretical estimates. The recent commercialization of genetically engineered cotton that constitutively produces an insecticidal protein derived from the biocontrol agent, Bacillus thuringiensis (Bt) has raised concern that we lack data needed to quantify the risk of insect pests such as Heliothis virescens rapidly adapting to this ecologically valuable class of toxins. By individually mating over 2,000 male H. virescens moths collected in four states to females of a Bt toxin-resistant laboratory strain, and screening F1 and F2 offspring for tolerance of the toxic protein, we were able to directly estimate the field frequency of alleles for resistance as 1.5 x 10(-3). This high initial frequency underscores the need for caution in deploying transgenic cotton to control insect pests. Our single-pair mating technique greatly increases the efficiency of detecting recessive resistance alleles. Because alleles that decrease target site sensitivity to Bt toxins and other insecticides are often recessive, this technique could be useful in estimating resistance allele frequencies in other insects exposed to transgenic insecticidal crops or conventional insecticides.

Journal Article↗
PubMed1990

Molecular evolutionary genetics of isozymes: pattern, theory, and application.

Isozyme studies at the population genetics-ecology interface conducted at the Institute of Evolution, University of Haifa, during 15 years, 1974-1989, are reviewed in terms of the evidence, theoretical, and practical implications. These studies involve numerous individuals, populations, species, and higher taxa in nature of plants, animals, and humans tested for variation at 15 to 50 primary isozyme loci. The isozyme studies have been conducted mainly in individuals sampled in natural populations at the local, regional, and global levels. Two of the species studied were wild cereals, the progenitors of wheat and barley in the Near East Fertile Crescent. These studies have been complemented by laboratory controlled a priori experimentation of inorganic and organic pollution biology. The human genetics laboratory compared isozyme structure of Jewish and non-Jewish populations. Our results indicate that: (i) isozyme diversity in nature in abundant, at least partly adaptive, and is oriented and maintained primarily by ecological factors. (ii) Natural selection in action is highlighted by stresses involving among others thermal, chemical, and climatic factors. (iii) Speciation can occur with little change in isozyme diversity. (iv) Jews from diverse countries, and in spite of 2,000 years of Diaspora, retain in the frequencies of some isozymes their Near Eastern origins. (v) Wild cereals harbor rich genetic resources exploitable in breeding either directly as adaptive structures, or indirectly as genetic markers for genotypic production of elite agronomic traits. (vi) Isozymes have been utilized as genetic monitors of marine pollution thereby contributing to environmental quality and conservation. (vii) Isozymes can substantially contribute to conservation biology. (viii) Isozymes have been successfully utilized in constructing molecular phylogenies and in revealing new sibling species. (ix) Future theoretical and practical directions of isozyme studies at the protein and DNA levels are outlined.

Animals↗
PubMed1995

RTM1: a member of a new family of telomeric repeated genes in yeast.

We have isolated a new yeast gene called RTM1 whose overexpression confers resistance to the toxicity of molasses. The RTM1 gene encodes a hydrophobic 34-kD protein that contains seven potential transmembrane-spanning segments. Analysis of a series of industrial strains shows that the sequence is present in multiple copies and in variable locations in the genome. RTM loci are always physically associated with SUC telomeric loci. The SUC-RTM sequences are located between X and Y' subtelomeric sequences at chromosome ends. Surprisingly RTM sequences are not detected in the laboratory strain X2180. The lack of this sequence is associated with the absence of any SUC telomeric gene previously described. This observation raises the question of the origin of this nonessential gene. The particular subtelomeric position might explain the SUC-RTM sequence amplification observed in the genome of yeasts used in industrial biomass or ethanol production with molasses as substrate. This SUC-RTM sequence dispersion seems to be a good example of genomic rearrangement playing a role in evolution and environmental adaptation in these industrial yeasts.

Amino Acid Sequence↗
PubMed2005

What they are, how they work and why they do what they do? The story of SV40-derived gene therapy vectors and what they have to offer.

The natural function of viruses is to deliver their genetic material to cells. Among the most effective of viruses in doing that is Simian Virus-40 (SV40). The properties that make SV40 a successful virus make it an attractive candidate for use as a gene delivery vehicle: high titer replication, infectivity for almost all nucleated cell types whether the cells are dividing or resting, potential for integration into cellular DNA, a peculiar pathway for entering cells that bypasses the cells' antigen processing apparatus, very high stability, and the apparent ability to activate expression of its own capsid genes in trans. Exploiting these and other characteristics of wild type (wt) SV40, increasing numbers of laboratories are studying recombinant (r) SV40-derived vectors. Among the uses to which these vectors have been applied are: delivering therapy to inhibit HIV, hepatitis C virus (HCV) and other viruses; correction of inherited hepatic and other protein deficiencies; immunizing against lentiviral and other antigens; treatment of inherited and acquired diseases of the central nervous system; protecting the lung and other organs from free radical-induced injury; and many others. The effectiveness of these vectors is a reflection of the adaptive evolution that produced their parent virus, wt SV40. This article explores how and why these vectors work, their strengths and their limitations, and provides a functional model for their exploitation for experimental and clinical applications.

Animals↗
PubMed1991

[Lingual orthodontics: why is it progressing?].

At the early stages of the 80's, most of the practitioners and the patients have been seduced by lingual orthodontic. But the difficulties of the technic have rapidly given a disappointment. Today ten years later the authors present the progress which have been realized: the evolution of the brackets, the accuracy of their placement in the lab procedure with the new targ, the making of the wire, the patient's comfort increase. The placement brackets are customized by making an anatomical resin pad. Placement of the brackets have evoluted from a quantized system in two dimensions (Targ 1) to a no quantized system in three dimensions (Class System) and finally to a real quantized system in three dimensions (Targ 2 with a compass of thickness with measures the first order band). Data System DALI (Drawing Arch Lingual Ideal) allows to draw the exact design of the wire. A video tape shows the different laboratory and clinical phases. By using light cured periodontal protection like Barricaid from Caulk: the patients have a greater adaptation with their appliance. All this progress give to lingual orthodontic credibility. Lingual is a reality to day and it's the first concept with customized brackets extremely accuracy, full quantized in the three orders, using the computer progress.

Dental Bonding↗
PubMed1996

Small mammal differentiation on islands.

The reason for the distinctiveness of small mammals on islands has traditionally attracted some imaginative story-telling, usually invoking isolation (as a relict) followed by adaptation and/or random genetic changes. Studies of voles on Orkney, long-tailed field mice on the Hebrides and Shetland, and house mice on the Faroe archipelago show that the main factor in differentiating island races from their mainland ancestors is the chance genetic composition of the founding animals. Subsequent change has necessarily to be based on the genes and frequencies carried by this colonizing group. Probably most post-colonization change is adaptive, although possibly limited in extent both by the initial paucity of variation and by the conservative effect of intragenomic interactions. It is probably helpful to recognize that the 'founder effect' or principle commonly invoked in discussions about evolution on islands involves a founder 'event', followed by founder 'selection'. Island differentiation is not necessarily a precursor to speciation, although the wide occurrence of island endemics suggests that founder effects should not be rejected as a driving force initiating speciation. Notwithstanding, island forms provide a valuable 'laboratory' for testing new genetic combinations, a small proportion of which may prove evolutionarily exciting. Only more empirical studies will uncover their evolutionary importance.

Animals↗
PubMed2002

[Rheumatologic manifestations of Lyme borreliosis].

PURPOSE: Lyme borreliosis is a multisystemic infection caused by the spirochaete Borrelia burgdorferi. In European endemic areas like northeast France, articular manifestations are, after neuroborreliosis, the most frequent extra-cutaneous features observed. Among the pathogenic species of Borrelia, Borrelia burgdorferi sensu stricto is the most frequently identified during Lyme arthritis, but others species also seem to be involved. CURRENT KNOWLEDGE AND KEY POINTS: The diagnosis of Lyme arthritis is usually based on combined clinical data and serological laboratory tests. In atypical forms, detection of bacterial DNA could be useful. While mechanisms involved in acute Lyme arthritis are beginning to be better understood, the pathogenesis of chronic arthritis, which concerns about 10% of the patients, remains unknown. Two hypotheses are proposed to explain the prolonged evolution of the articular disease: a chronic persistence of Borrelia burgdorferi, which evades the host immune system within the joint and/or an autoimmune mechanism by molecular mimicry. The antibiotic therapy is codified in acute arthritis, but is not really adapted in chronic Lyme arthritis or post-Lyme syndrome. FUTURE PROSPECTS AND PROJECTS: To prevent the disease, the vaccine available in the United States does not offer complete protection and is not useful in Europe since the species heterogeneity is important for the outer surface protein A. A better understanding of Lyme disease pathogenesis can subsequently lead to new therapeutic or preventive approaches.

Acute Disease↗
PubMed2025

Reproductive Isolation due to Divergent Ecological Selection Is Accompanied by Vast Genomic Instability in Experimentally Evolved Yeast Populations.

Populations evolving independently in divergent environments accumulate genetic differences and potentially evolve reproductive isolation as a by-product of divergence. The speed and mechanisms underlying this process are difficult to investigate because we rarely get the opportunity to witness them in natural settings, and histories of selection and gene flow between populations are often unknown. Here, we experimentally evolved yeast for 1000 generations of evolution in both divergent and parallel environments. At regular time points during experimental evolution, we made crosses between parallel- and divergent-evolving populations to measure postzygotic reproductive isolation (gamete viability). We used whole genome population sequencing to determine the mutational load, the number and types of structural variation, and other genomic features of the parent, F1 and F2 intraspecific hybrids. We found evidence for large-scale phenotypic and genome-wide differentiation in response to divergent laboratory selection. Divergent-selected populations produced hybrids with reduced gamete viability-a classic signature of postzygotic reproductive isolation in the form of hybrid breakdown. Parallel-selected populations, on the other hand, remained more reproductively compatible (with exceptions). We found that F2 hybrid genomes contained vast genomic instability, that is, new structural variants (especially insertions, deletions and interchromosomal translocations) that were not observed in parent and F1 genomes, which is likely a result of chromosome missegregation and recombination errors in hybrid meiosis. Our results provide phenotypic and genomic evidence that partial reproductive isolation evolved due to adaptation to divergent environments, consistent with predictions of ecological speciation theory.

Reproductive Isolation↗
PubMed2005

Evolution of juvenile growth rates in female guppies (Poecilia reticulata): predator regime or resource level?

Recent theoretical and empirical work argues that growth rate can evolve and be optimized, rather than always being maximized. Chronically low resource availability is predicted to favour the evolution of slow growth, whereas attaining a size-refuge from mortality risk is predicted to favour the evolution of rapid growth. Guppies (Poecilia reticulata) evolve differences in behaviour, morphology and life-history traits in response to predation, thus demonstrating that predators are potent agents of selection. Predators in low-predation environments prey preferentially on small guppies, but those in high-predation environments appear to be non-selective. Because guppies can outgrow their main predator in low- but not high-predation localities, we predict that predation will select for higher growth rates in the low-predation environments.However, low-predation localities also tend to have lower productivity than high-predation localities, yield-ing the prediction that guppies from these sites should have slower growth rates. Here we compare the growth rates of the second laboratory-born generation of guppies from paired high- and low-predation localities from four different drainages. In two out of four comparisons, guppies from high-predation sites grew significantly faster than their low-predation counterparts. We also compare laboratory born descendants from a field introduction experiment and show that guppies introduced to a low-predation environment evolved slower growth rates after 13 years, although this was evident only at the high food level. The weight of the evidence suggests that resource availability plays a more important role than predation in shaping the evolution of growth rates.

Adaptation, Physiological↗
PubMed1999

Female preferences in a fish genus without female mate choice.

The evolution and the adaptive logic (if any) of female mate choice are subjects of lively debate. Whereas most researchers believe that females have evolved to recognize signs of male 'quality' (the ability to provide females or their offspring with direct or indirect genetic or material benefits), there is intriguing evidence that males can evolve to appeal to pre-existing female preferences. Evidence for these pre-existing biases is often ambiguous because phylogenetic reconstructions have usually failed to establish conclusively whether the female preference or the favored male traits evolved first. This potential difficulty is minimal in the mosquitofish genus Gambusia, none of whose 45 species appears to have a female-choice mating system in the wild, and none of which shows the male behavioral and morphological traits that are characteristic of female choice. Nevertheless, in an experimental situation in the laboratory, female Gambusia holbrooki readily chose between models of males and demonstrated significant and reliable preferences for a variety of exaggerated male traits that are not seen in their species or their genus. Other morphological alterations were not preferred. The latent willingness of females to choose traits in a genus without such traits and without evident female choice in the wild is remarkable and may indicate a pre-existing bias in females that is ready to drive male evolution, should the social system or the ecological variables that control it change.

Animals↗
PubMed1998

Physical activity, energy expenditure and fitness: an evolutionary perspective.

The model for human physical activity patterns was established not in gymnasia, athletic fields, or exercise physiology laboratories, but by natural selection acting over eons of evolutionary experience. This paper examines how evolution has determined the potential for contemporary human performance, and advances the experience of recently-studied hunter-gatherers as the best available (although admittedly imperfect) indicator of the physical activity patterns for which our genetically determined biology was originally selected. From the emergence of the genus Homo, over 2 million years ago (MYA), until the agricultural revolution of roughly 10000 years ago our ancestors were hunter-gatherers, so the adaptive pressures inherent in that environmental niche have exerted defining influence on human genetic makeup. The portion of our genome that determines basic anatomy and physiology has remained relatively unchanged over the past 40 000 years. Thus, the complex interrelationship between energy intake, energy expenditure and specific physical activity requirements for current humans remains very similar to that originally selected for Stone Age men and women who lived by gathering and hunting. Research investigating optimal physical activity for human health and performance can be guided by understanding the evolution of physical activity patterns in our species.

Animals↗
PubMed1999

Does interspecific hybridization influence evolutionary rates? An experimental study of laboratory adaptation in hybrids between Drosophila serrata and Drosophila birchii.

The low initial fitness of progeny from interspecific crosses in animals and the rarity of interspecific hybridization in natural environments have led to a debate about the evolutionary importance of this phenomenon. Here we directly assess the effects of hybridization between Drosophila serrata and Drosophila birchii on evolutionary rates. We looked at the effects on laboratory adaptation over 30 generations in two laboratory environments, one of which involved nutrition and temperature stress. Laboratory adaptation occurred over time in both environments as reflected by a marked change in viability. However, whilst hybrid lines at no stage performed poorly relative to parental lines, their rate of adaptation never exceeded that of the parentals. Thus, there was no evidence that hybridization increased evolutionary rates. Instead, hybrid lines converged phenotypically with one of the parental species.

Analysis of Variance↗