Bugs and mammoths. Extinction by germs?
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Results for “Extinction, Biological”
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Advantages of multi-color fluorescent proteins for whole-body and in vivo cellular imaging.
The revolution of in vivo cancer biology enabled by fluorescent proteins is described. The high extinction coefficients, quantum yields, and unique spectral properties of fluorescent proteins have been taken advantage of in order to visualize, in real time, the important aspects of cancer in living animals, including tumor cell trafficking, invasion, metastasis, and angiogenesis. Fluorescent proteins enable whole-body imaging of tumors on internal organs. These multicolored proteins have allowed the color-coding of cancer cells growing in vivo with distinction of different cell types, including host from tumor, with single-cell resolution.
Animals↗
Potential biological indicators for glutaraldehyde and formaldehyde sterilization processes.
The present study aimed to isolate, select, and evaluate bacterial isolates with potential for use as biological indicators for sterilization with glutaraldehyde and/or formaldehyde. A total of 340 local Bacillus isolates were screened for glutaraldehyde and/or formaldehyde resistance by determination of minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and extinction time and were compared with B. subtilis (var. niger) ATCC 9372, the biological indicator for ethylene oxide sterilization, as reference. Of these, 85 isolates had glutaraldehyde MICs of 0.5% or higher, while 29 had formaldehyde MICs of 0.04% or higher. Of the 29 resistant isolates, 15 had MBCs of 0.05% or more. Extinction times were used to evaluate the bactericidal/sporicidal activity of glutaraldehyde. Eight had inactivation times of more than 5 h in 2% glutaraldehyde (pH 8), whereas 12 had inactivation times of more than 3 h in l% formaldehyde, with one isolate in common. These 19 isolates were selected and evaluated as potential biological indicators for aldehydes by determination of the decimal reduction times ( D values), compared with the reference strain. Eight glutaraldehyde-resistant isolates exhibited D values 2.0- to 3.5-fold higher than the reference strain (30 min.). Only five of 12 formaldehyde resistant isolates had D values higher than that of the reference strain. Using six resistant isolates, temperature coefficient values between 2.11 and 3.02 were obtained for 2% formaldehyde. Finally, 14 isolates were tested for potential pathogenicity and were identified to species level. All of the eight glutaraldehyde-resistant isolates, including the isolate with dual resistance, and three formaldehyde-resistant isolates were B. licheniformis, while two other formaldehyde-resistant isolates were B. cereus. Six of the selected B. licheniformis isolates are potential biological indicators for sterilization processes using aldehydes. Three can be suggested for glutaraldehyde only and three for both aldehydes.
Bacillus subtilis↗
Lateral plate evolution in the threespine stickleback: getting nowhere fast.
Gasterosteus aculeatus is a small Holarctic fish with marine, anadromous, and freshwater populations. Marine and anadromous populations apparently have changed little in the past 10 million years and exhibit limited geographical variation. In contrast, freshwater isolates have been founded repeatedly by marine and anadromous populations, and post-glacial isolates have undergone extraordinary adaptive radiation. Stickleback traits that have diversified during post-glacial radiation, including the 'lateral plates' (LP), can evolve substantially within decades after colonization of fresh water or when the environment (particularly predation regime) changes. Although highly divergent freshwater isolates of G. aculeatus have existed for at least 10 million years, they have rarely experienced sustained evolutionary divergence leading to formation of widespread, phenotypically distinct species. The paradox of rapid LP evolution without sustained divergence has resulted from selective extinction of highly divergent populations, because they are specialized for conditions in small, isolated habitats that tend to dry up within limited periods. Biological species of G. aculeatus may also evolve within decades, and are also prone to extinction because they are endemic to and specialized for small, ephemeral habitats. The high rate of evolution observed in contemporary threespine stickleback populations may not be unique to this species complex and has important implications for use of post-glacial populations in comparative studies, speciation rate, and discrimination of sympatric and allopatric speciation.
Animals↗
Aromatized arborane/fernane hydrocarbons as biomarkers for cordaites.
Previous palaeobotanical and palynological studies on coals from Euramerican Pennsylvanian ( identical with Late Carboniferous) coal basins indicate a major change in coal-swamp floras, especially at the Westphalian-Stephanian ( approximately Kasimovian-Gzhelian, according to Geological Time Scale 2004) boundary. A flora dominated by arborescent lycophytes was replaced by a vegetation dominated by marattialean tree ferns in various Euramerican coal basins. Earlier combined palynological and organic geochemical studies on Westphalian/Stephanian coals and shales from the Saar-Nahe Basin (Germany) revealed that the distribution of aromatized arborane/fernane hydrocarbons in solvent extracts reflects the increasing importance of seed plants, especially cordaites (extinct group of gymnosperms), conifers and pteridosperms. However, the biological source of the precursor molecules could not be specified. To clarify if the arborane/fernane derivatives MATH, MAPH, DAPH 1, and DAPH 2 in Westphalian/Stephanian coals can be assigned to one of the three potential source plant groups, we analyzed coals, sediments and fossil plant remains from different Euramerican locations with respect to their biomarker composition and stable carbon isotopic composition. Thereby, stable carbon isotopic ratios showed only insignificant variations between Westphalian and Stephanian samples and proved to be an unsuitable tool to describe floral changes during the Westphalian/Stephanian of the Saar-Nahe Basin. In contrast, we were able to show for the first time that MATH, MAPH, DAPH 1 and DAPH 2 are prominent constituents only in extracts of cordaitean macrofossils and can therefore be regarded as biomarkers for this group of gymnosperms.
Biomarkers↗
A kill curve for Phanerozoic marine species.
A kill curve for Phanerozoic species is developed from an analysis of the stratigraphic ranges of 17,621 genera, as compiled by Sepkoski. The kill curve shows that a typical species' risk of extinction varies greatly, with most time intervals being characterized by very low risk. The mean extinction rate of 0.25/m.y. is thus a mixture of long periods of negligible extinction and occasional pulses of much higher rate. Because the kill curve is merely a description of the fossil record, it does not speak directly to the causes of extinction. The kill curve may be useful, however, to li¿mit choices of extinction mechanisms.
Animals↗
CO2 and the end-Triassic mass extinction.
The end of the Triassic period was marked by one of the largest and most enigmatic mass-extinction events in Earth's history and, with few reliable marine geochemical records, terrestrial sediments offer an important means of deciphering environmental changes at this time. Tanner et al. describe an isotopic study of Mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide (pCO2) across the Triassic-Jurassic boundary was relatively constant (within 250 p.p.m.v.), but this is inconsistent with high-resolution evidence from the stomatal characters of fossil leaves. Here I show that the temporal resolution of the fossil-soil samples may have been inadequate for detecting a transient rise in pCO2. I also show that the fossil-soil data are consistent with a large increase in pCO2 across the Triassic-Jurassic boundary when variations in the stable carbon isotope (denoted as delta13C) in terrestrial plant leaves are taken into account. These factors suggest that the linkage between pCO2, global warming and the end-Triassic mass extinction remains intact.
Atmosphere↗
The role of extinction in evolution.
The extinction of species is not normally considered an important element of neodarwinian theory, in contrast to the opposite phenomenon, speciation. This is surprising in view of the special importance Darwin attached to extinction, and because the number of species extinctions in the history of life is almost the same as the number of originations; present-day biodiversity is the result of a trivial surplus of originations, cumulated over millions of years. For an evolutionary biologist to ignore extinction is probably as foolhardy as for a demographer to ignore mortality. The past decade has seen a resurgence of interest in extinction, yet research on the topic is still at a reconnaissance level, and our present understanding of its role in evolution is weak. Despite uncertainties, extinction probably contains three important elements. (i) For geographically widespread species, extinction is likely only if the killing stress is one so rare as to be beyond the experience of the species, and thus outside the reach of natural selection. (ii) The largest mass extinctions produce major restructuring of the biosphere wherein some successful groups are eliminated, allowing previously minor groups to expand and diversify. (iii) Except for a few cases, there is little evidence that extinction is selective in the positive sense argued by Darwin. It has generally been impossible to predict, before the fact, which species will be victims of an extinction event.
Animals↗
Global patterns in endemism explained by past climatic change.
I propose that global patterns in numbers of range-restricted endemic species are caused by variation in the amplitude of climatic change occurring on time-scales of 10-100 thousand years (Milankovitch oscillations). The smaller the climatic shifts, the more probable it is that palaeoendemics survive and that diverging gene pools persist without going extinct or merging, favouring the evolution of neoendemics. Using the change in mean annual temperature since the last glacial maximum, estimated from global circulation models, I show that the higher the temperature change in an area, the fewer endemic species of mammals, birds, reptiles, amphibians and vascular plants it harbours. This relationship was robust to variation in area (for areas greater than 10(4) km2), latitudinal position, extent of former glaciation and whether or not areas are oceanic islands. Past climatic change was a better predictor of endemism than annual temperature range in all phylads except amphibians, suggesting that Rapoport's rule (i.e. species range sizes increase with latitude) is best explained by the increase in the amplitude of climatic oscillations towards the poles. Globally, endemic-rich areas are predicted to warm less in response to greenhouse-gas emissions, but the predicted warming would cause many habitats to disappear regionally, leading to species extinctions.
Adaptation, Physiological↗
Sex causes altruism. Altruism causes sex. Maybe.
This study presents a mathematical model in which the fitness of an individual depends on the individual's genotype (individual effects) and on the genotypes of other members of the individual's local group (group effects). The findings suggest that, if phenotypes are a result of complex interactions between genes at different loci, then fitness-enhancing group effects may become common in sexual populations. The spread of fitness-enhancing group effects is facilitated when environmental conditions sometimes deteriorate temporarily. This is so even if the genotypes with the highest group effects also tend to have relatively low individual effects. In this sense, the process described here can lead to the evolution of altruism. By contrast, when populations are asexual it appears that group effects are much less important in determining the outcome of evolution. Thus, in nature, asexual populations may tend to be characterized by more antagonistic interactions than those that typically prevail when reproduction is sexual. This might help to explain why asexual lineages are prone to rapid extinction.
Altruism↗
[The return of the Red Queen, or the law of the growth in the mean duration of the existence of genera during evolution].
Phanerozoic marine genera apparently do not become less extinction-prone with age. Higher extinction probability in "young" cohorts of genera is better explained by initially different levels of extinction-tolerance of genera in the cohort. This fact agrees with one of the two basic statements of the "Red Queen" hypothesis (Van Valen, 1973). In the second statement (the idea that the increase in fitness lowers extinction probability) the term "fitness" should be changed to "adaptability". The increase of extinction-tolerance, that can be interpreted as the increase of adaptability to unpredictable changes of environment, is found in succession of "generations" of genera that replace one another through time. This increase reveals itself, firstly, in the growth of mean duration of genera, as well as in the decrease of extinction/origination rates, gradual accumulation of long-lived genera and origination of genera with higher duration. The increase of adaptability may be caused by selective extinction of stenotopic, ecologically specialized forms; Cope's law; evolution of ecosystems that involves development of more effective mechanisms of sustaining homeostasis which may stimulate the recovery of a genus after partial extinction.
Aging↗
Multiple factors in the reptile extinctions of the Cretaceous period.
The selective extinction of the dinosaurs and other giant reptiles has long been a topic of speculation and controversy. Everyone is familiar with the theory of the giant bollide colliding with Earth. But, would it not be more likely that that multiple factors acted over a relatively long period of time to produce this mass extinction?
Animals↗
[Profile of antinuclear antibodies in 14 cases of extinct systemic lupus erythematosus for more than 3 years].
In order to study the profile of antinuclear antibodies (ANA) and anticytoplasm in the clinical recovery period, we searched for ANA by 4 methods (indirect immunofluorescence on HEp-2 and Crithidia luciliae cells, double diffusion in agar against veal thymus and human spleen, immunoprint with a total extract of HeLa cells) in 14 patients with SLE extinct since more than 3 years. The population under study consisted of 12 women and 2 men, aged 43 years on average at the time of study (extremes: 28-64 years). The average lapse of time between the diagnosis of SLE and date of sampling is of 12.6 years (extremes: 3-22 years). The average remission/clinical recovery time during the study is of 8.9 years (extremes: 3-22 years). Seven patients were administered mild corticotherapy (average dose of prednisone: 4.7 mg/day). All the sera preserved ANA or anticytoplasm, distributed in the following way: presence of antinucleus: 10/14 (71.5%); average titre 40; speckled aspect: 10/10; presence of anti-DNA: 0/14; presence of anti-ECT: 2/14 (14.3%): anti-SSB 1 case, anti-RNP 1 case; positive immunoprint: 12/14 (85.7%): anti-Sm 5 cases (isolated or associated), isolated anti-SSB 2 cases; isolated anti-Ro 2 cases; various unidentified 3 cases. These results suggest that the production of ANA and anticytoplasm other than anti-DNA continues during the period of clinical extinction of SLE, underlining the rarity of a complete biological recovery and the necessity of long term clinical surveillance.
Adult↗
[Current problems in the microbiological control of food].
The paper deals with a number of aspects of current interest and significance on the subject of the microbiological testing of food with particular reference to the role of research institutes. The main objectives of microbiological testing of food are essentially two: (i) to establish the absence of a human health hazard due to microbial contamination of food (food safety); and (ii) to define the quality standard of food (food quality). As far as the first of these objectives is concerned, the outcome of the assay necessarily emerges not only from identification of pathogens but also from definition of their pathogenicity and virulence characteristics and of critical factors for their transmission. Alongside the classic pathogens, evidence has recently been found indicating that four additional bacteria, namely Yersinia enterocolitica, Campylobacter jejuni, Vibrio cholerae non 0-1 and Listeria monocytogenes, also play an important role in food-borne disease. The most characteristic biological, ecological and epidemiologic aspects related to human food-borne disease are described for these bacteria. As regards the second objective, i.e. food quality, stress is laid on the role played by microbial indicators and their predictivity for pathogenic micro-organisms, which does not always exist. This depends on three basic differential factors: (i) biological characteristics giving rise to different diffusion, dilution and extinction phenomena, or, on the other hand, multiplication of such pathogens in the environment and in food; (ii) resistance to the natural inactivation mechanisms, whether of a general or specific nature, of each alimentary substrate; and (iii) the ecological and epidemiological pattern. By way of examples, two experiences indicating the lack of predictivity of the faecal indicators for enterovirus and Vibrio cholerae non 0-1 are reported. Nevertheless, standard microbiological testing for mesophilic flora and indicators are fundamental instruments in the analysis of food quality at all stages of production (supply of raw materials, good manufacturing practices, characteristics of the product during shelf life), and this type of testing, when performed by industrial-scale food producers, may guarantee a high standard of food quality and its progressive improvement.
Campylobacter↗
Biological effects of stellar collapse neutrinos
Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia, and oncogenesis. Using a conventional model of the galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined.
Animals↗
A ratio-dependent food chain model and its applications to biological control.
While biological controls have been successfully and frequently implemented by nature and human, plausible mathematical models are yet to be found to explain the often observed deterministic extinctions of both pest and control agent in such processes. In this paper we study a three trophic level food chain model with ratio-dependent Michaelis-Menten type functional responses. We shall show that this model is rich in boundary dynamics and is capable of generating such extinction dynamics. Two trophic level Michaelis-Menten type ratio-dependent predator-prey system was globally and systematically analyzed in details recently. A distinct and realistic feature of ratio-dependence is its capability of producing the extinction of prey species, and hence the collapse of the system. Another distinctive feature of this model is that its dynamical outcomes may depend on initial populations levels. Theses features, if preserved in a three trophic food chain model, make it appealing for modelling certain biological control processes (where prey is a plant species, middle predator as a pest, and top predator as a biological control agent) where the simultaneous extinctions of pest and control agent is the hallmark of their successes and are usually dependent on the amount of control agent. Our results indicate that this extinction dynamics and sensitivity to initial population levels are not only preserved, but also enriched in the three trophic level food chain model. Specifically, we provide partial answers to questions such as: under what scenarios a potential biological control may be successful, and when it may fail. We also study the questions such as what conditions ensure the coexistence of all the three species in the forms of a stable steady state and limit cycle, respectively. A multiple attractor scenario is found.
Animals↗
Evolutionary dynamics and highly optimized tolerance.
We develop a numerical model of a lattice community based on Highly Optimized Tolerance (HOT), which relates the evolution of complexity to robustness tradeoffs in an uncertain environment. With the model, we explore scenarios for evolution and extinction which are abstractions of processes which are commonly discussed in biological and ecological case studies. These include the effects of different habitats on the phenotypic traits of the organisms, the effects of different mutation rates on adaptation, fitness, and diversity, and competition between generalists and specialists. The model exhibits a wide variety of microevolutionary and macroevolutionary phenomena which can arise in organisms which are subject to random mutation, and selection based on fitness evaluated in a specific environment. Generalists arise in uniform habitats, where different disturbances occur with equal frequency, while specialists arise when the relative frequency of different disturbances is skewed. Fast mutators are seen to play a primary role in adaptation, while slow mutators preserve well-adapted configurations. When uniform and skewed habitats are coupled through migration of the organisms, we observe a primitive form of punctuated equilibrium. Rare events in the skewed habitat lead to extinction of the specialists, whereupon generalists invade from the uniform habitat, adapt to their new surroundings, ultimately leading their progeny to become vulnerable to extinction in a subsequent rare disturbance.
Adaptation, Physiological↗