The other mediator for adherence of Haemophilus influenzae organisms without involvement of fimbriae.

The number of the nontypeable Haemophilus influenzae (HiN) organisms that adhered to the primary mouse fetal lung cells was significantly more than type b Haemophilus influenzae (Hib) organisms. The average number of HiN organisms adherent to host cells was 2,291/100 host cells (range, 1,654-3,182), but that of Hib was markedly reduced to 147/100 host cells (range, 102-238). In this case, P value was less than 0.05 by using a paired Student t-test. The sonicated extract from HiN TMS11 organisms inhibited adherence of H. influenzae TMS11 organisms to monolayer at 76.3% and it inhibited adherence of Hib TMS24 organisms at 92.3%. This result indicates that a mediator existing on the surface of HiN organisms may be the same as that on type b organisms. The number of detected organisms in broncho and lung tissues 3 days after intranasal infection with HiN strains was significantly greater than that in infection with Hib strains. Therefore, in vitro adhesive capacity of H. influenzae organisms was correlative to infectivity by intranasal injection.     

Biological traits interact with human threats to drive extinctions: A modelling study

How a particular threat influences extinction risk may depend on biological traits. Empirical studies relating threats and traits are needed, but data are scarce, making simulations useful. We implemented an eco-evolutionary model to analyse how five threat types influence the extinction risk of virtual organisms differing in body size, maturity age, fecundity, and dispersal ability. The model consisted of observing the evolutionary shift in the mean trait values of an assemblage of organisms when a threat was added into the virtual world where they lived. If a positive shift was found in trait values, we considered that the threat negatively influenced organisms with lower values for that trait. Direct killing mostly affected organisms with slow life cycles (slower-living) and poorly dispersive organisms. Habitat loss caused a reduction in the average dispersal ability of organisms. Habitat fragmentation caused an increase of average dispersal ability, and had a negative effect on larger, less fecund organisms. Habitat degradation and the introduction of invasive competitors had similar effects, mostly affecting large and fast-living organisms, with habitat degradation also affecting highly fecund and poorly dispersive organisms. These results agree with previous empirical studies in which larger, slower-lived, and less fecund organisms are more vulnerable to a greater range of threats. On the other hand, our results challenge two commonly seen hypotheses in the literature: that organisms with high dispersal ability fare well under any high habitat loss scenarios, and that fast-living, highly fecund organisms always do well during environmental change. Our study shows that highly dispersive organisms may be the losers when habitat loss removes large continuous areas of habitat, and fast-living and highly reproductive organisms may be the losers when resources or energy availability dwindle to very low levels. Most importantly, our study underpins the importance of considering the type of threat when analysing the relation between traits and extinction. Even in simple scenarios such as the ones modelled here, different threats lead to different, sometimes opposite, extinction probabilities according to the biological traits of organisms.     

Are certain life histories particularly prone to local extinction?

Using stochastic simulations and elasticity analysis, we show that there are inherent differences in the risk of extinction between life histories with different demographies. Which life history is the most vulnerable depends on which vital rate varies. When juvenile survival varies semelparous organisms with delayed reproduction are the most vulnerable ones, while a varying developmental rate puts a greater threat to semelparous organisms with rapid development. Iteroparous organisms are the most vulnerable ones when adult survival varies. Generally, we do not expect to observe organisms in nature having variation in vital rates that produce a high risk of extinction. Given the results here we therefore predict that iteroparous organisms should show low variation in adult survival. Moreover, we predict that semelparous organisms should show low variation in juvenile survival and low variation in developmental rate. The effect of temporal correlation on extinction risk is most pronounced in organisms with semelparous life histories.     

Organism size promotes the evolution of specialized cells in multicellular digital organisms

Specialized cells are the essence of complex multicellular life. Fossils allow us to study the modification of specialized, multicellular features such as jaws, scales, and muscular appendages. But it is still unclear what organismal properties contributed to the transition from undifferentiated organisms, which contain only a single cell type, to multicellular organisms with specialized cells. Using digital organisms I studied this transition. My simulations show that the transition to specialized cells happens faster in organism composed of many cells than in organisms composed of few cells. Large organisms suffer less from temporarily unsuccessful evolutionary experiments with individual cells, allowing them to evolve specialized cells via evolutionary trajectories that are unavailable to smaller organisms. This demonstrates that the evolution of simple multicellular organisms which are composed of many functionally identical cells accelerates the evolution of more complex organisms with specialized cells.     

Cost of resistance to parasites in digital organisms

Virtually all organisms are attacked by parasites and are therefore expected to evolve resistance against these natural enemies. Parasite resistance is costly in a wide range of organisms, although the generality of such costs has been questioned, especially when resistance is not based on reallocation of resources. Digital organisms are increasingly used to explore aspects of life in general. In the Tierra system, there is a trade-off between resistance against parasites and competitive ability. Because digital organisms are too simple to store resources, the finding that resistance to parasites is costly in digital organisms suggests that costs of parasite resistance can also occur when resistance is not resource based.     

On the evolutionary origin of aging

It is generally believed that the first organisms did not age, and that aging thus evolved at some point in the history of life. When and why this transition occurred is a fundamental question in evolutionary biology. Recent reports of aging in bacteria suggest that aging predates the emergence of eukaryotes and originated in simple unicellular organisms. Here we use simple models to study why such organisms would evolve aging. These models show that the differentiation between an aging parent and a rejuvenated offspring readily evolves as a strategy to cope with damage that accumulates due to vital activities. We use measurements of the age-specific performance of individual bacteria to test the assumptions of the model, and find evidence that they are fulfilled. The mechanism that leads to aging is expected to operate in a wide range of organisms, suggesting that aging evolved early and repeatedly in the history of life. Aging might thus be a more fundamental aspect of cellular organisms than assumed so far.     

To be or not to be rhythmic? A review of studies on organisms inhabiting constant environments

Abstract

Circadian clocks are endogenous time keeping mechanisms that drive near 24-h behavioural, physiological and metabolic rhythms in organisms. It is thought that organisms possess circadian clocks to facilitate coordination of essential biological events to the external day and night (extrinsic advantage) so as to enhance Darwinian fitness. However, on Earth, there are a number of habitats that are not subject to such robust daily cycling of geo-physical factors. Do organisms living under such conditions exhibit rhythmic behaviours that are driven by endogenous circadian clocks? We attempt to critically survey studies of rhythms (or the lack of them) in organisms living in a range of constant environments. Many such organisms do show rhythms in behaviour and/or physiological variables. We suggest that such presence of rhythms may be indicative of an underlying clock that facilitates, (a) internal synchrony among rhythms, and (b) temporal partitioning of incompatible cellular processes (intrinsic advantage). We then highlight reasons that limit our interpretations about the presence (or absence) of clocks in such organisms living under constant conditions, and suggest possible methods to conclusively test whether or not rhythms in these organisms are driven by endogenous circadian clocks with the hope that it may enhance our understanding of circadian clocks in organisms under constant environments.     

Programmed cell death in trypanosomatids and other unicellular organisms

In multicellular organisms, cellular growth and development can be controlled by programmed cell death (PCD), which is defined by a sequence of regulated events. However, PCD is thought to have evolved not only to regulate growth and development in multicellular organisms but also to have a functional role in the biology of unicellular organisms. In protozoan parasites and in other unicellular organisms, features of PCD similar to those in multicellular organisms have been reported, suggesting some commonality in the PCD pathway between unicellular and multicellular organisms. However, more extensive studies are needed to fully characterise the PCD pathway and to define the factors that control PCD in the unicellular organisms. The understanding of the PCD pathway in unicellular organisms could delineate the evolutionary origin of this pathway. Further characterisation of the PCD pathway in the unicellular parasites could provide information regarding their pathogenesis, which could be exploited to target new drugs to limit their growth and treat the disease they cause.     

Evolution of stress response in the face of unreliable environmental signals

Most organisms live in ever-changing environments, and have to cope with a range of different conditions. Often, the set of biological traits that are needed to grow, reproduce, and survive varies between conditions. As a consequence, organisms have evolved sensory systems to detect environmental signals, and to modify the expression of biological traits in response. However, there are limits to the ability of such plastic responses to cope with changing environments. Sometimes, environmental shifts might occur suddenly, and without preceding signals, so that organisms might not have time to react. Other times, signals might be unreliable, causing organisms to prepare themselves for changes that then do not occur. Here, we focus on such unreliable signals that indicate the onset of adverse conditions. We use analytical and individual-based models to investigate the evolution of simple rules that organisms use to decide whether or not to switch to a protective state. We find evolutionary transitions towards organisms that use a combination of random switching and switching in response to the signal. We also observe that, in spatially heterogeneous environments, selection on the switching strategy depends on the composition of the population, and on population size. These results are in line with recent experiments that showed that many unicellular organisms can attain different phenotypic states in a probabilistic manner, and lead to testable predictions about how this could help organisms cope with unreliable signals.     

Multiple, Novel Biologically Active Endophytic Actinomycetes Isolated from Upper Amazonian Rainforests

Microbial biodiversity provides an increasingly important source of medically and industrially useful compounds. We have isolated 14 actinomycete species from a collection of approximately 300 plant stem samples from the upper Amazonian rainforest in Peru. All of the cultured isolates produce substances with inhibitory activity directed at a range of potential fungal and bacterial pathogens. For some organisms, this activity is very broad in spectrum while other organisms show specific activity against a limited number of organisms. Two of these organisms preferentially inhibit bacterial test organisms over eukaryotic organisms. rDNA sequence analysis indicates that these organisms are not equivalent to any other cultured deposits in GenBank. Our results provide evidence of the untapped biodiversity in the form of biologically active microbes present within the tissues of higher plants.     

The choice of model organisms in evo-devo

Study of the model organisms of developmental biology was crucial in establishing evo-devo as a new discipline. However, it has been claimed that this limited sample of organisms paints a biased picture of the role of development in evolution. Consequently, judicious choice of new model organisms is necessary to provide a more balanced picture. The challenge is to determine the best criteria for choosing new model organisms, given limited resources.     

DNA and the theory of stabilizing selection

A comparison of structural-functional features of genomic DNAs allowed to estimate the role of internal and external factors in evolution of different groups of organisms. The basic difference between higher and lower organisms has been demonstrated. It is reflected in the difference of their reaction on to external factors in accordance with two adaptation types, the openness and autonomization. There is a correlation between structural-functional organization of genomic DNAs of higher and lower organisms and the above mentioned types of adaptation. DNA of lower organisms has been proposed to be characterized as "labile", and that of higher organisms, as "stable". The "DNA lability" means high mutation ability, which characterizes the existence of and evolution of lower organisms (genetic inconstancy of the lower organisms). On the contrary, "DNA stability" means the creation of stable genetic apparatus, reduction of variability in higher organisms (genetic constancy of higher organisms). This suggests the existence of the two principal ways of evolution.     

Darwin, historical biogeography, and the importance of overcoming binary opposites

It is well known that Darwin and Wallace came to discover the phenomenon of evolution through a historical approach to the geographical distribution of organisms. Before Darwin, evolution was a mere speculation that could be invoked to explain some facts. Darwin's biogeographical argument for evolution is based largely on three main explanatory hypotheses. The first is that the geographical distribution of organisms is historically informative. The second hypothesis is that long-distance dispersal over barriers is one main force (extinction is the other) that modifies the distribution of organisms. The third of Darwin's biogeographical hypotheses is that the factors that shape the distribution of organisms are mainly historical (large, often global and long temporal scales) rather than ecological (small spatial and short temporal scales). From the time of Darwin until now, a wide spectrum of biogeographical schools have provided new insights that challenge the central role of space, dispersal and history as the main explanatory hypotheses for the distribution of organisms, generating three binary opposites: (1) the spatial dimension of evolution: geographical distribution of organisms as historically informative vs. historically uninformative; (2) the processes that modify the geographical distribution of organisms: dispersal vs. vicariance; and (3) the explanation of geographical distribution: history vs. ecology. We analyse these three binary opposites to show that the components of each are complementary rather than antagonistic approaches to the study of biogeography.     

Selective potentiation of host resistance in mice following treatment with Pyrexol

The purpose of this study was to examine the effect of treatment with the biologic response modifier Pyrexol on murine host resistance to various infectious organisms. Adult female CD1 mice were treated with a single subcutaneous 100-micrograms injection of Pyrexol at 14, 7, 5, 2, or 1 day prior to infection with various infectious organisms. These organisms included the Herpes simplex type 2 and influenza viruses, as well as the bacteria Listeria monocytogenes and Streptococcus zooepidemicus. Pyrexol treatment was found to significantly potentiate resistance to Listeria organisms, but had no appreciable effect on resistance to any of the other organisms tested. Previous reports have demonstrated that treatment with Pyrexol augments a number of cell-mediated immune parameters, several of which have been shown to be responsible for the elimination of Listeria organisms. These results suggest that Pyrexol is capable of selectively potentiating host resistance to infection.     

Beyond society: the evolution of organismality

The evolution of organismality is a social process. All organisms originated from groups of simpler units that now show high cooperation among the parts and are nearly free of conflicts. We suggest that this near-unanimous cooperation be taken as the defining trait of organisms. Consistency then requires that we accept some unconventional organisms, including some social insect colonies, some microbial groups and viruses, a few sexual partnerships and a number of mutualistic associations. Whether we call these organisms or not, a major task is to explain such cooperative entities, and our survey suggests that many of the traits commonly used to define organisms are not essential. These non-essential traits include physical contiguity, indivisibility, clonality or high relatedness, development from a single cell, short-term and long-term genetic cotransmission, germ–soma separation and membership in the same species.     

On the mechanisms involved in biological heme crystallization

Blood-feeding organisms digest hemoglobin, releasing large quantities of heme inside their digestive tracts. Free heme is very toxic, and these organisms have evolved several mechanisms to protect against its deleterious effects. One of these adaptations is the crystallization of heme into the dark-brown pigment hemozoin (Hz). Here we review the process of Hz formation, focusing on organisms other than Plasmodium that have contributed to a better understanding of heme crystallization. Hemozoin has been found in several distinct classes of organisms including protozoa, helminths and insects and Hz formation is the predominant form of heme detoxification. The available evidence indicates that amphiphilic structures such as phospholipid membranes and lipid droplets accompanied by specific proteins play a major role in heme crystallization. Because this process is specific to a number of blood-feeding organisms and absent in their hosts, Hz formation is an attractive target for the development of novel drugs to control illnesses associated with these hematophagous organisms.     

A twelve-step program for evolving multicellularity and a division of labor

The volvocine algae provide an unrivalled opportunity to explore details of an evolutionary pathway leading from a unicellular ancestor to multicellular organisms with a division of labor between different cell types. Members of this monophyletic group of green flagellates range in complexity from unicellular Chlamydomonas through a series of extant organisms of intermediate size and complexity to Volvox, a genus of spherical organisms that have thousands of cells and a germ-soma division of labor. It is estimated that these organisms all shared a common ancestor about 50 +/- 20 MYA. Here we outline twelve important ways in which the developmental repertoire of an ancestral unicell similar to modern C. reinhardtii was modified to produce first a small colonial organism like Gonium that was capable of swimming directionally, then a sequence of larger organisms (such as Pandorina, Eudorina and Pleodorina) in which there was an increasing tendency to differentiate two cell types, and eventually Volvox carteri with its complete germ-soma division of labor.     

Bacteria as a new model system for aging studies: investigations using light microscopy

Aging-the decline in an individual's condition over time-is at the center of an active research field in medicine and biology. Some very basic questions have, however, remained unresolved, the most fundamental being: do all organisms age? Or are there organisms that would continue to live forever if not killed by external forces? For a long time it was believed that aging only affected organisms such as animals, plants, and fungi. Bacteria, in contrast, were assumed to be potentially immortal and until recently this assertion remained untested. We used phase-contrast microscopy (on an Olympus BX61) to follow individual bacterial cells over many divisions to prove that some bacteria show a distinction between an aging mother cell and a rejuvenated daughter, and that these bacteria thus age. This indicates that aging is a more fundamental property of organisms than was previously assumed. Bacteria can now be used as very simple model system for investigating why and how organisms age.     

玉米和花生根际生物的原位观察初探*

利用改进根箱法对玉米和花生根际生物进行了原位采样和观察。采用载玻片贴片方法直接采集到作物根系分泌物中的生物,并用荧光显微镜进行观察。花生根系分泌物中分布有微生物,但是根系表面未发现生物;玉米根系分泌物中分布有线虫和生物体,根系表面分布有生物体,其形态与根系分泌物中生物体形态相似。表明此方法是一种原位研究根际生物的较为有效的方法。