Different reactions to adverse neighborhoods in games of cooperation

In social dilemmas, cooperation among randomly interacting individuals is often difficult to achieve. The situation changes if interactions take place in a network where the network structure jointly evolves with the behavioral strategies of the interacting individuals. In particular, cooperation can be stabilized if individuals tend to cut interaction links when facing adverse neighborhoods. Here we consider two different types of reaction to adverse neighborhoods, and all possible mixtures between these reactions. When faced with a gloomy outlook, players can either choose to cut and rewire some of their links to other individuals, or they can migrate to another location and establish new links in the new local neighborhood. We find that in general local rewiring is more favorable for the evolution of cooperation than emigration from adverse neighborhoods. Rewiring helps to maintain the diversity in the degree distribution of players and favors the spontaneous emergence of cooperative clusters. Both properties are known to favor the evolution of cooperation on networks. Interestingly, a mixture of migration and rewiring is even more favorable for the evolution of cooperation than rewiring on its own. While most models only consider a single type of reaction to adverse neighborhoods, the coexistence of several such reactions may actually be an optimal setting for the evolution of cooperation.     

Kefir: a symbiotic yeasts-bacteria community with alleged healthy capabilities

Kefir is a fermented milk beverage. The milk fermentation is achieved by the of kefir grains, a cluster of microorganisms held together by a polysaccharide matrix named kefiran. Kefir grains are an example of symbiosis between yeast and bacteria. They have been used over years to produce kefir, a fermented beverage that is consumed all over the world, although its origin is Caucasian. A vast variety of different species of organisms forming the kefir grains, comprising yeast and bacteria, have been isolated and identified. Kefir is a probiotic food. Probiotics have shown to be beneficial to health, being presently of great interest to the food industry. Kefir has been accredited with antibacterial, antifungal and antitumoural activities among other beneficial attributes. This review includes a critical revision of the microbiological composition of kefir along with its beneficial properties to human health.     

No effect of intraspecific relatedness on public goods cooperation in a complex community

Many organisms—notably microbes—are embedded within complex communities where cooperative behaviors in the form of excreted public goods can benefit other species. Under such circumstances, intraspecific interactions are likely to be less important in driving the evolution of cooperation. We first illustrate this idea with a simple theoretical model, showing that relatedness—the extent to which individuals with the same cooperative alleles interact with each other—has a reduced impact on the evolution of cooperation when public goods are shared between species. We test this empirically using strain of Pseudomonas aeruginosa that vary in their production of metal‐chelating siderophores in copper contaminated compost (an interspecific public good). We show that nonsiderophore producers grow poorly relative to producers under high relatedness, but this cost can be alleviated by the presence of the isogenic producer (low relatedness) and/or the compost microbial community. Hence, relatedness can become unimportant when public goods provide interspecific benefits.     

Oxidative stress and apoptotic events during thermal stress in the symbiotic sea anemone, Anemonia viridis

Symbiosis between cnidarian and photosynthetic protists is widely distributed over temperate and tropical seas. These symbioses can periodically breakdown, a phenomenon known as cnidarian bleaching. This event can be irreversible for some associations subjected to acute and/or prolonged environmental disturbances, and leads to the death of the animal host. During bleaching, oxidative stress has been described previously as acting at molecular level and apoptosis is suggested to be one of the mechanisms involved. We focused our study on the role of apoptosis in bleaching via oxidative stress in the association between the sea anemone Anemonia viridis and the dinoflagellates Symbiodinium species. Characterization of caspase-like enzymes were conducted at the biochemical and molecular level to confirm the presence of a caspase-dependent apoptotic phenomenon in the cnidarian host. We provide evidence of oxidative stress followed by induction of caspase-like activity in animal host cells after an elevated temperature stress, suggesting the concomitant action of these components in bleaching.     

Coevolution of symbiotic mutualists and parasites in a community context

Recent advances in our knowledge of parasitic and mutualistic associations have confirmed the central role of coevolutionary interactions in population and community ecology. Here, we discuss the potential coevolutionary interdependence of the strength and specificity of symbiotic interactions with the complexity and productivity of their environment. We predict that interactions become less beneficial with increasing environmental quality and that the association of productivity with symbiont specificity depends on the relative strengths of tradeoffs between host range and other life-history parameters. However, as biotic complexity increases, pathogen specificity is predicted to decline, whereas mutualist specificity will increase. Testing these predictions on a geographical scale would contribute significantly to the predictive science of coevolution, and to our ability to manage biological interactions embedded in increasingly fragmented landscapes.     

Nutritional approaches to combat oxidative stress in Alzheimer's disease

Alzheimer's disease (AD) brains are characterized by extensive oxidative stress. Additionally, large depositions of amyloid beta-peptide (Abeta) are observed, and many researchers opine that Abeta is central to the pathogenesis of AD. Our laboratory combined these two observations in a comprehensive model for neurodegeneration in AD brains centered around Abeta-induced oxidative stress. Given the oxidative stress in AD and its potentially important role in neurodegeneration, considerable research has been conducted on the use of antioxidants to slow or reverse the pathology and course of AD. One source of antioxidants is the diet. This review examines the literature of the effects of endogenous and exogenous, nutritionally-derived antioxidants in relation to AD. In particular, studies of glutathione and other SH-containing antioxidants, vitamins, and polyphenolic compounds and their use in AD and modulation of Abeta-induced oxidative stress and neurotoxicity are reviewed.     

Metabolic networks to combat oxidative stress in Pseudomonas fluorescens

Oxidative stress is an unavoidable peril that aerobic organisms have to confront. Thus, it is not surprising that intricate strategies are deployed in an effort to fend the dangers associated with living in an O(2) environment. In the classical models of anti-oxidative defense mechanisms, a variety of stratagems including the reactive oxygen species (ROS) scavenging systems, the NADPH-generating enzymes and the DNA repair machineries are highlighted. However, it is becoming increasingly clear that metabolism may be intimately involved in anti-oxidative defence. Recent data show that metabolic reprogramming plays a pivotal role in the survival of organisms exposed to oxidative stress. Here, we describe how Pseudomonas fluorescens, the metabolically-versatile soil microbe, manipulates its metabolic networks in an effort to counter oxidative stress. An intricate link between metabolism and anti-oxidative defense is presented. P. fluorescens reconfigures its metabolic processes in an effort to satisfy its need for NADPH during oxidative insult. Seemingly, disparate metabolic modules appear to partner together to concomitantly fine-tune the levels of the anti-oxidant NADPH and the pro-oxidant NADH. Central to this shift in the metabolic production of the pyridine nucleotides is the increase in NAD kinase with the concomitant decrease in NADP phosphatase. The tricarboxylic acid cycle is tweaked in an effort to limit the formation of NADH. This metabolic redox-balancing act appears to afford a potent tool against oxidative challenge and may be a more widespread ROS-combating tactic than hitherto recognized.     

Zooplankton body size and community structure: Effects of thermal and toxicant stress

Episodic heat waves and an increase in pesticide use are widely cited as consequences of climatic warming. Recent studies show that these stressors often cause declines in the mean body size of zooplankton. Results from laboratory and field studies, as well as observations from both thermal- or toxicant-stressed natural systems, show (1) reductions in mean body size within stressed populations, or (2) changes in community composition that favor small-bodied over large-bodied species. During the past decade, it has become widely accepted that a shift in zooplankton body size can dramatically affect water clarity, rates of nutrient regeneration and fish abundances. Thus, climatic warming and associated change in pesticide use has the potential to cause striking change in the structure and functioning of temperate-zone lakes.     

Renal impairment and analgesia: From effectiveness to adverse effects

Kidney pain is one of the clinically significant features of renal dysfunction. Mild to severe pain is seen in the lower back area. Painkillers are mostly recommended in these cases to relieve the symptom. Yet, several analgesics are associated with side effects that can worsen the state of the disease. This review is based on the studies conducted in these aspects analgesics used to treat kidney pain and their effectiveness, renal consequences of postoperative analgesia, and pharmacogenetics of these palliatives are briefly summarized in this paper.     

Highly diverse community structure in a remote central Tibetan geothermal spring does not display monotonic variation to thermal stress

We report an assessment of whole-community diversity for an extremely isolated geothermal location with considerable phylogenetic and phylogeographic novelty. We further demonstrate, using multiple statistical analyses of sequence data, that the response of community diversity is not monotonic to thermal stress along a gradient of 52-83 degrees C. A combination of domain- and division-specific PCR was used to obtain a broad spectrum of community phylotypes, which were resolved by denaturing gradient gel electrophoresis. Among 58 sequences obtained from microbial mats and streamers, some 95% suggest novel archaeal and bacterial diversity at the species level or higher. Moreover, new phylogeographic and thermally defined lineages among the Cyanobacteria, Chloroflexi, Eubacterium and Thermus are identified. Shannon-Wiener diversity estimates suggest that mats at 63 degrees C supported highest diversity, but when alternate models were applied [Average Taxonomic Distinctness (AvTD) and Variation in Taxonomic Distinctness (VarTD)] that also take into account the phylogenetic relationships between phylotypes, it is evident that greatest taxonomic diversity (AvTD) occurred in streamers at 65-70 degrees C, whereas greatest phylogenetic distance between taxa (VarTD) occurred in streamers of 83 degrees C. All models demonstrated that diversity is not related to thermal stress in a linear fashion.     

mRNPs: From informosomes to stress granules

Eukaryotic cytoplasmic mRNA-containing ribonucleoproteins (mRNPs), which were named informosomes when discovered, have intensely been investigated as various mRNP granules in the past decade. The review considers the structure and functioning of mRNPs. The mRNA status depends on spectrum of RNA-bound proteins and changes in response to signals from signaling pathways.     

Scale invariance of biosystems: From embryo to community

Phenomena having the property of a scale invariance (that is, maintaining invariable structure in certain range of scales) are typical for biosystems of different levels. In this review, main manifestations of the scale-invariant phenomena at different levels of biological organization (including ontogenetic aspects) are stated, and the reasons of such wide distribution of fractal structures in biology are discussed. Almost all biological systems can be described in terms of synergetics as open nonequilibrium systems that exist due to substance and energy flow passing through them. The phenomenon of self-organization is typical for such dissipative systems; maintenance of energy flow requires the existence of complex structures that emerge spontaneously in the presence of the appropriate gradient. Critical systems, which form as a results of their activity scale-invariant structures (that are a kind of distribution channels), are optimal relative to the efficiency of substance and energy distribution. Thus, scale invariance of biological phenomena is a natural consequence of their dissipative nature.     

The effect of thermal stress on Campylobacter coli

AIM: Enteropathogenic Campylobacter jejuni, Camp. coli and Camp. lari are currently the most common cause of acute infectious diarrhoeal illness in the UK. Many domestic animals, including pigs, act as natural reservoirs for these organisms and infection may occur through the ingestion of contaminated foodstuffs. The safety of locally produced porcine liver was assessed in relation to the heat susceptibility of Campylobacter spp. present in eviscerated product. METHODS AND RESULTS: Heat susceptibility (D10) studies were performed on a wild-type strain of Camp. coli [NI39] isolated from porcine liver under standardized conditions. In addition, the effect of culture age and heating menstruum was determined. Thermal stress studies in phosphate-buffered saline showed Camp. coli NI39 to be heat sensitive (D10 = 8.-0, 30.8, 15.6, 10.3 s at 55.4, 57.4, 59.7, 61.2 degrees C, respectively; z = 6.10 degrees C). However, non-logarithmic biphasic survivor curves were observed at higher temperatures ( > 56 degrees C), indicating the presence of a heat-resistant subpopulation (10(4)-10(5) cfu) which was not demonstrated when examining either Salmonella typhimurium or Listeria monocytogenes. CONCLUSIONS: The use of D10 values may be limited. Therefore, porcine liver, under processing, must be treated as a potential source of Campylobacter spp., and clearly defined F-values should be quantified through the use of empirically 'spiked' samples to ensure the eradication of campylobacters from the product, for each individual process being evaluated. SIGNIFICANCE AND IMPACT OF THE STUDY: It is important to define safe processing parameters in the manufacture of products which receive mild thermal processes in order to eliminate the risk of disease to man.     

Adaptation of chickpea to desiccation stress is enhanced by symbiotic rhizobia

This study examined the influence of three inoculant strains of Bradyrhizobium japonicum (Thal-8, Tal 620, Dulawala) on the ability of chickpea (Cicer arietinum (L.) to adapt to drought-stress. Strain Thal-8 was most effective in the root-nodule symbiosis and also partially alleviated decreased growth and yield imposed by drought stress. Strain Thal-8, in pure culture, also produced higher amounts of gibberellic acid (GA) and indole-3-acetic acid (IAA) and lower amounts of abscisic acid (ABA) than the other two test strains. Thal-8 increased the root biomass, GA and IAA contents of leaves of chickpea plants, including ICC 4948NN, a non-nodulating line. These results are consistent with the hypothesis that GA and IAA is produced by the Thal-8 strain and/or elevates levels of these phytohormones in chickpeas. This contributes to its high performance as a nitrogen-fixing microsymbiont. The growth-promoting response evoked by different strains of Bradyrhizobium correlated with higher ratios of GA and IAA relative to ABA phytohormones in the plants.     

From diversity indices to community assembly processes: a test with simulated data

Ecological theory suggests that spatial distribution of biodiversity is strongly driven by community assembly processes. Thus the study of diversity patterns combined with null model testing has become increasingly common to infer assembly processes from observed distributions of diversity indices. However, results in both empirical and simulation studies are inconsistent. The aim of our study is to determine with simulated data which facets of biodiversity, if any, may unravel the processes driving its spatial patterns, and to provide practical considerations about the combination of diversity indices that would produce significant and congruent signals when using null models. The study is based on simulated species’ assemblages that emerge under various landscape structures in a spatially explicit individual‐based model with contrasting, predefined assembly processes. We focus on four assembly processes (species‐sorting, mass effect, neutral dynamics and competition colonization trade‐off) and investigate the emerging species’ distributions with varied diversity indices (alpha, beta and gamma) measured at different spatial scales and for different diversity facets (taxonomic, functional and phylogenetic). We find that 1) the four assembly processes result in distinct spatial distributions of species under any landscape structure, 2) a broad range of diversity indices allows distinguishing between communities driven by different assembly processes, 3) null models provide congruent results only for a small fraction of diversity indices and 4) only a combination of these diversity indices allows identifying the correct assembly processes. Our study supports the inference of assembly processes from patterns of diversity only when different types of indices are combined. It highlights the need to combine phylogenetic, functional and taxonomic diversity indices at multiple spatial scales to effectively infer underlying assembly processes from diversity patterns by illustrating how combination of different indices might help disentangling the complex question of coexistence.     

From ancestral conflicts to local empowerment: two narratives from a Nepalese community

This article concerns the first region that the Maoists declared to be their base area, in the western part of Nepal. It examines how the 10 years of insurrection are reconstructed through two narratives by non-aligned villagers from the same community. These accounts concern two different phases of the conflict. In the first account, the violent irruption of the security forces into the village turned a spotlight on the structural features and historical conditions which made the community vulnerable to the outside intervention, whether by the rebels or by the state. The second narrative illustrates the obverse side of the same community: its capacity to stand up to oppression on the occasion of a Maoist ban on a sacrifice to the local god. The juxtaposition of the two narratives reveals a process of political maturation characterised by a critical analysis of the past and a nascent confidence in the expression of needs and rights.     

From quorum to cooperation: lessons from bacterial sociality for evolutionary theory

The study of cooperation and altruism, almost since its inception, has been carried out without reference to the most numerous, diverse and very possibly most cooperative domain of life on the planet: bacteria. This is starting to change, for good reason. Far from being clonal loners, bacteria are highly social creatures capable of astonishingly complex collective behaviour that is mediated, as it is in colonial insects, by chemical communication. The article discusses recent experiments that explore different facets of current theories of the evolution and maintenance of cooperation using bacterial models. Not only do bacteria hold great promise as experimentally tractable, rapidly evolving systems for testing hypotheses, bacterial experiments have already raised interesting questions about the assumptions on which our current understanding of cooperation and altruism rests.     

Ceramide: From lateral segregation to mechanical stress

Ceramide is a sphingolipid present in eukaryotic cells that laterally segregates into solid domains in model lipid membranes. Imaging has provided a wealth of structural information useful to understand some of the physical properties of these domains. In biological membranes, ceramide is formed on one of the membrane leaflets by enzymatic cleavage of sphyngomyelin. Ceramide, with a smaller head size than its parent compound sphyngomyelin, induces an asymmetric membrane tension and segregates into highly ordered domains that have a much high shear viscosity than that of the surrounding lipids. These physical properties, together with the rapid transmembrane flip-flop of the locally produced ceramide, trigger a sequence of membrane perturbations that could explain the molecular mechanism by which ceramide mediates different cell responses. In this review we will try to establish a connection between the physical membrane transformations in model systems known to occur upon ceramide formation and some physiologically relevant process in which ceramide is known to participate.     

A simplified model to predict stress fracture in young elite combat recruits

The purpose of the study was to develop a simple prediction model for stress fractures (SFs) in young male recruits to identify risk factors for SF. Data were collected from 57 young (18.5 ± 0.5 years) male athletes before elite combat basic training (BT). Measurements included anthropometric variables, blood samples, fitness tests, bone quality (peripheral quantitative computed tomography [pQCT]), psychological assessment, nutritional habits, and history of physical activity. A medical evaluation was done periodically. The SFs were clinically diagnosed during the 1-year training and thereafter confirmed by bone scintigraphy. Three "simple to monitor" variables were found to be significantly (p < 0.05) related to SF occurrence during basic and advanced training: aerobic training frequency, aerobic training duration, and waist circumference. From these 3 variables, a new model was constructed that successfully predicted 85% of the soldiers with (n = 23) and without (n = 34) SF as follows:(Equation is included in full-text article.)where PSF is the stress fracture prediction according to the Log Odds (SF), Odds(SF) is the ratio between the probability of SF existence and nonexistence, ATn is the aerobic training (times per week), ATt is the aerobic training duration (minutes per week), and waist is the circumference (centimeters). This model was validated on a different database taken from another 59 elite combat recruits before BT and successfully predicted 76.5% of the soldiers with SF (n = 22) and without SF (n = 37). A young male recruit for elite combat unit is at a greater risk of developing SF if, before entering BT, he trained aerobically <2 times per week with each training >40 minutes and has a waist circumference of <75 cm. However, further evaluation is required for different combat recruits, ages, and training programs to validate these results.     

Construction of an artificial symbiotic community using a Chlorella-symbiont association as a model.

Chlorella sorokiniana IAM C-212 produces a polysaccharide gel, termed a sheath, under photoautotrophic conditions. The C. sorokiniana sheath is a suitable habitat for several symbiotic microorganisms because it ensures close proximity between the C. sorokiniana and symbionts. In this study, we established a method for increasing the volume of the sheath produced by C. sorokiniana, and proposed a method for constructing artificial communities of Chlorella and symbiotic microorganisms. The C. sorokiniana sheath was increased by addition of calcium chloride solution. The sheath resulted in coflocculation of C. sorokiniana and the associated symbiotic bacteria, thus strengthening the bacterial-Chlorella symbiotic association. An application of this technique was demonstrated by constructing a complex of C. sorokiniana and a propionate-degrading bacterium (PDS1). Although propionate inhibited the growth of axenic C. sorokiniana, the C. sorokiniana-PDS1 complex showed good growth in a medium containing a high concentration of propionate.