Facultative virulence: A strategy to manipulate host behaviour?

Examples of behavioural manipulation by parasites are numerous, but the processes underlying these changes are not well characterized. From an evolutionary point of view, behavioural changes in infected hosts have often been interpreted as illustrations of the extended phenotype concept, in which genes in one organism (the parasite) have phenotypic effects on another organism (the host). Here, we approach the problem differently, suggesting that hosts, by cooperating with manipulative parasites rather than resisting them, might mitigate fitness costs associated with manipulation. By imposing extra fitness costs on their hosts in the absence of compliance, parasites theoretically have the potential to select for cooperative behaviour by their hosts. Although this 'mafia-like' strategy remains poorly documented, we believe that it has substantial potential to resolve issues specific to the evolution of behavioural alterations induced by parasites.     

Influence of environmental conditions on putisolvins I and II production in Pseudomonas putida strain PCL1445

Pseudomonas putida strain PCL1445 produces the cyclic lipopeptides putisolvin I and II, which are biosurfactants affecting environmentally important functions including swarming motility, solubility of nutrients and biofilm formation and maintenance. In this study, the effect of relevant nutritional and environmental factors on putisolvin production by PCL1445 was analyzed. Growth and levels of putisolvins I and II biosynthesis were significantly influenced by various carbon sources and by the nature of amino acid supplemented to the culture medium. An increase in the salt concentration of BM medium as well as growth at 1% oxygen significantly increased putisolvin production. In addition, we recently demonstrated that growth at a low temperature has a positive effect on putisolvin production. Analysis of the expression of gacA and gacS in Tn5luxAB mutant strains at a low temperature or under a high salt concentration suggests that biosynthesis of putisolvin is modulated through the GacA/GacS two-component regulatory system in PCL1445 under the tested conditions.     

A rice calcium- and calmodulin-dependent protein kinase restores nodulation to a legume mutant

The Medicago truncatula DMI3 gene encodes a calcium- and calmodulin-dependent protein kinase (CCaMK) that is necessary for the establishment of both rhizobial and mycorrhizal symbioses. The two symbiotic signaling pathways diverge downstream of DMI3; therefore, it has been proposed that legumes have evolved a particular form of CCaMK, acting like a switch able both to discriminate between rhizobial and mycorrhizal calcium signatures and to trigger the appropriate downstream signaling pathway. To test this hypothesis, we examined whether a CCaMK gene from a nonlegume species was able to restore the rhizobial symbiotic properties of a M. truncatula dmi3 mutant. Our results show that a CCaMK gene from rice can restore nodule formation, indicating that CCaMKs from nonlegumes can interpret the calcium signature elicited by rhizobial Nod factors and activate the appropriate downstream target. The nodules did not contain bacteria, which suggests that DMI3 is also involved in the control of the infection process.     

Influence of substratum on the degradation processes in diesel polluted sub-Antarctic soils (Crozet Archipelago)

Biodegradation by naturally occurring populations of microorganisms is a major mechanism for the removal of oil hydrocarbons from the environment. Therefore, follow-up of bacterial populations and chemical indices of biodegradation are important components of contaminated site assessment studies. Over a 4-year period following an accidental diesel contamination of the sub-Antarctic Crozet Archipelago (51°51′E–46°25′S), a field study was carried out in the contaminated area that is located in a transition zone between an arid fell-field (upstream) and a wet vegetated area (downstream). This study included a monitoring of heterotrophic and hydrocarbon-degrading bacterial abundance and chemical analysis of the remaining hydrocarbons. Significant higher number of heterotrophic and hydrocarbon-degrading bacterial counts revealed a rapid acclimation of sub-Antarctic microbial soil communities to the diesel fuel contamination. A chemical survey conducted during the last 2 years (2002 and 2003) showed that the total extractable hydrocarbons (TPH) content in arid fell field was reduced to ≤50% of their value while it was reduced only to ≤65% in vegetated soil. In addition, the decrease of TPH was always higher in the presence of fertilizer in the arid contaminated area, while fertilizer addition was almost inefficient in the wet contaminated one. All these results demonstrate a serious influence of the soil properties on the degradation rate. However, all chemical indices showed a significant reduction of alkanes and light aromatics in both contaminated area confirming a regular oil degradation process.     

Life-span in generations of chronic irradiated Drosophila wild type isogenic and geterogenic strains

With the goal to study radioadaptation on life-span and observe the role in this phenomenon of genotype, we investigated the dynamics of life-span in 14 consistent generations after chronic gamma-irradiation in heterogenic (Canton-S) and isogenic (Oregon-R spa) Drosophila wild type strains. The gamma-source was 226Ra in dose 60 cGy per generation. The animals kept in standard conditions (25 degrees C and 12 h lighting). Was shown, that the dynamics of median life-span in wild type strains Canton-S and Oregon-R spa was different and the character of alterations depends on genetic heterogeneity. After chronic irradiation in generations in heterogenic line Canton-S since 5 generation cyclic life-span oscillations disappeared, values of median life-span leave on a plateau. Since the 8th generation the life-span values of irradiated populations exceeded all the control values. As a result of the irradiation practically in all generations in isogenic line Oregon-R spa occurs increasing of life-span with the comparing to non-irradiated control. This is possible due to the positive influence of radio-induced heterogeneity on the life-span of isogenic strain. Thus, chronic irradiation led to violation of natural cyclic dynamics of Drosophila life-span in heterogenic strain, discovered in the end 80-s' years by F. Lints and D. Ismaylov. Irradiation of isogenic strain led to increasing of life-span in all generations.     

Genetic aspects of the irradiation in small doses of laboratory lines and experimental populations Drosophila melanogaster

One of explanations of revealed effects of small doses of an irradiation is induced genetic instability on which background there is a realization of the various radiobiological reactions resulting as to stimulation, and significant oppression of the vital functions of a cell or an organism. In work the given estimations of consequences of an irradiation in small doses of mutant lines of the drosophila are submitted. Paramount value in definition of their size and an orientation of reaction of a genotype is supposed, that, have processes leaders to change of activity of mobile genetic elements and programmed destruction of a cell.     

Lipid oxidation and autophagy in yeast

Autophagy, a process involved in the degradation and the recycling of long-lived proteins and organelles to survive nitrogen starvation, is generally non-selective. However, recent data suggest that selective forms of autophagy exist, that are able to specifically target several organelles, including mitochondria. Conversely, mitochondrial alterations could trigger autophagy. Such a selective form of autophagy might be involved in the elimination of damaged mitochondria. We reported previously that, mitochondria were early targets of rapamycin-induced autophagy. Here we report that rapamycin-induced autophagy is accompanied by the early production of reactive oxygen species and by the early oxidation of mitochondrial lipid. Inhibition of these oxidative effects by resveratrol largely impaired autophagy of both cytosolic proteins and mitochondria, and delayed subsequent cell death. These results support a role of mitochondrial oxidation events in the activation of autophagy.     

Model-free model elimination: A new step in the model-free dynamic analysis of NMR relaxation data

Model-free analysis is a technique commonly used within the field of NMR spectroscopy to extract atomic resolution, interpretable dynamic information on multiple timescales from the R ₁, R ₂, and steady state NOE. Model-free approaches employ two disparate areas of data analysis, the discipline of mathematical optimisation, specifically the minimisation of a χ² function, and the statistical field of model selection. By searching through a large number of model-free minimisations, which were setup using synthetic relaxation data whereby the true underlying dynamics is known, certain model-free models have been identified to, at times, fail. This has been characterised as either the internal correlation times, τ _e , τ _f , or τ _s , or the global correlation time parameter, local τ _m , heading towards infinity, the result being that the final parameter values are far from the true values. In a number of cases the minimised χ² value of the failed model is significantly lower than that of all other models and, hence, will be the model which is chosen by model selection techniques. If these models are not removed prior to model selection the final model-free results could be far from the truth. By implementing a series of empirical rules involving inequalities these models can be specifically isolated and removed. Model-free analysis should therefore consist of three distinct steps: model-free minimisation, model-free model elimination, and finally model-free model selection. Failure has also been identified to affect the individual Monte Carlo simulations used within error analysis. Each simulation involves an independent randomised relaxation data set and model-free minimisation, thus simulations suffer from exactly the same types of failure as model-free models. Therefore, to prevent these outliers from causing a significant overestimation of the errors the failed Monte Carlo simulations need to be culled prior to calculating the parameter standard deviations.     

In vivo oxidation of [9-14C] cyclic fatty acids derived from linolenic acid in the rat

Heating oils and fats may lead to cyclization of polyunsaturated fatty acids, as for example linolenic acid. Cyclohexenyl and cyclopentenyl fatty acids are subsequently present in some edible oils and these are suspected to induce metabolic disorders. In a previous experiment using [1-14C] labeled molecules, we published that these cyclic fatty acids are beta oxidized to the same extent as linolenic acid, at least for the first cycle of beta oxidation. However, it is possible that the presence of a ring could alter the ability of the organism to fully oxidize the molecule. In order to test this hypothesis, we assessed the oxidative metabolism of cyclic fatty acids carrying a 14C atom at the vicinity of the ring. For this purpose, rats were force-fed from 1.1 to 1.3 MBq of a representative fraction of dietary cyclohexenyl cyclic fatty acid monomers of [9-14C] 9-(6-propyl-cyclohex-3-enyl)-non-8-enoic acids and 14CO2 production was monitored for 24h. The animals were then necropsied and the radioactivity was determined in different tissues. No consistent radioactivity was recovered as 14CO2 24h after administration of the molecules. Sixty percent of the radioactivity was recovered in the urine and 30% in the gastrointestinal tract. By combining our previous data on the oxidation of [1-14C] cyclic fatty acids and the present results, we suggest that cyclohexenyl fatty acids are first beta oxidized in a similar way as linolenic acid and that the remaining molecule carrying the ring is detoxified and eliminated in the urine and feces.