Changes in the non-protein thiol pool and production of dissolved gaseous mercury in the marine diatom Thalassiosira weissflogii under mercury exposure

Two detoxification mechanisms working in the marine diatom Thalassiosira weissflogii to cope with mercury toxicity were investigated. Initially, the effect of mercury on the intracellular pool of non-protein thiols was studied in exponentially growing cultures exposed to sub-toxic HgCl(2) concentrations. T. weissflogii cells responded by synthesizing metal-binding peptides, named phytochelatins (PCs), besides increasing the intracellular pool of glutathione and gamma-glutamylcysteine (gamma-EC). Intracellular Hg and PC concentrations increased with the Hg concentration in the culture medium, exhibiting a distinct dose-response relationship. However, considerations of the PCs-SH:Hg molar ratio suggest that glutathione could also be involved in the intracellular mercury sequestration. The time course of the non-protein thiol pool and Hg intracellular concentration shows that PCs, glutathione and gamma-EC represent a rapid cellular response to mercury, although their role in Hg detoxification seems to lose importance at longer incubation times. The occurrence of a process of reduction of Hg(II) to Hg degrees and subsequent production of dissolved gaseous mercury (DGM) was also investigated at lower Hg concentrations, at which the PC synthesis doesn't seem to be involved. The significant (P<0.01) correlation between the cellular density in solution and the production of DGM suggests that this diatom is capable of directly producing DGM, both in light and dark conditions. This finding has been confirmed by the absence of DGM production in the culture media containing formaldehyde-killed cells. Finally, the relationship between these two different pathways of Hg detoxification is discussed.

Characterization of the pheromone gene family of an Antarctic and Arctic protozoan ciliate, Euplotes nobilii

Allelic genes encoding water-borne signal proteins (pheromones) were amplified and sequenced from the somatic (macronuclear) sub-chromosomic genome of Antarctic and Arctic strains of the marine ciliate, Euplotes nobilii. Their open reading frames appeared to be specific for polypeptide sequences of 83 to 94 amino acids identifiable with cytoplasmic pheromone precursors (pre-pro-pheromones), requiring two proteolytic steps to remove the pre- and pro-segments and secrete the mature pheromones. Differently from most of the macronuclear genes that have so far been characterized from Euplotes and other hypotrich ciliates, the 5' and 3' non-coding regions of all the seven E. nobilii pheromone genes are much longer than the coding regions (621 to 700 versus 214 to 285 nucleotides), and the 5' regions in particular show nearly identical sequences across the whole set of pheromone genes. These structural peculiarities of the non-coding regions are likely due to the presence of intron sequences and provide presumptive evidence that they are site of basic, conserved activities in the mechanism that regulates the expression of the E. nobilii pheromone genes.

Dissolved gaseous mercury production in the dark: Evidence for the fundamental role of bacteria in different types of Mediterranean water bodies

It is well established that the dissolved gaseous mercury (DGM) production in waters is mainly driven by photochemical processes. The present paper provides evidence for a significant bacteria-mediated DGM production, occurring also under dark conditions in environmentally different types of coastal water bodies of the Mediterranean basin. The DGM production was laboratory determined in sea, lagoon-brackish and lake water samples, comparing the efficiency of the DGM production processes in darkness and in the light. This latter condition was established by exposing samples at solar radiation intensity in the Photosyntetical Active Radiation region (PAR) of 200 W m(-2). Mercury reduction rate in the dark was of the order of 2-4% of the DGM production in lightness, depending on the total mercury concentration in the water, rather than the bacterial abundance in it. Support for the active bacterial role in mercury reduction rate under dark conditions was provided by: 1) absence of significant DGM production in sterilized water samples (following filtration treatment or autoclaving), 2) restored DGM production efficiency, following re-inoculation into the same water samples of representatives of their bacterial community, previously isolated and separately cultured. Notwithstanding the low bacteria-mediated vs. the high photo-induced DGM production, whatever natural water body was considered, it is worth stressing the significant contribution of this organismal-mediated process to oceanic mercury evasion, since it occurs continuously along the entire water column throughout the 24 h of the day.

Action mechanisms of the secondary metabolite euplotin C: signaling and functional role in Euplotes

Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca(2+) and Na(+), suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment.

Effect of the bioactive metabolite euplotin C on phagocytosis and fluid-phase endocytosis in the single-celled eukaryote Paramecium

The effect of euplotin C -- a lipophilic bioactive metabolite produced by the ciliate Euplotes crassus -- on the kinetics of both phagocytosis of latex particles and fluid-phase uptake of dextran, was studied in the single-cell ciliate Paramecium primaurelia. The inhibition of food vacuole formation was concentration- and time-dependent (p<0.001), even if euplotin C did not completely block the phagocytosis. Following a 15 min treatment with a euplotin C (0.5 microg/ml), the latex particle uptake was inhibited up to 25%. Furthermore, the pretreatment of cells with taxol strongly counteracted euplotin C effect. The amount of extracellularly provided dextran, which is internalized exclusively by fluid-phase uptake, was quantified in cells whose phagocytic activity was blocked by trifluoperazine. The amount of the internalized dextran was about 50% of that in controls after 15 min incubation in the presence of euplotin C. Fluorescence confocal images showed that no endosomes were formed on the surface of these cells. The effect of euplotin C on the food vacuole formation and fluid-phase endocytosis is apparently mediated by a modification of microtubule network.

[Silica risk in construction industry: an investigation on raw materials]

Typical construction activities like demolition, excavation and sanding can expose workers to silica, but there are few investigations carried out with the aim of evaluating the silica content in raw materials used for these activities (mortars, plasters, cement...). Our intervention has been directed in looking for free crystalline silica in samples of raw materials. We have measured the silica content in these materials comparing declared and real composition found in the products. Our intent was to obtain more information about the working activities which expose workers to free crystalline silica in construction industry and to highlight the silica presence in raw materials also when the companies don't declare it, against labeling rules based on Italian law D.lgs 65/03.

[Emerging problems in enforcement of safe maternity and feeding protection at work: a public prevention service experience]

We have examined the claims for advance maternity leave or prolonged benefits for breastfeeding addressed to Occupational Health Unity of Local Health Service 11 by women at harmful works in the period 2002-2005. The most frequent occupations were: shoemaker (29%), service company's employee (7%), tanners (7%), leather industry's employee (6%) and food industry's employee (6%). The most important risk factors were: bound postures, manual load handling, chemical hazards and biological agents. The numbers of claims increased during the period of interest. In the work place often risks for pregnancy and breastfeeding are not correctly assessed and women workers are not informed on their rights. The Occupational Health Unity of Local Health Service 11 tried to correct the lack of information for workers, employers, workers' representatives in health and safety and enterprise's occupational health physician.

Lack of genetic structure of Cypriot Alectoris chukar (Aves, Galliformes) populations as inferred from mtDNA sequencing data

The Chukar (Alectoris chukar cypriotes) is the most common game bird in Cyprus. Since 1990 the Cypriot Government has established a restocking program with captive-reared birds. However, this program has not been guaranteed by checking the genetic nature of wild and farmed samples, either in the areas controlled by the Cypriot Government or in northern Cyprus. The sequencing of both Cytochrome-b and Control Region of the mitochondrial DNA was carried out for 61 Cypriot representatives and 14 specimens of the same subspecies from Crete and Israel. Only the A. chukar maternal lineage was found. A partitioning of Cypriot specimens among different clades was not reliably supported, whereas robust bootstrap values weighted for an evolutionary divergence between Cypriot and Cretan Chukars. An overall genetic homogeny of the Cypriot populations was disclosed, whatever their status (captive vs. wild stocks) and origin (Government controlled vs. occupied areas) would be, a higher nucleotide diversity of the wild vs. captive representatives notwithstanding.

Molecular mechanisms of euplotin C-induced apoptosis: involvement of mitochondrial dysfunction, oxidative stress and proteases

The metabolite euplotin C (EC), isolated from the marine ciliate Euplotes crassus, is a powerful cytotoxic and pro-apoptotic agent in tumour cell lines. For instance, EC induces the rapid depletion of ryanodine Ca(2+) stores, the release of cytochrome c from the mitochondria, and the activation of caspase-3, leading to apoptosis. The purpose of this study was to gain further insight into the mechanisms of EC-induced apoptosis in rat pheochromocytoma PC12 cells. We found that EC increases Bax/Bcl-2 ratio and that Bax is responsible of the EC-induced dissipation of the mitochondrial membrane potential (Deltapsi(m)). In addition, EC induces the generation of reactive oxygene species (ROS) without involvement of p53. The inhibition of ROS generation prevents, at least in part, the pro-apoptotic effects of EC as well as the effects of EC on Bax, Deltapsi(m) and intracellular free Ca(2+), indicating a cross-talk between different pathways. However, definition of the effector cascade turns out to be more complex than expected and caspase-independent mechanisms, acting in parallel with caspases, should also be considered. Among them, EC increases the expression/activity of calpains downstream of ROS generation, although calpains seem to exert protective effects.

Genetic insight into Mediterranean chukar (Alectoris chukar, Galliformes) populations inferred from mitochondrial DNA and RAPD markers

The chukar (Alectoris chukar, Galliformes) is one of the most important game birds as it is widely distributed and hunted over the whole of its range. The aim of this work was to assess the genetic differentiation as well as the possible presence of hybrid specimens in A. chukar populations from Italy, Greece and Cyprus. To provide phylogenetic context, conspecific, allopatric specimens from Israel, Georgia, Armenia, Kazakhstan, Afghanistan, Pakistan, Mongolia, China and USA were compared. Sequencing of the mitochondrial DNA (mtDNA) Control Region supplied information on the ancestry of A. chukar populations, whereas Random Amplified Polymorphic DNA (RAPD) fingerprinting was used to assess whether hybridization had occurred. The Italian population was found to be an inter-specific mixture of A. chukar and A. rufa (i.e., the red-legged partridge) mtDNA lineages, whereas the representatives from Greece and Cyprus showed only the A. chukar maternal line. RAPD markers revealed introgression with A. rufa genes in the Italian population, whereas no A. chukar x A. rufa hybrid specimens were detected in the eastern Mediterranean populations. The genetic data obtained from the Italian A. chukar population as well as from a few Greek specimens pointed against their Mediterranean kinship, suggesting relationships with A. chukar subspecies from the easternmost part of the Asian continent.

Cytotoxic effects and apoptotic signalling mechanisms of the sesquiterpenoid euplotin C, a secondary metabolite of the marine ciliate Euplotes crassus, in tumour cells

Most antitumour agents with cytotoxic properties induce apoptosis. The lipophilic compound euplotin C, isolated from the ciliate Euplotes crassus, is toxic to a number of different opportunistic or pathogenic microorganisms, although its mechanism of action is currently unknown. We report here that euplotin C is a powerful cytotoxic and pro-apoptotic agent in mouse AtT-20 and rat PC12 tumour-derived cell lines. In addition, we provide evidence that euplotin C treatment results in rapid activation of ryanodine receptors, depletion of Ca2+ stores in the endoplasmic reticulum (ER), the release of cytochrome c from the mitochondria, activation of caspase-12, and activation of caspase-3, leading to apoptosis. Intracellular Ca2+ overload is an early event which induces apoptosis and is parallelled by ER stress and the release of cytochrome c, whereas caspase-12 may be activated by euplotin C at a later stage in the apoptosis pathway. These events, either independently or concomitantly, lead to the activation of the caspase-3 and its downstream effectors, triggering the cell to undergo apoptosis. These results demonstrate that euplotin C may be considered for the design of cytotoxic and pro-apoptotic new drugs.

Antimicrobial activity of euplotin C, the sesquiterpene taxonomic marker from the marine ciliate Euplotes crassus

Strains of the marine ciliate protist Euplotes crassus produce exclusive terpenoids called euplotins that play an ecological role. Among these derivatives, euplotin C is the main of four secondary metabolites isolated from cultures of this protozoon and represents the sesquiterpene taxonomic marker from E. crassus. Because different terpenoid metabolites of plant origin showed a certain antimicrobial activity, we assessed the compound euplotin C, purified by high-pressure liquid chromatography and solubilized in two solubility enhancers, against the protozoa Leishmania major and Leishmani infantum, the fungus Candida albicans, and nine strains of gram-positive and gram-negative microorganisms. An activity of euplotin C against Leishmania promastigotes was demonstrated (50% lethal doses were 4.6 or 8.1 microg/ml depending on the agent used to solubilize the compound), while the effect was less evident on Candida and nearly absent on bacteria. A nonsignificant cytotoxicity (50% lethal dose, >200 microg/ml) against the J774 cell line was observed. A leishmanicidal activity was also shown by the living, euplotin-producing cells of E. crassus cultured together with promastigotes; this activity increased with time from 10 min to 6 h of incubation. This study provides an initial rationale for the evaluation of euplotin C and other similar natural products as alternative or possibly synergistic compounds for current antiprotozoon chemotherapeutics.

Importance of the biogenic organic matter in photo-formation of dissolved gaseous mercury in a culture of the marine diatom Chaetoceros sp

Laboratory experiments on DGM production under light/dark cycles in a culture of the marine diatom Chaetoceros sp. spiked with 200 ng l(-1) of mercury have been performed. DGM formation has been investigated also in the cell exudates, obtained by filtration of the cell culture. Results show that the cell culture and the filtrate give the same value of DGM production (2.24+/-0.88 pg min(-1) l(-1) and 2.23+/-0.02 pg min(-1) l(-1), respectively) in the light (40 W m(-2)), values much higher than to those obtained in the medium culture alone. A significant DGM production has been measured in dark conditions both in the cell culture (0.48+/-0.11 pg min(-1) l(-1)) and in the filtrate (0.85+/-0.10 pg min(-1) l(-1)). The results highlight that the organic compounds released by the cell in the culture medium play a fundamental role in the DGM photo-formation processes.

In situ identification by fluorescently labeled oligonucleotide probes of morphologically similar, closely related ciliate species

Ciliate protozoa are important members of microbial communities in which they play specific ecological roles. The determination of single species distribution is fundamental for food web analysis, but species recognition, which is mainly based on morphological characters, is often difficult between closely related species. The use of species-specific, purposely designed, fluorescently labeled probes for in situ hybridization is here presented as an easy and fast identification method for three closely related species belonging to the widespread genus Euplotes, namely E. crassus, E. vannus, and E. minuta, that in spite of their remarkable morphological similarity have significant metabolic and ecological differences. These three species can be detected simultaneously, provided the probes employed are bound to different fluorescent dyes: in this way their relative abundance and their population dynamics in the natural environment can be evaluated. As more ciliate sequences become available in databases, species-specific probes can be designed for other ciliates, thus rendering the application of the method of more general importance. The probes used in this study may also provide a tool to prevent erroneous species identification in future studies.

Ethogram of Aspidisca sedigita

The analysis of behaviour of Aspidisca sedigita has been undertaken to describe the main features of its biology. In drawing the standard ethogram of A. sedigita, several peculiarities have been discovered: (i) the cirri of Aspidisca are thicker and tufted versus the slim and pointed cirri of other hypotrichs; (ii) the side-stepping reaction is performed without its typical backward motion; (iii) a typical clockwise rotation of 90°, followed by a similar but anticlockwise one, is performed frequently and results in a shift of the creeping Aspidisca into a new trajectory, close and parallel to the previous one; (iv) the very rare swimming motion of the species occurs along a regular helicoid, with the ciliary organelles facing in the opposite direction of the centre of the helicoid; (v) the creeping and swimming of conjugating pairs are similar to those of single organisms. The analysis of behaviour of A. sedigita is suggested to contribute to our knowledge of the adaptive strategies of this species.