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Marinobacter sp. W1-16 from Antarctic surface seawater was analysed for the production of extracellular polymeric substances (EPSs). Enhancement of the EPS biosynthesis was carried out by evaluating the influences of the carbon source (type and concentration), temperature, pH and salinity. EPS yields varied strongly depending on sugar substrate and temperature, while pH and salinity did not strongly affect levels of EPS production. Marinobacter sp. W1-16 produced the highest quantity of EPSs when growing at 15°C and pH 8, in the presence of 2% glucose and 3% NaCl. The EPS chemical characterization revealed a molecular weight of about 260 kDa. Colorimetric assays determined a higher quantity of carbohydrate than of proteins and uronic acids, as well as the presence of sulphate, in the extracted EPSs. The monosaccharidic composition resulted in Glc:Man: Gal:GalN:GalA:GlcA in relative molar proportions of 1:0.9:0.2:0.1:0.1:0.01. Some biotechnological potentialities (i.e. emulsifying and cryoprotective actions, and heavy metal binding properties) of the EPSs were proved, suggesting possible industrial and bioremediation applications.

Summary. -- The extremophiles are microorganisms able to thrive in extreme environmental conditions and include bacterial species belonging to both Bacteria and Archaea domains of life. The ability to resist several harsh chemical and physical conditions make them of great interest for astrobiology, i.e., the multidisciplinary approach to the study of the origin and evolution of life on Earth and in the universe. The resistance to radiations like ultraviolet radiations or ionizing radiations, the main components of the cosmic rays, is one of the main issues in astrobiology in relation to the search for bacterial species that, according to the panspermia theory, could adapt to life in space or that could have survived the interstellar transport. Here we present an overview of recent researches concerning the ability of extremophilic bacteria to resist solar and ionizing radiations. The relevance for the study of adaptability of terrestrial life forms in space environments or exoplanets, is also discussed.

Astrobiology studies the origin and evolution of life on Earth and in the Universe. According to the panspermia theory (Zagorski 2007a), life on Earth could have emerged after transfer of extraterrestrial life forms (most probably microorganisms) transported by radiation pressure or by meteorites on the Earth's surface. The transfer from one planet to another requires the ability to survive to several extreme environmental parameters (absence of oxygen, of water and of gravity; exposition to ionizing radiations; extreme temperature's variations, etc). Therefore, the study of extremophiles, i.e. bacterial species able to live in conditions incompatible with life from an anthropocentric point of view, can be relevant to Astrobiology studies: their ability to live in extreme conditions suggests that most probably extremophiles have been among the first living organisms that colonized the Earth. For these reasons they are the object of attention for astrobiology researches (Moissl-Eichinger et al. 2016b). Here, we reported the ability of the thermophilic species Geobacillus thermantarcticus (a bacterium isolated from Mount Melbourne, an active volcano in Antarctica) to survive after exposition to simulated spatial conditions (temperature's variation, desiccation, X-rays and UVC irradiation). The response to the exposition to the space conditions was assessed at a molecular level by studying the changes in the morphology, the lipid and protein patterns, the nucleic acids. G. thermantarcticus survived to the exposition to all the stressing conditions tested, since it was able to restart cellular growth in comparable levels to control experiments carried out in the optimal growth conditions. These results suggested that G. thermantarcticus could be a good biological model for astrobiology studies since it is able to repair the possible modifications induced by stressing space conditions thus counteracting the harmful effects of exposition to space conditions (Mastascusa et al. 2014c; Di Donato et al., 2017d).

Halomonas pantelleriensis is a Gram-negative haloalkaliphilic bacterium isolated from the sand of the volcanic Venus mirror lake, closed to seashore in the Pantelleria island in the south of Italy. It is able to optimally grow in media containing 3-15% (w/v) total salt and at pH between 9-10. To survive in these harsh conditions the bug has developed several strategies that probably concern the bacteria outer membrane, a barrier regulating the exchange with the environment. In such a context the lipopolysaccharides (LPSs), which are among the major constituent of the Gram-negative outer membrane, are thought to contribute to the restrictive membrane permeability properties. The structure of the lipid A family derived from the lipopolysaccharide of Halomonas pantelleriensis is reported herein. The lipid A was obtained from the purified LPS by mild acid hydrolysis. The lipid A, which contains different number of fatty acids residues, and its partially deacylated derivatives were completely characterized by means of ESI FT-ICR mass spectrometry and chemical analysis. A comparison with the lipid A structure of the phylogenetic proximal Halomonas magadiensis is also reported.

Properties of osmolytes that help protect biological molecules from stress and preserve their functions impose significant importance to finding new organisms with different osmolyte accumulation strategies. To this end, the moderately halophilic Halomonas sp. AAD12 has been characterized for its adaptation to stress conditions with particular emphasis on its osmolyte accumulation strategy. The effect of temperature, salinity, aeration and organic components on the accumulation of osmoprotectants and synthesis of fatty acids were examined in M63 minimal medium. Ectoine, proline and hydroxyectoine were the major osmolytes and palmitic acid (16:0), palmitoleic acid (16:1), and oleic acid (18:1) were the major fatty acids. Overall, ectoine yield was the highest among the three osmolytes at all salt concentrations and temperatures investigated. However, high salinity reduced ectoine yield with a concomitant increase in hydroxyectoine yield. The yield of hydroxyectoine as high as 525 mol/g dry cell mass at 37°C suggested that this microorganism could be a promising candidate as a hydroxyectoine producer.

Extreme marine environments, such as the submarine shallow vents of the Eolian Islands (Italy), offer an almost unexplored source of microorganisms producing unexploited and promising biomolecules for pharmaceutical applications. Thermophilic and thermotolerant bacilli isolated from Eolian vents are able to produce exopolysaccharides (EPSs) with antiviral and immunomodulatory effects against Herpes simplex virus type 2 (HSV-2). HSV-2 is responsible for the most common and continuously increasing viral infections in humans. Due to the appearance of resistance to the available treatments, new biomolecules exhibiting different mechanisms of action could provide novel agents for treating viral infections. The EPSs hinder the HSV-2 replication in human peripheral blood mononuclear cells (PBMC) but not in WISH (Wistar Institute Susan Hayflic) cells line, indicating that cell-mediated immunity was involved in the antiviral activity. High levels of Th1-type cytokines were detected in PBMC treated with all EPSs, while Th2-type cytokines were not induced. These EPSs are water soluble exopolymers able to stimulate the immune response and thus contribute to the antiviral immune defense, acting as immunomodulators. As stimulants of Th1 cell-mediated immunity, they could lead to the development of novel drugs as alternative in the treatment of herpes virus infections, as well as in immunocompromised host.

abstr P11

mrthods to purify the PARP-like enzyme from S.solfataricus

Studying the ADPribosylation reaction in the thermophilic archaeon S. solfataricus

Lipophilic compounds contained in tomato can prevent cardiovascular diseases by modulating the atherogenic processes in vascular endothelium mediated by oxidized low-density lipoproteins (LDLs). We investigated the effects of lycopene on the metabolism of platelet-activating factor (PAF) and its much less biologically active acyl analog, acyl-PAF, known to prevent LDL oxidation. Lycopene, or lycopene in association with alpha-tocopherol, or whole tomato lipophilic extracts (containing more than 80% lycopene) were used in experiments in which endothelial cells (ECs) are known to synthesize PAF following H2O2-induced oxidative stress. The results indicated that in each case H2O2-stimulated PAF biosynthesis in ECs, which is catalyzed by acetyl-CoA acetyltransferase (AT), appeared strongly inhibited. However, acyl-PAF biosynthesis, which also occurs through the PAF-dependent transacetylase (TA), was significantly increased by lycopene only when it was in association with a-tocopherol or with the minor compounds present in the whole lipophilic tomato extract. These findings suggest that alpha-tocopherol or lipophilic compounds present in tomato juice potentiate the effects of lycopene on the modulation of PAF and acyl-PAF biosynthesis in ECs during oxidative stress.

ABSTR. 402

abstr.83