Andrea Colacevich

Antimicrobial activity against Helicobacter pylori strains and antioxidant properties of blackberry leaves (Rubus ulmifolius) and isolated compounds

Rubus spp. (Rosaceae) provide extracts used in traditional medicine as antimicrobial, anticonvulsant, muscle relaxant and radical scavenging agents. Resistance to antibiotics used to treat Helicobacter pylori infection as well as their poor availability in developing countries prompted us to test the antimicrobial activity of Rubus ulmifolius leaves and isolated polyphenols against two H. pylori strains with different virulence (CagA+ strain 10K and CagA(-) strain G21). The antioxidant activity (TEAC values) of the tested compounds ranged from 4.88 (gallic acid) to 1.60 (kaempferol), whilst the leaf extract gave a value of 0.12. All the isolated polyphenols as well as the leaf extract showed antibacterial activity against both of the H. pylori strains. The minimum bactericidal concentrations (MBCs) of the extract for H. pylori strains G21 and 10K, respectively, were 1200 microg/mL and 1500 microg/mL after 24h of exposure and 134 microg/mL and 270 microg/mL after 48 h exposure. Ellagic acid showed very low MBC values towards both of the H. pylori strains after 48 h (2 microg/mL and 10 microg/mL for strains G21 and 10K, respectively) and kaempferol toward G21 strain (MBC=6 microg/mL). A relationship between antimicrobial activity and antioxidant capacity was found only for H. pylori strain G21 CagA(-) strain.

Temporal variation in the water chemistry of northern Victoria Land lakes (Antarctica)

Abstract.Concentrations of major ions, silicate and nutrients (total N and P) were measured in samples of surface water from 28 lakes in ice-free areas of northern Victoria Land (East Antarctica). Sixteen lakes were sampled during austral summers 2001/02, 2003/04, 2004/05 and 2005/06 to assess temporal variation in water chemistry. Although samples showed a wide range in ion concentrations, their composition mainly reflected that of seawater. In general, as the distance from the sea increased, the input of elements from the marine environment (through aerosols and seabirds) decreased and there was an increase in nitrate and sulfate concentrations. Antarctic lakes lack outflows and during the austral summer the melting and/or ablation of ice cover, water evaporation and leaching processes in dry soils determine a progressive increase in water ion concentrations. During the five-year monitoring survey, no statistically significant variation in the water chemistry were detected, except for a slight (hardly significant) increase in TN concentrations. However, Canonical Correspondence Analysis (CCA) indicated that other factors besides distance from the sea, the presence of nesting seabirds, the sampling time and percentage of ice cover affect the composition of water in Antarctic cold desert environments.

The microalgae Tetraselmis suecica in mesocosms under different light regimes

Pigment profiles and pheopigment accumulation of the microalga Tetraselmis suecica were studied under different spectral irradiances. Irradiance conditions typical of coastal waters with (‘clear’) and without (‘coloured’) chromophoric dissolved organic matter (C-DOM) were simulated in mesocosm cultures. The lag, growth and stationary phases were found to follow a logistic model, as light limitation controlled growth where maximum carrying capacity and incremental growth were sensitive to irradiance conditions, both being higher in mesocosms with full irradiance conditions (clear sea conditions without attenuation due to C-DOM). Through daily measurements of chlorophylls, carotenoids and pheopigments, it was found that the highest concentrations of pigments occurred in the growth phase: in particular in the clear sea conditions. Lower concentrations of lutein were measured in the coloured mesocosms showing their protective function against photo-oxidation. Pheopigment concentrations increased linearly throughout the experiment, being highest in the mesocosm with clear sea conditions. In general, clear sea conditions, including ultraviolet irradiance, showed the higher production of primary and secondary pigments, demonstrating the high tolerability of T. suecica to a range of solar irradiance conditions.

Water geochemistry and sedimentary pigments in northern Victoria Land lakes, Antarctica

Total concentrations of algal pigments, organic C, C, N, P and S were determined in surface sediments from the littoral zone of 21 lakes in ice-free areas of northern Victoria Land (Antarctica) with different climatic and environmental conditions. Concentrations of major ions and nutrients were also determined in water samples from the same lakes. The latter samples had extremely variable chemical compositions; however, all the lakes resulted oligotrophic. Pigment concentrations in surface sediments were comparable to those reported for other Antarctic lakes and lower than those in oligotrophic lakes at lower latitudes. Cyanophyta, Chlorophyta and Bacillariophyta were the main taxa identified. These taxa correspond to those reported in previous microscopy-based studies on Antarctic phytoplankton and phytobenthos. Discriminant Function Analysis and Canonical Correspondence Analysis of data indicate that the distribution of pigments in these Victoria Land lakes depends mainly on their geographical location (particularly the distance from the sea) and nutrient status.

An Update on Sedimentary Pigments in Victoria Land Lakes (East Antarctica)

Abstract Antarctic ice-free areas contain lakes and ponds that have interesting limnological features and are of wide global significance as early warning indicators of climatic and environmental change. However, most limnological and paleolimnological studies in continental Antarctica are limited to certain regions. There are several ice-free areas in Victoria Land that have not yet been studied well. There is therefore a need to extend limnological studies in space and time to understand how different geological and climatic features affect the composition and biological activity of freshwater communities. With the aim of contributing to a better limnological characterization of Victoria Land, this paper reports data on sedimentary pigments (used to identify the main algal taxa) obtained through a methodology that is more sensitive and selective than that of previous studies. Analyses were extended to 48 water bodies in ice-free areas with differing lithology, latitude, and altitude, and with different morphometry and physical, chemical, and biological characteristics in order to identify environmental factors affecting the distribution and composition of freshwater autotrophic communities. A wider knowledge of lakes in a limnologically important region of Antarctica was obtained. Cyanophyta was found to be the most important algal group, followed by Chlorophyta and Bacillariophyta, whereas latitude and altitude are the main factors affecting pigment distribution.

Algal biomass and pigments along a latitudinal gradient in Victoria Land lakes, East Antarctica

It is generally accepted that Antarctic terrestrial diversity decreases as latitude increases, but latitudinal patterns of several organisms are not always as clear as expected. The Victoria Land region is rich in lakes and ponds and spans 8 degrees of latitude that encompasses gradients in factors such as solar radiation, temperature, ice cover and day length. An understanding of the links between latitudinally driven environmental and biodiversity changes is essential to the understanding of the ecology and evolution of Antarctic biota and the formulation of hypotheses about likely future changes in biodiversity. As several studies have demonstrated that photosynthetic pigments are an excellent, although underused, tool for the study of lacustrine algal communities, the aim of the present study was to investigate variations in algal biomass and biodiversity across the latitudinal gradient of Victoria Land using sedimentary pigments. We test the hypothesis that the biodiversity of freshwater environments decreases as latitude increases. On the basis of our results, we propose using the number of sedimentary pigments as a proxy for algal diversity and the sum of chlorophyll a and bacteriochlorophyll a with their degradation derivatives as an index of biomass. Overall, our data show that biomass and diversity decrease as latitude increases but local environmental conditions, in particular, natural levels of eutrophy, can affect both productivity and diversity.