M. Volterrani

Arsenic-resistant bacteria isolated from contaminated sediments of the Orbetello Lagoon, Italy, and their characterization.

Aims:  The aim of this study was to isolate arsenic‐resistant bacteria from contaminated sediment of the Orbetello Lagoon, Italy, to characterize isolates for As(III), As(V), heavy metals resistance, and from the phylogenetic point of view.

Two naphthalene degrading bacteria belonging to the genera Paenibacillus and Pseudomonas isolated from a highly polluted lagoon perform different sensitivities to the organic and heavy metal contaminants

Two bacterial strains were isolated in the presence of naphthalene as the sole carbon and energy source from sediments of the Orbetello Lagoon, Italy, which is highly contaminated with both organic compounds and metals. 16S rRNA gene sequence analysis of the two isolates assigned the strains to the genera Paenibacillus and Pseudomonas. The effect of different contaminants on the growth behaviors of the two strains was investigated. Pseudomonas sp. ORNaP2 showed a higher tolerance to benzene, toluene, and ethylbenzene than Paenibacillus sp. ORNaP1. In addition, the toxicity of heavy metals potentially present as co-pollutants in the investigated site was tested. Here, strain Paenibacillus sp. ORNaP1 showed a higher tolerance towards arsenic, cadmium, and lead, whereas it was far more sensitive towards mercury than strain Pseudomonas sp. ORNaP2. These differences between the Gram-negative Pseudomonas and the Gram-positive Paenibacillus strain can be explained by different general adaptive response systems present in the two bacteria.

Assessment of environmental pollutants in ten southern Italy harbor sediments.

In 2003–2006, the distribution of macronutrients and pollutants of environmental interest was investigated in surficial sediments collected from 10 southern Italy harbors selected in four different regions. About 167 stations were sampled to determine levels of total organic carbon, total nitrogen, total phosphorous, trace elements (Al, Cd, Pb, Ni, Cr, Cu, Zn, Hg, As), short- and long-chain aliphatic hydrocarbons (Hy C > 12 and Hy C < 12), and concentrations of persistent organic pollutants (polychlorinated biphenyls, polycyclic aromatic hydrocarbons [PAHs], p-p-Dichlorodiphenyldichloroethylene (4,4′-DDE), and Hexachlorobenzene (HCB). General relationships between studied variables and harbors systems were explored by multivariate statistical approaches. Results show that wide fluctuations are reported for all variables both among harbors and inside each studied system. Principal components analysis suggests that major significance in explaining total average variability is due to lead, copper, zinc, silts, sands, and PAHs. No significance has been observed when testing nonmetric multidimensional scaling distributions relating with the factor “region,” while performing analyses on factor “main human activity,” a higher significance is observed. These results suggest a strong relationship between the main human use of marine systems and observed pollution levels in sediments.

Mathematical modelling of sediment chemicophysical parameters in a coastal lagoon to estimate high density seagrass meadow (Ruppia cirrhosa) distribution

In spring 2003, the pH, redox potential (Eh), grain-size (G), Total Nitrogen (TN), Total Phosphorus (TP) and Total Organic Carbon (TOC) were measured in superficial sediment samples from 83 sampling stations equally and randomly distributed inside the Orbetello lagoon. Localisation of the seagrass meadows (Ruppia cirrhosa) and the estimation of biomasses were carried out at the same time. A Landsat 7 multiband image of the study area was used to improve the spatial localisation of the sediment sampling sites and seagrass meadow distribution (GRASS GIS). Spatial distribution maps of the sediment measured values (pH, Eh, G, TN, TP and TOC) and seagrass meadow distribution and density were built using a geo-statistics software (g-stat). A simple mathematical model, based on the measured physical and chemical parameters of the sediment (Eh, pH, TP, G), was constructed to estimate seagrass meadow density and distribution in the Orbetello lagoon. Results of the model were used to elaborate a georeferenced map which was superimposed on the map constructed with seagrass density obtained in the field in order to evaluate the predictive power of the model. We found good agreement between the distribution of meadows recorded in the field with the suitable areas predicted by the model. Therefore, the constructed model could be a valid instrument for planning and evaluating management activities carried out in this lagoon.

As(V)-reduction to As(III) by arsenic-resistant Bacillus spp. bacterial strains isolated from low-contaminated sediments of the Oliveri-Tindari Lagoon, Italy

Five arsenic-resistant bacterial strains designated MT1, MT2, MT3, V1 and V2 were isolated from sediments of the Oliveri-Tindari Lagoon (Italy), which comprises six small lakes whose sediments contain low arsenic concentrations. Phylogenetic analysis of the 16S rRNA gene sequences assigned them to the genus Bacillus. Bacillus sp. strain MT3 showed higher tolerance to As(III) and As(V), as indicated by minimum inhibitory concentrations of 14 and 135 mmol−1, respectively. Bacillus sp. strain V1 showed growth inhibition at 14 mmol−1 in the presence of As(III) and at 68 mmol−1 in the presence of As(V), whereas the arsenic resistance of Bacillus sp. strain MT1 was 10 and 27 mmol−1 for As(III) and As(V), respectively. The strains Bacillus spp. MT2 and V2 showed low levels of As(III) and As(V) resistance, as it was unable to grow at concentrations>7 and 14 mmol−1, respectively. The isolated arsenic-resistant Bacillus spp. strains were able to reduce As(V) to As(III), especially Bacillus spp. strain MT3. This study suggests that the isolated bacterial strains play a role in the arsenic biogeochemical cycle of arsenic-poor sediments in the Oliveri-Tindari Lagoon.

Contamination levels and state assessment in the lakes of the Oliveri-Tindari Lagoon (North-Eastern Sicily, Italy)

The Oliveri-Tindari Lagoon, located in North-Eastern Sicily (Italy) and composed of six lakes, is subject to continuous environmental changes. An integrated study focusing on sediment features and levels of contamination was carried out for three of the six lakes, which are of ancient origin: Verde, Mergolo della Tonnara and Marinello. A high primary production (26.89 μg l−1) was detected at Lake Verde; texture classification showed a typical grain size in the sediments of all lakes; the study of macronutrients highlighted 17.08 of total carbon in sediments from Lake Mergolo della Tonnara; toxic elements were detected at higher concentrations in the sediments of Lake Marinello in comparison to the others, while arsenic was found in high concentrations in all the samples tested, especially in Lake Verde, with a mean value of 17.25 mg kg−1 dry weight (d.w.). All the organic contaminants, except 4, 4′-dichlorodiphenyldichloroethylene, were below the detection limits in the sediments. Minimal microbiological contamination was found in both water and sediment samples. In the latter, we isolated several bacterial strains thriving in the presence of arsenic, which play a role in the biogeochemical cycle of arsenic. These preliminary results, obtained for the first time using a multidisciplinary approach, provide general information about the Oliveri-Tindari Lagoon area.