Mónica D. Baldini

Effects of Bacillus subtilis O9 biosurfactant on the bioremediation of crude oil-polluted soils

The application of a surfactant from Bacillus subtilis O9 (Bs) on the bioremediation of soils polluted with crude oil was assayed in soil microcosms under laboratory conditions. Three concentrations of biosurfactant were assayed (1.9, 19.5, and 39 mg kg−1 soil). Microcosms without biosurfactant were prepared as controls. During the experiment, the crude oil-degrading bacterial population, the aliphatic and aromatic hydrocarbons were monitored in each microcosm. The results indicated that applying Bs did not negatively affect the hydrocarbon-degrading microbial population Concentrations of 19 and 19.5 mg (Bs) per kilogram of soil stimulated the growth of the population involved in the crude oil degradation, and accelerated the biodegradation of the aliphatic hydrocarbons. However, none of the assayed Bs concentrations stimulated aromatic hydrocarbon degradation.

Evaluation of faecal contamination in Bahía Blanca estuary (Argentina) using a numerical model

Es conocida la necesidad de contar con tecnicas y sitios adecuados para la eliminacion de efluentes cloacales. El lugar mas utilizado para la descarga de los mismos, tratados o no, es un cuerpo de agua cercano. En Bahia Blanca en septiembre de 2008 comenzo a operar una planta de tratamiento de efluentes cloacales que vuelca los liquidos insuficientemente tratados en el area cercana a una pileta Municipal (Balneario Maldonado). Debido a la proximidad, una parte importante de las aguas residuales podria alcanzar dicha pileta con el correspondiente riesgo sanitario. La finalidad de este estudio fue evaluar la salud de las aguas de la parte interna del estuario de Bahia Blanca, aplicando un modelo numerico (MOHID), utilizando como indicador de contaminacion fecal la bacteria Escherichia coli. Se valido el modelo de dispersion de contaminacion fecal, de modo de poder utilizarlo como una herramienta integral de gestion. El MOHID utilizo el concepto de trazadores lagrangianos para evaluar la evolucion espacio-temporal de la pluma de contaminacion, determinada por el regimen de mareas, vientos y la circulacion local. El modelo predijo con precision la variabilidad y los recuentos medios de los microorganismos indicadores en la mayoria de los sitios muestreados (r > 0,9) y muestran el impacto ambiental sobre la pileta Municipal. Se espera que las simulaciones del modelo MOHID descritas en este documento sean una herramienta util y de esta manera generar un esfuerzo por parte de las autoridades competentes para reducir la contaminacion en el estuario de Bahia Blanca.

Microbial enumeration of different functional groups and bacterial behavior in acid basic conditions of a biotoxic landfill leachate of Bahía Blanca, Argentina.

Leachate is liquid waste from refuse biological decomposition or rainwater percolation in a landfill. This research focused on leachate produced by a landfill in Bahia Blanca, Buenos Aires, Argentina. The research studied the main microbial populations involved in wastewater treatment, analyzed the behavior of bacteria isolated from leachate at different pH values, and appraised leachate biotoxicity. The number of bacteria varied by type, ranging from 1 x 10(4) to 1 x 10(5) CUF/mL aerobic heterotrophic bacteria (AHB); 1 x 10(3) to 1 x 10(5) CUF/mL anaerobic heterotrophic bacteria (ANHB); 1 x 10(5) to 1 x 10(6) CUF/mL sulfite-reducing bacteria (SRB); 1 x 10(3) to 1 x 10(6) NMP/mL nitrate-reducing bacteria (NRB); and 1 x 10(2) to 1 x 10(4) NMP/mL ammonium-oxidizing bacteria (AOB). Several microbial strains developed at pH 5, 7, and 10. These pH values changed to 9 in the culture media after a 48-hour incubation. Leachate was used to water lettuce seeds (Lactuca sativa capitata). Its toxicity was proved by full inhibition of plant development.

Electroactive Mg2+-Hydroxyapatite Nanostructured Networks against Drug-Resistant Bone Infection Strains

Surface colonization competition between bacteria and host cells is one of the critical factors involved in tissue/implant integration. Current biomaterials are evaluated for their ability both of withstanding favorable responses of host tissue cells and of resisting bacterial contamination. In this work, the antibacterial ability of biocompatible Mg2+-substituted nanostructured hydroxyapatite (HA) was investigated. The densities of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli strains were significantly decreased after culture in the presence of Mg-substituted HA materials in direct correlation with Mg2+-Ca2+ switch in the HA lattice. It was noticed that this decrease was accompanied by a minimal alteration of bacterial environments; therefore, the Mg2+-HA antibacterial effect was associated with the material surface topography and it electroactive behavior. It was observed that 2.23 wt % Mg2+-HA samples exhibited the best antibacterial performance; it decreased 2-fold the initial population of E. coli, P. aeruginosa, and S. aureus at the intermediate concentration (50 mg mL-1 of broth). Our results reinforce the potential of Mg-HA nanostructured materials to be used in antibacterial coatings for implantable devices and/or medicinal materials to prevent bone infection and to promote wound healing.

Biogeochemical and hydrological drivers of the dynamics of Vibrio species in two Patagonian estuaries.

The ecology of the most relevant Vibrio species for human health and their relation to water quality and biogeochemistry were studied in two estuaries in Argentinian Patagonia. Vibrio cholerae and Vibrio parahaemolyticus were reported in >29% of cases at the Río Colorado and Río Negro estuaries. Neither the pandemic serogroups of Vibrio cholerae O1, Vibrio cholerae O139 nor the cholera toxin gene were detected in this study. However, several strains of V. cholerae (not O1 or O139) are able to cause human disease or acquire pathogenic genes by horizontal transfer. Vibrio vulnificus was detected only in three instances in the microplankton fraction of the Río Negro estuary. The higher salinity in the Río Colorado estuary and in marine stations at both estuaries favours an abundance of culturable Vibrio. The extreme peaks for ammonium, heterotrophic bacteria and faecal coliforms in the Río Negro estuary supported a marked impact on sewage discharge. Generally, the more pathogenic strains of Vibrio have a faecal origin. Salinity, pH, ammonium, chlorophyll a, silicate and carbon/nitrogen ratio of suspended organic particulates were the primary factors explaining the distribution of culturable bacteria after distance-based linear models. Several effects of dissolved organic carbon on bacterial distribution are inferred. Global change is expected to increase the trophic state and the salinisation of Patagonian estuaries. Consequently, the distribution and abundance of Vibrio species is projected to increase under future changing baselines. Adaptation strategies should contribute to sustaining good water quality to buffer climate- and anthropogenic- driven impacts.

Multi-drug delivery system based on lipid membrane mimetic coated nano-hydroxyapatite formulations

ABSTRACT Local delivery systems from an osteoconductive biomaterial are suggested as a promising strategy to avoid simultaneously peri‐implant traumas and to induce tissue regeneration. In this work, it is detailed the design and construction of a multi‐drug delivery formulation based on lipid membrane mimetic coated nano‐hydroxyapatite, LMm/nano‐HA, as a bone‐specific drug delivery approach. The optimal LMm/nano‐HA formulation was selected after analysing the lipid/nano‐HA interaction by dynamic light scattering (DLS), &zgr;‐potential, transmission electron microscopy (TEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC) and UV–vis spectroscopy. After the initial screening, Ciprofloxacin and Ibuprofen simultaneous ‐load and ‐release efficiency from selected LMm/nano‐HA was assessed. pH‐responsive kinetic profiles of local drug distribution were characterized and compared with currently applied systemic doses. Finally, the systems’ biocompatibility and drug released activity were positively validated. The obtained results demonstrated that LMm/nano‐HA formulations can represent a valuable multi‐modal platform in bone tissue therapies.

Aporte de los afluentes a la contaminación fecal del estuario de Bahía Blanca, Argentina

Bahia Blanca estuary, Argentina, receives the contribution of the Naposta Grande stream and the Sauce Chico river. Channel Maldonado and the Saladillo de Garcia stream are minor tributaries whose contribution is meaningful only during periods of high rainfall. The objective of the study was to determine the health status of the main tributaries that the estuary of Bahia Blanca receives, quantifying populations of heterotrophic mesophilic aerobic bacteria (BH), Escherichia coli (EC) and Salmonella spp., as well as to set the impact they have on the estuary. Significant differences between the stations for both EC (p < 0.02) and BH (p < 0.01) were found. The comparison of means (LDS Fisher) showed that the significant differences detected by ANOVA for both indicators corresponded to the Maldonado Channel. In the other three stations, we could not say pollution differed significantly (p < 0.05). Salmonella spp. was detected in 50 % (11/22) of the samples of the Maldonado Channel and in 45 % (10/22) of the Naposta stream. Maldonado Channel and Naposta stream are the courses with greatest impact on the estuary. Garcia de Saladillo stream and the Sauce Chico river, showed a similar behavior and are not a problem of contamination of the estuary. The Bahia Blanca estuary is heavily impacted by human activity, which maintains high concentrations of faecal bacteria in certain areas. This problem will remain if the clandestine dumps sewage arriving through fresh water courses are not controlled.