RESUMO
Coral reefs are among the most productive ecosystems on the planet, but are rapidly declining due to global-warming-mediated changes in the oceans. Particularly for the Caribbean region, Acropora sp. stony corals have lost â¼80% of their original coverage, resulting in vast extensions of dead coral rubble. We analyzed the microbial composition of biofilms that colonize and lithify dead Acropora palmata rubble in the Mexican Caribbean and identified the microbial assemblages that can persist under scenarios of global change, including high temperature and low pH. Lithifying biofilms have a mineral composition that includes aragonite and magnesium calcite (16 mole% MgCO(3)) and calcite, while the mineral phase corresponding to coral skeleton is basically aragonite. Microbial composition of the lithifying biofilms are different in comparison to surrounding biotopes, including a microbial mat, water column, sediments and live A. palmata microbiome. Significant shifts in biofilm composition were detected in samples incubated in mesocosms. The combined effect of low pH and increased temperature showed a strong effect after two-week incubations for biofilm composition. Findings suggest that lithifying biofilms could remain as a secondary structure on reef rubble possibly impacting the functional role of coral reefs.
Assuntos
Antozoários/microbiologia , Biofilmes/classificação , Microbiota/genética , Animais , Sequência de Bases , Carbonato de Cálcio/metabolismo , Região do Caribe , Recifes de Corais , DNA Bacteriano/genética , Ecossistema , Temperatura Alta , Concentração de Íons de Hidrogênio , Compostos de Magnésio/metabolismo , México , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
The chemotherapeutic agent cisplatin (cDDP) is widely used to treat a variety of solid and hematological tumors. However, cDDP exerts severe side effects, such as nephrotoxicity, neurotoxicity, and bone-marrow suppression. The use of some dietary compounds to protect organs that are not targets in association with chemotherapy has been encouraged. This study evaluated the protective effects of chlorophyll b (CLb) on DNA damage induced by cDDP by use of single-cell gel electrophoresis (SCGE) assays. Further, this investigation also determined platinum (Pt) and magnesium (Mg) bioaccumulation in mice tissues after treatment with CLb alone and/or in association of cDDP (simultaneous treatment) by inductively coupled plasma-mass spectroscopy (ICP-MS). All parameters were studied in peripheral blood cells (PBC), kidneys, and liver of mice after administration of CLb (0.2 or 0.5 mg/kg of body weight [b.w.]), cDDP (6 mg/kg b.w.), and the combination CLb 0.2 plus cDDP or CLb 0.5 plus cDDP. Pt accumulation in liver and kidneys was higher than that found in PBC, while DNA damage was higher in kidneys and liver than in PBC. Further, treatment with CLb alone did not induce DNA damage. Evidence indicates that genotoxic effects produced by cDDP may not be related to Pt accumulation and distribution. In combined treatments, CLb decreased DNA damage in tissues, but the PT contents did not change and these treatments also showed that CLb may be an important source of Mg. Thus, our results indicate that consumption of CLb-rich foods may diminish the adverse health effects induced by cDDP exposure.
Assuntos
Antimutagênicos/farmacologia , Antineoplásicos/toxicidade , Clorofila/farmacologia , Cisplatino/toxicidade , Dano ao DNA/efeitos dos fármacos , Animais , Antineoplásicos/farmacocinética , Cisplatino/farmacocinética , Ensaio Cometa , Feminino , Rim/efeitos dos fármacos , Rim/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Compostos de Magnésio/metabolismo , Masculino , Camundongos , Compostos de Platina/metabolismoRESUMO
We studied the precipitation of carbonates in 17 strains of moderately halophilic, Gram-positive cocci belonging to two species: Marinococcus halophilus and Marinococcus albus, isolated from the Salar de Atacama (Chile). They were cultivated in solid and liquid laboratory media for 42 days at salt concentrations (wt/vol) of 3%, 7.5%, 15%, and 20%. The bioliths precipitated were studied by X-ray diffraction and scanning electron microscopy. M. halophilus formed crystals at each of the salt concentrations, with a maximum number of strains capable of precipitating carbonates at 7.5% and 15% salt concentrations. M. albus did not precipitate at 20% and showed a maximum at 7.5%. This behavior is similar to that of other gram-positive bacteria and differs from that found in gram-negative bacteria. The bioliths precipitated were spherical, generally isolated, with a size of 10-100 microm, varying with salinity. They were of magnesium calcite (CO3 Ca1-x Mgx) with Mg content increasing with increasing salinity and Mg/Ca molar ratio of the culture medium. These results demonstrate the active role played by M. halophilus and M. albus in the precipitation of carbonates.