RESUMO
Stable associations of more than one species of symbiont within a single host cell or tissue are assumed to be rare in metazoans because competition for space and resources between symbionts can be detrimental to the host. In animals with multiple endosymbionts, such as mussels from deep-sea hydrothermal vents and reef-building corals, the costs of competition between the symbionts are outweighed by the ecological and physiological flexibility gained by the hosts. A further option for the coexistence of multiple symbionts within a host is if these benefit directly from one another, but such symbioses have not been previously described. Here we show that in the gutless marine oligochaete Olavius algarvensis, endosymbiotic sulphate-reducing bacteria produce sulphide that can serve as an energy source for sulphide-oxidizing symbionts of the host. Thus, these symbionts do not compete for resources but rather share a mutalistic relationship with each other in an endosymbiotic sulphur cycle, in addition to their symbiotic relationship with the oligochaete host.
Assuntos
Deltaproteobacteria/metabolismo , Gammaproteobacteria/metabolismo , Oligoquetos/microbiologia , Sulfatos/metabolismo , Sulfetos/metabolismo , Simbiose , Aerobiose , Ágar , Animais , Dióxido de Carbono/metabolismo , Deltaproteobacteria/genética , Deltaproteobacteria/ultraestrutura , Gammaproteobacteria/genética , Gammaproteobacteria/ultraestrutura , Hibridização in Situ Fluorescente , Cinética , Funções Verossimilhança , Microscopia Eletrônica , Modelos Biológicos , Dados de Sequência Molecular , Oligoquetos/ultraestrutura , Oxirredução , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Dióxido de Silício , Enxofre/metabolismoRESUMO
The influence of the composition and the casting process upon the electrochemical corrosion of a selection of palladium-based alloys and non-precious metal alloys has been investigated in vitro using an electrochemical method. No influence of the casting process upon the corrosion resistance was observed with palladium-based alloys. Changes in the crystallographic structure effected by the different composition of the alloys were found, the casting process did not cause significant effects. With nickel-chromium alloys rather low corrosion stabilities were observed.
