RESUMEN
Free living amoebae (FLA) can be found in different environments, where they feed on diverse microorganisms. Some bacteria preyed by FLA are called amoeba-resistant bacteria (ARB), as they can resist to lysosomal fusion and are capable of multiplying and evading FLA after internalization, propagating in the environment. Despite the health risks due to the existence of pathogenic and opportunistic species that are ARB and the pathogenicity of some FLA species, there are no water quality protocols to analyze the presence of ARB or FLA. In this sense, our study aimed to isolate FLA through amoebal enrichment and to identify ARB using amoebal coculture in water samples from a public park and two hospitals in southern Brazil. As a result, 9 different microorganisms genera have been identified through amoebal coculture, including fastidious Legionella spp. and Bosea vestrisii. From the positive samples for FLA, by amoebal enrichment, Acanthamoeba spp., Vermamoeba vermiformis and Naegleria spp. were identified in 14 amoebic isolates. The methodologies used in this work proved to be effective as simple and low-cost methods to be used in the implementation in water quality control of anthropogenic environments.
Asunto(s)
Amoeba , Monitoreo del Ambiente , Purificación del Agua , Amoeba/aislamiento & purificación , Bradyrhizobiaceae , Brasil , Técnicas de Cocultivo , Legionella , Control de Calidad , AguaRESUMEN
Tropical aquatic legumes of the genus Aeschynomene are unique in that they can be stem-nodulated by photosynthetic bradyrhizobia. Moreover, a recent study demonstrated that two Aeschynomene indica symbionts lack canonical nod genes, thereby raising questions about the distribution of such atypical symbioses among rhizobial-legume interactions. Population structure and genomic diversity were compared among stem-nodulating bradyrhizobia isolated from various Aeschynomene species of Central America and Tropical Africa. Phylogenetic analyses based on the recA gene and whole-genome amplified fragment length polymorphism (AFLP) fingerprints on 110 bacterial strains highlighted that all the photosynthetic strains form a separate cluster among bradyrhizobia, with no obvious structuring according to their geographical or plant origins. Nod-independent symbiosis was present in all sampling areas and seemed to be linked to Aeschynomene host species. However, it was not strictly dependent on photosynthetic ability, as exemplified by a newly identified cluster of strains that lacked canonical nod genes and efficiently stem-nodulated A. indica, but were not photosynthetic. Interestingly, the phenotypic properties of this new cluster of bacteria were reflected by their phylogenetical position, as being intermediate in distance between classical root-nodulatingBradyrhizobium spp. and photosynthetic ones. This result opens new prospects about stem-nodulating bradyrhizobial evolution.
Asunto(s)
Bradyrhizobiaceae/clasificación , Fabaceae/microbiología , Filogenia , Tallos de la Planta/microbiología , Simbiosis , África , Análisis del Polimorfismo de Longitud de Fragmentos Amplificados , Evolución Biológica , Bradyrhizobiaceae/genética , Bradyrhizobiaceae/fisiología , América Central , ADN Bacteriano/genética , Genoma Bacteriano , Datos de Secuencia Molecular , Fenotipo , FotosíntesisRESUMEN
Nitrifying bacteria were found to be widely distributed among the products of the weathering crust of ultrabasite rocks. Nitrosospira briensis and Nitrobacter winogradskyi involved in the first and second phases of nitrification, respectively, were detected and isolated as pure cultures. In experiments conducted with a pure culture of Nitrosospira briensis, a correlation was established between degradation of serpentinite by this culture and an increase in the content of nitrites in the growth medium. The presence of nitrogen compounds in the deposits, as well as wide distribution of nitrifying bacteria, suggests that this bacterial group along with other, in particular, heterotrophic microorganisms participates in weathering of serpentinized ultrabasite rocks, leaching of elements, and formation of the weathering crust.