RESUMO
BACKGROUND: Magnetotactic bacteria (MTB) are a unique group of prokaryotes that have a potentially high impact on global geochemical cycling of significant primary elements because of their metabolic plasticity and the ability to biomineralize iron-rich magnetic particles called magnetosomes. Understanding the genetic composition of the few cultivated MTB along with the unique morphological features of this group of bacteria may provide an important framework for discerning their potential biogeochemical roles in natural environments. RESULTS: Genomic and ultrastructural analyses were combined to characterize the cultivated magnetotactic coccus Magnetofaba australis strain IT-1. Cells of this species synthesize a single chain of elongated, cuboctahedral magnetite (Fe3O4) magnetosomes that cause them to align along magnetic field lines while they swim being propelled by two bundles of flagella at velocities up to 300 µm s-1. High-speed microscopy imaging showed the cells move in a straight line rather than in the helical trajectory described for other magnetotactic cocci. Specific genes within the genome of Mf. australis strain IT-1 suggest the strain is capable of nitrogen fixation, sulfur reduction and oxidation, synthesis of intracellular polyphosphate granules and transporting iron with low and high affinity. Mf. australis strain IT-1 and Magnetococcus marinus strain MC-1 are closely related phylogenetically although similarity values between their homologous proteins are not very high. CONCLUSION: Mf. australis strain IT-1 inhabits a constantly changing environment and its complete genome sequence reveals a great metabolic plasticity to deal with these changes. Aside from its chemoautotrophic and chemoheterotrophic metabolism, genomic data indicate the cells are capable of nitrogen fixation, possess high and low affinity iron transporters, and might be capable of reducing and oxidizing a number of sulfur compounds. The relatively large number of genes encoding transporters as well as chemotaxis receptors in the genome of Mf. australis strain IT-1 combined with its rapid swimming velocities, indicate that cells respond rapidly to environmental changes.
Assuntos
Adaptação Fisiológica/genética , Alphaproteobacteria/genética , Alphaproteobacteria/fisiologia , Meio Ambiente , Genômica , Alphaproteobacteria/citologia , Alphaproteobacteria/metabolismo , Magnetossomos/metabolismo , Minerais/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transcrição GênicaRESUMO
An extremely polymorphous intraerythrocytic microorganism occurring in naturally infected turkeys, ducks and fowls has been discovered in the states of Minas Gerais, Rio de Janeiro and Espirito Santo. 2. Studies on the morphology and biology have shown that it is a hitherto undescribed heteroxenous parasite for which the name Neitziella rezendei gen. nov., sp. nov. is proposed. 3. Its morphological features permit its inclusion in the class Microtatobiotes and order Rickettsiales. 4. Microscopical examination of blood films have shown that the parasitic carrier state in turkeys persists for more than 200 days (endpoint not determined). 5. The natural mode of transmission needs to be determined. 6. The suspicion that the parasite may cause illthrift and deaths in poultry requires confirmation.