ABSTRACT
'Candidatus Magnetobacterium bavaricum' is unusual among magnetotactic bacteria (MTB) in terms of cell size (8-10 µm long, 1.5-2 µm in diameter), cell architecture, magnetotactic behaviour and its distinct phylogenetic position in the deep-branching Nitrospira phylum. In the present study, improved magnetic enrichment techniques permitted high-resolution scanning electron microscopy and energy dispersive X-ray analysis, which revealed the intracellular organization of the magnetosome chains. Sulfur globule accumulation in the cytoplasm point towards a sulfur-oxidizing metabolism of 'Candidatus M. bavaricum'. Detailed analysis of 'Candidatus M. bavaricum' microhabitats revealed more complex distribution patterns than previously reported, with cells predominantly found in low oxygen concentration. No correlation to other geochemical parameters could be observed. In addition, the analysis of a metagenomic fosmid library revealed a 34 kb genomic fragment, which contains 33 genes, among them the complete rRNA gene operon of 'Candidatus M. bavaricum' as well as a gene encoding a putative type IV RubisCO large subunit.
Subject(s)
Bacteria/classification , Metagenomics , Phylogeny , Amino Acid Sequence , Bacteria/genetics , Bacteria/ultrastructure , DNA, Bacterial/genetics , Ecology , Geologic Sediments/microbiology , Molecular Sequence Data , RNA, Ribosomal, 16S/genetics , Ribulose-Bisphosphate Carboxylase/genetics , Sequence Analysis, DNA , Water MicrobiologyABSTRACT
In the rat vas deferens, DMPP is a substrate of uptake1 (Km = 11.5 mumol/l). After block of vesicular uptake, monoamine oxidase and catechol-O-methyl transferase, after loading of the tissue with 3H-noradrenaline, and in calcium-free solution (i.e., when axoplasmic 3H-noradrenaline levels were high and when depolarization-induced exocytotic release was impossible), DMPP induced a pronounced outward transport of 3H-noradrenaline. On the other hand, when, in similar experiments, vesicular uptake and monoamine oxidase were intact (i.e., when axoplasmic 3H-noradrenaline levels were low), DMPP induced very little outward transport of 3H-noradrenaline. This discrepancy indicates that DMPP has little ability to mobilize vesicularly stored 3H-amine. When the medium contained calcium (catechol-O-methyl transferase inhibited, all other mechanisms intact), 100 (but not 10) mumol/l DMPP induced a hexamethonium-sensitive release of 3H-noradrenaline of short duration. Hence, in the presence of extracellular calcium, 100 mumol/l DMPP elicits exocytotic release via activation of hexamethonium-sensitive nicotinic acetylcholine receptors. DMPP inhibits the monoamine oxidase of rat heart homogenate with an IC50 of about 100 mumol/l.
