Summary Magnetotactic bacteria ( MTB ), which orient along the earth's magnetic field using magnetosomes, are ubiquitous and abundant in marine and freshwater environments. Previous phylogenetic analysis of diverse MTB has been limited to few cultured species and the most abundant and conspicuous members of natural populations, which were assigned to various lineages of the P roteobacteria , the N itrospirae phylum as well as...

Summary Magnetotactic bacteria (MTB) are a diverse group of prokaryotes that orient along magnetic fields using membrane‐coated magnetic nanocrystals of magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ), the magnetosomes. Previous phylogenetic analysis of MTB has been limited to few cultivated species and most abundant members of natural populations, which were assigned to Proteobacteria and the Nitrospirae phyla. Here, we describ...

Summary Multicellular magnetotactic prokaryotes (MMPs) represent highly organized, spherical and motile aggregates of 10–40 bacterial cells containing magnetosomes. Although consisting of different cells, each with its own magnetosomes and flagellation, MMPs orient themselves within a magnetic field and exhibit magnetotaxis. So far, MMPs have only been found in several North and South American coastal lagoons and salt marshes....

Summary Marine Crenarchaeota represent an abundant component of the oceanic microbiota that play an important role in the global nitrogen cycle. Here we report the association of the colonial ascidian Cystodytes dellechiajei with putative ammonia‐oxidizing Crenarchaeota that could actively be involved in nitrification inside the animal tissue. As shown by 16S rRNA gene analysis, the ascidian‐associated Crenarchaeota were phylo...

Summary The ability to adhere onto surfaces is of very high importance for microorganisms, enabling them to stay in a favourable habitat for life. In the case of Bacteria cell surface organelles called fimbriae/pili have been shown to be used for adhesion; corresponding cell surface appendages of Archaea have not yet been defined. The first detailed characterization of archaeal fimbriae, namely those of Methanothermobacter the...

Summary Lower Kane Cave, Wyoming (USA), has hydrogen sulfide‐bearing springs that discharge into the cave passage. The springs and cave stream harbour white filamentous microbial mats dominated by Epsilonproteobacteria . Recently, novel 16S rRNA gene sequences from the phylum Acidobacteria , subgroup 7, were found in these cave mats. Although Acidobacteria are ubiquitously distributed in many terrestrial and marine habitats, l...

Summary The ascidian Cystodytes dellechiajei (Della Valle, 1877) (phylum Chordata, class Ascidiacea, family Polycitoridae) is a colonial tunicate that inhabits benthic rock environments in the Atlantic, Pacific and Indian Oceans, as well as the Mediterranean Sea. Its life cycle has two phases, the adult sessile colony and the free‐living larva. Both adult zooids and larvae are surrounded by a protective tunic that contains sev...