TABLE 1.

Ultrastructural analysis of magnetosomes in magnetosome mutants: particle shapes^a and chain-types

^aDark-colored hexagons: regularly shaped and sized, WT-like magnetosomes; dark-colored spiny shapes: irregular magnetosomes; smaller light-colored shapes: thin irregularly shaped, sometimes needle-like particles (flakes) or other aberrantly shaped structures. Selected Wmag clones with Tn5 insertions outside MAI (exMAI) in genes of different functional categories (electron transport, cytochrome c maturation, structural disulfide bond formation, amino acid transport) were analyzed by TEM analysis. Here, we summarize the range of typical aberrations with respect to magnetic crystal size and/or number that we found in cells with a Wmag phenotype compared to the that for the wild type. In most cases, cells show shorter magnetosome chains with wild-type crystal morphologies interspersed by more or less defect crystal shapes and/or scattered flakes (80). Also, nearly regular chains with two distinct crystal types were observed. Magnetosome chains in the mutant cells typically retained their centered location but occasionally were also found delocalized at one of the poles. Apart from deviations in magnetosome structure and positioning, we observed general morphological peculiarities, such as aberrant cell shapes and sizes, or larger polyphosphate granules among Tn5 insertion mutants, but these are not described or quantified here.