Spirillum is microbiologically characterized as a gram-negative, motile helical cell with tufts of whiplike flagella at each end. The helix of the largest spirillum, S. volutans, is 5 to 8 μm (micrometres; 1 μm = 10-6 metre) across by 60 μm long.
Spirilla possess a strictly respiratory metabolism, with oxygen as the terminal electron acceptor; they are oxidase- and catalase-positive, an usually phosphate-positive. Large clusters of flagella are present on each end of the cell to help with movement.
The difference between spirillum and spirochaete is that the former possesses a rigid, non-flexuous cell body, while the latter has a flexuous cell body and no true flagella.
Members of the genus Spirillum were probably first described in the 1670s by van Leeuwenhoek and a century later by Muller. The genus Spirillum was created in 1832 by Ehrenberg, and from his descriptions of members of the genus in 1838 it is clear that rigid helical cells were being described rather than flexible cells such as spirochetes.
Spiral bacterium – Spirillum spp.
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| Spirillum volutans |
