Spirillum

from WordNet (r) 3.0 (2006)

spirillum
    n 1: spirally twisted elongate rodlike bacteria usually living
         in stagnant water
    2: any flagellated aerobic bacteria having a spirally twisted
       rodlike form [syn: {spirillum}, {spirilla}]

from The Collaborative International Dictionary of English v.0.48

Spirillum \Spi*ril"lum\, n. [NL., dim. of L. spira a coil.]
   1. (Biol.) A genus of common gram-negative motile
      microorganisms (family {Spirillaceae}) having the form of
      spiral-shaped filaments. They are obligately
      microaerophilic, and do not ferment carbohydrates.
      --Stedman.
      [1913 Webster]

   2. A species of bacteria ({Borrelia recurrentis}, also known
      as {Obermeier's spirillum}), once believed to belong to
      the genus {Spirillum}, which causes relapsing fever.
      [PJC]