Zymomonas

Abstract

Zy.mo' mo.nas or Zy.mo.mo' nas . Gr. n. zyme leaven, ferment; Gr. n. monas a unit, monad; M.L. fem. n. Zymomonas fermenting monad. Proteobacteria / Alphaproteobacteria / Sphingomonadales / Sphingomonadaceae / Zymomonas Rod‐shaped cells with rounded ends , occasionally ellipsoidal, usually in pairs, 2–6 × 1.0–1.4 µm. Gram negative. Usually non‐motile ; if motile , they possess one to four polar flagella . Motility may be lost spontaneously. Facultatively anaerobic ; some strains are obligately anaerobic . Optimum temperature 25–30°C. Colonies on the standard medium 1 are glistening, regularly edged, white to cream colored, 1–2 mm in diameter after 2 d at 30°C. Oxidase negative. Chemoorganotrophic, growing on and fermenting 1 mol of glucose or fructose to almost 2 mol of ethanol , 2 mol of CO 2 , and some organic acids such as lactic acid . Some strains may also utilize sucrose, but other carbon sources are not used. Gluconate can be degraded but does not serve as sole carbon or energy source (Strohdeicher et al., 1 988). Sorbitol and gluconolactone are formed when grown on sucrose or mixtures of glucose and fructose by a so far unique enzyme, glucose‐fructose oxidoreductase. Membranes contain pentacyclic triterpenoids of the hopane series (Sahm et al., 1 993). Gelatinase negative. Nitrates are not reduced and indole is not produced. Zymomonas tolerates 5 % ethanol and is acid tolerant , growing at pH 3 . 5–7 . 5 . Good growth is obtained only when a mixture of amino acids is present in the medium, but no one amino acid is essential. All strains require biotin and pantothenate. Zymomonas occurs as a spoiler in beers , ciders , and perries ; as fermenting agents in Agave sap, palm sap, and sugarcane juice; and on honeybees and in ripening honey. The mol % G + C of the DNA is : 47.5–49.5. Type species : Zymomonas mobilis (Lindner 1 928a) Kluyver and van Niel 1 936, 399 ( Thermobacterium mobile Lindner 1 928b, 253; Zymomonas anaerobia Kluyver 1 957, 199.)