Genus/species: Acetobacter orleanensis
Gram Stain: Negative
Morphology:
- Cell: rod-shaped cells
- Colony: Acetobacter orleanensis is identified by its formation of clear zones on plates with agar containing CaCO3.
- Liquid Growth: This organism has dispersed liquid growth
Physiological Traits:
Acetobacter orleanensis oxidizes ethanol into acetic acid. It will also oxidize glucose into gluconic acid. Acetobacter orleanensis will produce 2-ketogluconate but not 5-ketogluconate. It will not produce acid from d-arabinose, d-fructose, isorbase, d-mannitol, d-sorbitol, glycerol, sucrose, or lactose. This bacteria is capable of utilizing organic acids as substrates, but they are not the preferred substrates for this organism. This organism has a high requirement of oxygen present in its environment. The lysis of yeast cells provides Acetobacter with necessary amino acids and vitamins. The nutrients added by dying yeast cells combined with the aeration of a wine, by such processes as pumpovers or bottling, can stimulate growth of Acetobacter orleanensis.
Ecological Traits:
Acetobacter orleanensis is naturally found in high sugar environments such as fruits or flowers. Due to its high ethanol tolerance, it does well in environments containing alcohol such as spoiled fruits or fermenting juices. This microbe can also be found on winery equipment.
Distinguishing Features:
Acetobacter orleanensis oxidizes alcohol into acetic acid. Its presence in wine is often indicated by increased presence of acetic acid and thus a high volatile acidity. This organism can also be identified by its rod shaped cells, and the clear zones it forms on plates with CaCO3. Acetobacter orleanensis is also catalase positive.
Role in wine:
Acetobacter orleanensis is considered a spoilage organism in wine as can result in a wine with an unacceptably high volatile acidity as well as grow in bottled wines.
Sensitivities:
- SO2: Is sensitive to SO2
- Sorbate:
- DMDC: sensitive to DMDC
- pH:
- Acids:
- Ethanol:
- Anaerobiosis: Requires significant amount of oxygen to grow, CO2 is inhibitory as it drives off the oxygen in the cells’ envirnment.
- Heat: Optimal temperature is 25-30 degrees C, higher and lower temperatures are inhibitory. Bacteria are particularly sensitive to lower temperatures, though some are adapted to cool temperatures and will continue to grow.
References:
- Guillamon, J.M., and Mas, A., 2009 Biology of Microorganisms on Grapes, In Must and in Wine: Acetic Acid Bacteria. Springer-Verlag Berlin Heidelberg, pg:44-58
- Sievers, M., and Swings, J., Bergey’s Manual of Systemic Bacteriology. 2005 Springer US pg: 51-54
- Boulton, R.B., Singleton,. V., Bisson, L., and Kunkee, R., Principles and Practices of Winemaking. 1996 Chapman Hall, New York