Genus/species (aliases): Gluconacetobacter oboediens (Acetobacter oboediens)
Type Strain: DSM 11826, LTH 2460
Gram Stain: Negative
Morphology:
Cell: rod-shaped bacteria
Colony:
Liquid Growth:
Physiological Traits:
Species of the Gluconacetobacter genus have the ability to use mannitol as a carbon source, which is one characterization for their classification. Species of the Gluconacetobacter genus, like Ga. oboediens, can be grown successfully on mannitol agar as it is their preferred carbon source. However, other carbon sources such as glucose, fructose and ethanol can be used by the bacteria. Another characteristic that has been used to classify Gluconacetobacter is the Q-10 ubiquinone isoprenologue present in its species Ga. oboediens is aerobic and therefore requires oxygen for growth (although some species of the Acetobacteraceae have been found growing in the semi-anaerobic environment at the bottom of wine barrels and other containers).The optimal temperature for Ga. oboediens to grow is between 25-30°C and the optimal pH growth is between 5.5-6.3.They are also ethanol tolerant. However, the bacteria can survive at wine pH of 3.0-4.0.Like all Acetobacteraceae, Ga. oboediens produces gluconic acid when glucose is used as the carbon source and oxofructose when fructose is used as the carbon source. In wines, when ethanol is the carbon source, acetic acid is produced. The conversion of ethanol to acetic acid by acetic acid bacteria (AAB), such as Ga. oboediens, produces acetaldehyde and ethyl acetate as by products. Ascorbic acid and cellulose are additional products of Ga. oboediens and other AAB.
Ecological Traits:
Ga. oboediens can be found in nature in sugary plants such as fruits and flowers. The bacteria can be found growing in grapes and in this way can be brought into a winery where they will continue to prosper due to their ethanol tolerance.In addition, they may be found in spoiled fruits that ferment naturally.
Distinguishing Features:
There are two characteristics that distinguish the genus Gluonacetobacter from the rest of the AAB—their affinity for mannitol and their Q-10 ubiquinone isoprenologue. In order to further separate Ga. oboediens from the rest of the Gluconacetobacter genus, PCR-RFLP, PCR or some other test on the chromosomal or DNA level needs to be used.
Role in wine:
Ga. oboediens can be present naturally in grapes, especially damaged ones, and from there brought into a winery. The species also flourishes in the winery in musts and wines. As an AAB, is considered a wine and must contaminant. The byproducts and end products of Ga. oboediens and other AAB, such as acetic acid, gluconic acid, oxofructose, and acetaldehyde, have negative sensory characteristics and can cause spoilage in the finished wine. Compounds like acetaldehyde, gluconic acid and oxofructose can bind with free SO2, resulting in the need for a higher addition of SO2 to get rid of the bacteria and other undesirable organisms in the must or wine. The presence of the bacteria can cause sluggish or stuck fermentations, especially if the lag phase of the yeast is slow, allowing the bacteria to flourish and use up much of the nutrients. Even at low levels, Ga. oboediens and other AAB can have a significant impact on the wine due to their ability to produce a high quantity of acetic acid.
Sensitivities:
- SO2: sensitive
- Sorbate: tolerant
- DMDC: unknown
- pH: sensitive to high and low pH
- Acids: sensitive to some acids
- Ethanol: tolerant
- Anaerobiosis: sensitive (with some exceptions)
- Heat: sensitive to high temps