Acetic acid bacteria

The family Acetobacteraceae consists of gram-negative aerobic bacteria known in agronomy primarily as agents of biological spoilage rather than primary plant pathogens. These bacteria specialize in the oxidation of ethanol into acetic acid, a process that significantly alters the chemical composition and sensory qualities of fruit and vegetable tissues.

The economic impact of Acetobacteraceae is most evident in the post-harvest period and during the ripening phase in orchards and vineyards. Infestation leads to tissue softening, acidification, and the release of strong acetic odors. This renders fruits unsuitable for fresh market consumption and processing, as the fermentation process destroys the integrity of the plant cell walls.

Fruit-bearing crops with high sugar content, such as grapes, apples, pears, and various berries, are the most susceptible. The infection is almost always opportunistic, occurring at sites of physical trauma—such as cracks caused by rain, insect punctures, or hail damage. Once the sugar-rich juice is exposed, these bacteria colonize the surface, often creating a visible biofilm or slime.

Environmental conditions that favor the proliferation of these bacteria include warm temperatures and high humidity, which facilitate the metabolic activity of the Acetobacteraceae family. Insects, particularly fruit flies (Drosophila spp.), act as primary vectors, facilitating the spread of bacteria throughout the canopy. In storage facilities, poor ventilation can accelerate the contamination process, turning a minor infection into widespread rot.

Effective management and protection require a focus on physical integrity and environmental control:

• Integrated pest management (IPM) to reduce insect damage that allows bacterial entry.
• Sanitary practices, including the removal of rotting fruit and debris from the orchard floor.
• Ensuring careful handling during harvest to minimize mechanical bruises and skin ruptures.
• Optimizing storage environments by maintaining cool temperatures and adequate air circulation.
• Timely application of protective measures to prevent primary fruit diseases that create entry points for opportunistic bacteria.