Acetobacteria

The acetobacteria or acetic acid bacteria comprise a group of Gram-negative, motile bacilli that exhibit an aerobic metabolism capable of homoacetic fermentation, which relies on the ability to convert lactate to acetate, important in the anaerobic methanogenic process when lactate is a major intermediate metabolite, allowing other organisms such as methanogenic archaea in non-marine ecosystems to produce methane, a much more effective greenhouse gas than CO2 which is produced not only by anaerobic bacteria but plants as well. These bacteria carry out an incomplete oxidation of alcohols, producing an accumulation of organic acids as final products by oxidizing hydrogen and reducing carbon dioxide to acetic acid using the Wood Ljungdahl pathway, which allows the use of CO2 as an electron acceptor during their heterotrophic growth as autotrophic. When the substrate is ethanol, acetic acid is produced, a compound that can act as a microbicide in most bacteria since it can penetrate through cell membranes, causing cytoplasmic acidification by altering the proton gradient in susceptible cells, hence it derives the common name by which these bacteria are known. One property of this type of microorganisms is their high tolerance to acidity, due to the fact that they have an ethyl transporter driven by the proton gradient that behaves as an electroneutral proton symport transporter for the anionic form of the acid, allowing most Most strains can grow at pH less than 5. This acid tolerance is essential for an organism to produce large amounts of acid. Acetic acid bacteria are a heterogeneous group, comprising organisms with peritric or polar flagellation.

Organisms with polar flagellation are related to Pseudomonas, from which they differ mainly by their tolerance to acid and by their inability to fully oxidize alcohols. These organisms are currently included in the genus Gluconobacter. The genus Acetobacter includes organisms with peritrichous flagellation. In addition, Acetobacter is capable of oxidizing the acetic acid it produces to carbon dioxide, contrary to Gluconobacter.

In the industrial production of vinegar, cultures of acetic acid bacteria are used. The acetate produced by these and homoacetogens is also used (in the form of calcium salt) to melt ice on roads in winter.