Acetic acid bacteria
Encyclopedia
Acetic acid bacteria are bacteria that derive their energy from the oxidation of ethanol
to acetic acid
during fermentation
. They are Gram-negative
, aerobic
, rod-shaped bacteria. Not to be confused with the genus Acetobacterium
which are anaerobic homoacetogenic facultative autotrophs and can reduce carbon dioxide
to produce acetic acid. For example: Acetobacterium woodii
.
The acetic acid bacteria are usually airborne and are ubiquitous in nature. They are actively present in environment where ethanol is being formed as a result of fermentation of sugars. They can be isolated from the nectar
of flowers and from damaged fruit. Other good sources are fresh apple cider
and unpasteurized beer which has not been filter sterilized. In these liquids, they grow as a surface film due to their aerobic nature and active motility. Vinegar
is produced when acetic acid bacteria act on alcoholic beverages such as wine. Fruit flies
or Vinegar eels
are considered as a common vector in propagating acetic acid bacteria in nature.
Some genera, such as Acetobacter
, can eventually oxidize acetic acid to carbon dioxide
and water using Krebs cycle enzymes. Other genera, such as Gluconobacter, do not further oxidize acetic acid, as they do not have a full set of Krebs cycle enzymes.
Some acetic acid bacteria, notably Acetobacter xylinum, are known to synthesize cellulose
, something normally only done by plants.
As these bacteria produce acid, they are usually acid tolerant, growing well below pH 5.0, although the pH optimum for growth is 5.4-6.3.
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
to acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
during fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...
. They are Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, aerobic
Obligate aerobe
An obligate aerobe is an aerobic organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to oxidize substances, like sugars or fats, in order to obtain energy. During respiration, they use oxygen as the terminal electron acceptor...
, rod-shaped bacteria. Not to be confused with the genus Acetobacterium
Acetobacterium
Acetobacterium is a genus of gram-positive bacteria which belong to the Eubacteriaceae family. Usually they are homoacetogens, which means they predominantly produce acetic acid as a metabolic by-product. Not to be confused with acetic acid bacteria which are aerobic, gram-negative...
which are anaerobic homoacetogenic facultative autotrophs and can reduce carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
to produce acetic acid. For example: Acetobacterium woodii
Acetobacterium
Acetobacterium is a genus of gram-positive bacteria which belong to the Eubacteriaceae family. Usually they are homoacetogens, which means they predominantly produce acetic acid as a metabolic by-product. Not to be confused with acetic acid bacteria which are aerobic, gram-negative...
.
The acetic acid bacteria are usually airborne and are ubiquitous in nature. They are actively present in environment where ethanol is being formed as a result of fermentation of sugars. They can be isolated from the nectar
Nectar (plant)
Nectar is a sugar-rich liquid produced by plants. It is produced in glands called nectaries, either within the flowers, in which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide anti-herbivore protection...
of flowers and from damaged fruit. Other good sources are fresh apple cider
Cider
Cider or cyder is a fermented alcoholic beverage made from apple juice. Cider varies in alcohol content from 2% abv to 8.5% abv or more in traditional English ciders. In some regions, such as Germany and America, cider may be termed "apple wine"...
and unpasteurized beer which has not been filter sterilized. In these liquids, they grow as a surface film due to their aerobic nature and active motility. Vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...
is produced when acetic acid bacteria act on alcoholic beverages such as wine. Fruit flies
Drosophilidae
Drosophilidae is a diverse, cosmopolitan family of flies, which includes fruit flies. Another family of flies called Tephritidae also includes fruit flies. The best known species of Drosophilidae is Drosophila melanogaster, within the genus Drosophila, and this species Is used extensively for...
or Vinegar eels
Turbatrix aceti
Turbatrix aceti are free-living nematodes that feed on the microbial culture, called mother of vinegar used to create vinegar, and may be found in unfiltered vinegar...
are considered as a common vector in propagating acetic acid bacteria in nature.
Some genera, such as Acetobacter
Acetobacter
Acetobacter is a genus of acetic acid bacteria characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. There are several species within this genus, and there are other bacteria capable of forming acetic acid under various conditions; but all of the Acetobacter are...
, can eventually oxidize acetic acid to carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and water using Krebs cycle enzymes. Other genera, such as Gluconobacter, do not further oxidize acetic acid, as they do not have a full set of Krebs cycle enzymes.
Some acetic acid bacteria, notably Acetobacter xylinum, are known to synthesize cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
, something normally only done by plants.
As these bacteria produce acid, they are usually acid tolerant, growing well below pH 5.0, although the pH optimum for growth is 5.4-6.3.
Academic references
- Ecological occurrence of Gluconacetobacter diazotrophicus and nitrogen-fixing Acetobacteraceae members: their possible role in plant growth promotion 2008. Microb Ecol. 55(1):130-40.
- Genera and species in acetic acid bacteria, 2008 Int. J. Food Microbiol. Volume 125, Issue 1, Pages 15–24.
- Polyphasic taxonomy of acetic acid bacteria: An overview of the currently applied methodology, 2008 Int. J. Food Microbiol. Volume 125, Issue 1, Pages 2–14
- Biotechnological applications of acetic acid bacteria, 2008, Critical Reviews in Biotechnology, Volume 28, Issue 2, 101-124