ACETOBACTER: CHARACTERISTICS, HABITAT AND MAIN SPECIES - BIOLOGY - 2024

Acetobacter is a genus of gram-negative bacteria that encompasses a large number of species, many of them commercially important. It was first described in 1898 by the Dutch microbiologist Martinus Beijerinck.

The bacteria that make it up are pleomorphic, and can be rod-shaped or ovoid. They are also characterized by the ability to produce acetic acid from ethanol. This is a skill that has been exploited by man on a commercial level, in the production of vinegar and a wide variety of products derived from it.

Bacteria of the genus Acetobacter are used in the production of vinegar. Source: Pixabay

Taxonomy

The taxonomic classification of the genus Acetobacter is as follows:

• Domain: Bacteria
• Kingdom: Monera
• Phylum: Proteobacteria
• Class: Alphaproteobacteria
• Order: Rhodospirillales
• Family: Acetobacteraceae
• Genus: Acetobacter

characteristics

Most of the bacteria that make up the genus Acetobacter are Gram negative. This means that when they are subjected to gram staining they acquire a fuchsia coloration. This is because their cell wall does not have a thick enough peptidoglycan layer to retain the dye particles.

Likewise, these bacteria are obligate aerobic. Due to this, to develop they must necessarily be in an environment in which there is a wide availability of oxygen.

Similarly, these bacteria require certain conditions to develop in crops. Among these we can mention: temperature ranges that go from 25 ° C to 30 ° C, as well as a pH between 5.4 and 6.3.

Regarding their biochemical characteristics, it can be said that bacteria of the genus Acetobacter are catalase positive. This implies that they are capable of synthesizing the enzyme catalase, through which they can degrade the hydrogen peroxide molecule to water and oxygen.

In the same vein, Acetobacter are oxidase negative, since they do not have the ability to synthesize any of the enzymes of the group of cytochrome c oxidases.

This group of bacteria is highly appreciated commercially, as they can carry out acetic fermentation, the end product of which is acetic acid, also known as vinegar. Likewise, in other processes they can oxidize compounds such as lactate and acetate to carbon dioxide and water.

These bacteria are considered non-pathogenic. They are totally innocuous for humans, so they do not generate any type of pathologies at an organic level.

Morphology

Bacterial cells of the genus Acetobacter have a varied shape, they can be straight or slightly curved rods or they can also have an ellipsoidal or ovoid shape. These cells are approximately 0.6-0-8 microns wide by 1.0-4.0 microns long.

In the same way, these bacterial cells are not surrounded by a capsule and they do not produce spores, so they lack that defense mechanism when environmental conditions become hostile.

These bacteria have extensions known as flagella on their cell surface. In some species the flagella are peritric and in others they are polar.

Likewise, these bacteria can be found individually, in pairs or in chains. Chains tend to be short.

When grown in the laboratory, these bacteria produce colonies that are generally pale, as they do not synthesize pigments. However, there are some species that do produce them and give rise to brown or pink colonies.

Habitat

These bacteria are distributed throughout the globe, occupying various habitats and ecological niches. They can be found in vegetation; on the flowers, some fruits and on the garden soil.

Likewise, they can also be associated with bacteria that are fermenters, which can be found in flowers and fruits, in the soil, in water and even in bee panels.

Main species

Acetobacter is a genus that encompasses a large number of species (more than 18). The most representative species of the genus are described below.

Acetobacter aceti

This bacterium was first described in 1864 by the famous French scientist Louis Pasteur, who determined that it is responsible for the formation of vinegar through the process known today as acetic fermentation.

Acetobacter aceti is a rod-shaped bacteria found in pairs or chains, as well as individually. Likewise, they present pertricular flagella, which can rotate clockwise or counterclockwise.

This is a bacterium that can resist high levels of acidity and is strictly aerobic. As a product of its metabolism it can produce alcohol. Likewise, it uses alcohol and some carbohydrates as a source of carbon, to finally obtain acetic acid.

From a commercial point of view, this bacterium is extremely important, since it is used in the production of vinegar through the acetic fermentation process.

Acetobacter cerevisiae

This species is relatively new, since it was described for the first time only in 2012. In cultures it develops colonies whose color ranges from beige to brown. They are round in shape and slightly raised.

It shares many of its characteristics with the other species of the genus Acetobacter. Among these, it can be mentioned that they are oxidase negative and catalase positive. Likewise, it is known to grow efficiently on ethanol, glucose, and glycerol, as well as organic acids. Through its metabolism it obtains as its main products compounds such as ethyl acetate and dihydroxyacetone, among others.

In addition, this bacterium is known to be very sensitive to very low pH levels and can survive low oxygen levels. Likewise, the optimum temperature at which it develops ranges between 20 ° C and 25 °

Acetobacter oeni

It is a bacterium belonging to the Acetobacter genus, the so-called vinegar bacteria. They are cells that are rod-shaped and measure approximately 0.8 - 0.9 microns wide by 3.6-5.1 microns long.

Its optimum growth temperature is 28 ° C. You can also use ethanol and methanol as carbon sources.

Like many bacteria of this genus, the main habitat in which Acetobacter oeni is found is one in which sugars such as fruits and flowers are widely available.

Despite sharing many of its characteristics with the rest of bacteria of the same genus, Acetobacter oeni has certain distinctive characteristics. Among these it can be mentioned that they produce -5-keto-D-gluconic acid, and that they are capable of growing in ethanol at a concentration of 10%.

Other species

The genus Acetobacte r is very broad and includes some species that, under conditions of immunosuppression, can cause pathologies in man. These bacteria include Acetobacter indonesiensis, which has been isolated from patients with pneumonia.

Likewise, there are other bacteria that are used in the wine and vinegar industry such as Acetobacter lovaniensis, Acetobacter orleanensis and Acetobacter Pasteurianus, among many others.

References

1. Köning, H., Unden, G. and Frölich, J. (2009). Biology of microorganism on grapes, in must and in wine. Springer, New York
2. Kouser, J., Uddin, M. and Gulzarul, M. (2016) Isolation and characterization of Acetobacter aceti from rottem papaya. Retrieved from: researchgate.net
3. Kretova, Miroslava. (2005). Characterization and identification of Acetobacter Chemicke listy. 99 (2) 144-149
4. Madigan, M. and Martinki, J. (2005) Brock Biology of Microorganisms. Prentice Hall. 11th edition
5. Ray, B. and Bhunia, A. Fundamentals of food microbiology. Mc Graw and Hill. 4th edition. Mexico