''Lentilactobacillus hilgardii'' is a species of
bacterium
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
found in
wine
Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...
, dairy products, and wine musts.
Its
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
is consistent (on a cellular level) of rods that are 0.5–0.8 micrometres of both single short chains and long filament like structures. On a colony level, the bacteria appears glossy, round and white. For study, the bacteria requires malt agar and can ferment
maltose
}
Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
, but often also requires
yeast
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
extract in order to ferment properly. To study ''L. hilgardii'' in liquid requires growing it in
Elliker broth so it can show
turbidity
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
Fluids can ...
and gas formation.
On staining with Gram's iodine, the bacillus is
Gram positive
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
Gram-positive bact ...
. ''L. hilgardii'' is considered a negative
catalase
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
(enzyme that decomposes
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%†...
into oxygen and water) and creates
lactic acid
Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ...
, ethanol/acetic acid, and
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
. Along with this it is capable of sometimes producing biogenic
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
s or
histamine
Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discovered in ...
and
ethyl carbamate
Ethyl carbamate (also called urethane) is an organic compound with the formula CH3CH2OC(O)NH2. It is an ester of carbamic acid and a white solid. Despite its name, it is not a component of polyurethanes. Because it is a carcinogen, it is rarely use ...
, which causes health risks.
Its role in the
fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
of wine is that it is impactful when spoiling high-alcohol dessert wines and can be used in malolactic fermentations (winemaking fermentation). ''Lentilactobacillus hilgardii'' is sensitive to SO
2, both not sensitive and metabolized to
sorbate
Sorbic acid, or 2,4-hexadienoic acid, is a natural organic compound used as a food preservative. It has the chemical formula and the structure . It is a colourless solid that is slightly soluble in water and sublimes readily. It was first isol ...
. It is highly tolerant to acids and pH. It is tolerant of
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
up to 20 vol%.
''Lentilactobacillus hilgardii''
hybridizes easily with ''
Levilactobacillus brevis
''Levilactobacillus brevis'' is a gram-positive, rod shaped species of lactic acid bacteria which is heterofermentative, creating CO2, lactic acid and acetic acid or ethanol during fermentation. ''L. brevis'' is the type species of the genus ''Le ...
'', a bacterium that it is very closely related to. Prior to its classification as a distinct species, ''L. hilgardii'' was believed to be ''L. brevis'', and, as a result, the bacterium's ability to hybridize raised doubts about its
taxonomy
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
.
''L. hilgardii'' grows in wine when it contains 1%
autolysed yeast. It also grows in ethanol at 15–18%. The bacteria grow best at 30–35 °C, but can grow at temperatures as low as 15 °C.
References
External links
Type strain of ''Lactobacillus hilgardii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q1967870
Lactobacillaceae
Bacteria described in 1936