Lactobacillaceae
Lactobacillus sp.
Lactobacillaceae form a family of Gram-positive bacteria of the order Lactobacillales. Through fermentation to produce lactic acid and are therefore among the lactic acid bacteria, including several more families will be provided, which are combined in the system in the order of Lactobacillales. Many species of this family are important for the food industry. They are used for the manufacture of dairy products, but can also occur as pests ( eg in the brewery ). The people they usually add to any harm, they are non-pathogenic.
In the family Lactobacillaceae are currently (2013 ) summarized three genera: the lactobacilli (Lactobacillus ), the pediococci ( Pediococcus ) and Sharpea. The latter contains only one species with Sharpea azabuensis The type Paralactobacillus selangorensis Leisner et al. 2000 is now listed as a synonym of Lactobacillus selangorensis. Previously also still included the genera Oenococcus, Carnobacterium, Weissella and Leuconostoc to the family of Lactobacillaceae. Previously the type Bifidobacterium bifidum was provided to the genus Lactobacillus ( German lactobacilli) in the family Lactobacillaceae (Lactobacillus bifidum ), in the current situation it is not phylogenetically with the order in the near connection. Concerning the metabolism but it is still treated as a lactic acid bacterium.
- 6.1 Notes and references
- 6.2 Literature
Features
The species are gram-positive bacteria, they never form spores and are usually immobile. Cells of Pediococcus species are occurring in pairs or tetrads cocci. The species of Lactobacillus are rod-shaped, but also curved and helical (eg Lactobacillus curvatus ) variations may occur. The type Sharpea azabuensis the cells are also rod-shaped, they occur in chains.
The species are catalase - negative and oxidase - negative. Like most lactic acid bacteria tolerate in their environment only small amounts of oxygen. Many representatives of the Lactobacillaceae grow anaerobically, but aerotolerant, ie they grow in the presence of atmospheric oxygen, but does not need it for their metabolism. In Lactobacillus, however there are also some species that tolerate absolutely no oxygen ( obligate anaerobes ). Sharpea azabuensis also grows only under strictly anaerobic conditions.
Many types of Lactobacillaceae form bacteriocins kill toxic proteins or peptides that are secreted by bacteria and other ( competing) species of bacteria or hinder growth. Bacteriocins, which are formed of different Lactobacillus species are i.a. Lactacin -F -A and Bavaricin. Lactobacillus plantarum is different Planta ricins (A, S, T, and Planta ricin SIK ). Of the pediococci et al Pediocine be formed.
Occurrence
Except in milk and dairy products come before representatives of the Lactobacillaceae in or on plants. Some form part of the natural intestinal flora of humans and other animals, so Sharpea azabuensis was isolated from the faeces of a thoroughbred horse. Lactobacilli were isolated from all parts of the digestive tract of humans, including the stomach.
Pediococcus species, also known as Pediococcus, were found for the most part in or on plants and fruits ( phyllosphere ). Especially with plants in the state, the fermenting Pediococcus reach a large amount. In other habitats they were found less frequently. For example, some types of Pediococcus from human feces, Pediococcus acidilactici and Pediococcus parvulus were isolated from the feces of healthy turkeys. Pediococcus acidilactici was also found in the intestine of carp ( Cyprinus carpio) and in the shrimp Macrobrachium rosenbergii species.
Lactic acid fermentation
A distinction is made between homofermentative and heterofermentative species. Homofermentative species produce by fermentation almost exclusively lactic acid, while heterofermentative species besides lactic acid produce a significant proportion of other end products, mostly ethanol and carbon dioxide. The heterofermentative usually lack the enzyme aldolase. All kinds of Pediococcus are homofermentative, in Lactobacillus find both homo-and heterofermentative species. Lactobacillus species are usually resistant against low pH values than the other lactic acid bacteria, and to grow at a pH of 4 to 5
System
In this family are currently (2013 ) summarized three genera: Lactobacillus, Pediococcus and Sharpea. The majority of the species can be found in Lactobacillus (around 80) of Sharpea is only one type known Sharpea azabuensis. The 2000- discovered genus Paralactobacillus with the way Paralactobacillus selangorensis had also been assigned to the Lactobacillaceae family, later studies showed, however, that it is in fact a kind within the genus Lactobacillus. In 2011, therefore, was renamed Lactobacillus selangorensis.
The taxonomic position of Pediococcus dextrinicus was under discussion due to some differences in the metabolism of the other species. It is the only species of the genus, fermented starch and produces CO2 and seems phylogenetically more of the other pediococci to be removed ( the so-called "true Pediococci "). Also, molecular genetic studies indicate. Because of the conversion took place in 2009 to the genus Lactobacillus, having an extended description of the genus Lactobacillus. Another special feature of this type is the production of L-( )- lactic acid ( dextrorotatory lactic acid). Just another type of Pediococcus Pediococcus claussenii makes this metabolite, the remaining species form a racemate of right-and left -turning lactic acid (DL -lactate ).
A selection of the types of Pediococcus:
- Pediococcus Claussen 1903 Pediococcus acidilactici Lindner 1887
- Pediococcus celli cola Zhang et al. 2005
- Pediococcus ethanolidurans Liu et al. 2006
- Pediococcus inopinatus Back 1988
- Pediococcus pentosaceus Mees 1934
The best in saline environments growth rates achieved ( halophilic ) Type Pediococcus halophilus was placed in the genus Tetragenococcus (now so Tetragenococcus halophilus ), in the family of Enterococcaceae that belongs as the family Lactobacillaceae to order Lactobacillales.
Relevance to humans
As beneficial
The lactic acid fermentation is used in the food industry, especially in the production of milk products such as cheese and yogurt. Without lactobacilli, there would be virtually no dairy products. But also in the production of other leavened food and feed they are involved.
Some types and their use ( mostly are still other types of bacteria mitbeteiligt ):
- Silage: The production of silage in the agricultural sector, Pediococcus pentosaceus and using Lactobacillus plantarum.
- Sauerkraut: Here different kinds of Lactobacillus ( L. plantarum v. a ) are used to the other participating genera Leuconostoc counts among others.
- Sourdough: The sourdough made with rye flour contains, inter alia, Lactobacillus plantarum, L. brevis and L. coryniformis and yeasts (Saccharomyces cerevisiae, Saccharomyces minor). Made with wheat flour sourdough - so-called wheat sour - will in most cases Lactobacillus sanfranciscensis, L. plantarum and Weissella confusa, these species are introduced through the flour. Other lactobacilli, which have been found in studies of leaven are L. rossiae, L. brevis, and as more lactic acid bacteria Lactococcus lactis subsp. lactis, and Pediococcus pentosaceus.
- Sour milk: Initial here mesophilic streptococcal cultures were used, but also the use of Lactobacillus species, especially Lactobacillus acidophilus is common. The sour milk product prepared in this manner is characterized by a milder taste. It was sold under the names " acidophilus milk " or " Bioghurt " increasingly popular with the German consumer. According to the Regulation on dairy products this product is referred to as " mild yoghurt " and thus complements the product range with yogurt.
- Yogurt: In the production of traditional yoghurt Lactobacillus delbrueckii subsp. bulgaricus ( in this context in the literature usually referred to as Lactobacillus bulgaricus ) - Streptococcus salivarius in combination with subsp. thermophilus (Streptococcus thermophilus ) - specifically used as a starter culture. Since the bacteria used well proliferate at 43-45 ° C, they are referred to in the dairy as thermophilic Säuerungskulturen.
- Cheese: In addition to mesophilic Säuerungskulturen ( esp. Lactococcus and Leuconostoc species) are also more likely to thermophilic species of Lactobacillus, such as Lactobacillus helveticus and Lactobacillus delbrueckii subsp. lactis used. Also see L. casei and L. delbrueckii subsp. bulgaricus use.
- Raw sausage: For the production of raw sausage, such as salami, are the types Pediococcus acidilactici and P. pentosaceus, of the lactobacilli L. curvatus and L. sakei as starter cultures by Pediococcus mainly. Other genera of bacteria that are used in starter cultures are staphylococci ( eg, Staphylococcus carnosus and S. xylosus ) and Kocuria varians (formerly Micrococcus varians ).
- In the manufacture of some types of beer as the Berliner Weisse different types Lactobacillus are used together with yeasts.
When pests
Species of Lactobacillus and Pediococcus are known as pests in the beverage production. The formation of lactic acid and other products leads to an undesirable change in taste and acidification, for example beer, wine and fruit juices. In the brewery can produce various kinds of Pediococcus, herein referred to as Beer sarcinse, causing considerable damage. Also, some species of Lactobacillus can spoil the beer. It caused a reduction in quality of beverages, such as change of taste, or turbidity. Species such as Pediococcus damnosus ( often referred to as P. cerevisiae ), P. pentosaceus and P. acidilactici cause by elimination of diacetyl a Gemacksveränderung. Homofermentative lactobacilli cause acidification, heterofermentative cause turbidity and change of taste brought about.
The most common pests of beer lactobacilli are Lactobacillus casei ( homofermentative ) and Lactobacillus brevis ( heterofermentative lactic acid fermentation), the Pediococcus Pediococcus damnosus. The name of the pediococci as " beer - sarcinse " refers to the Kokkenform. In the literature, related to the caused by Pediococcus beer - spoilage usually the (false ) Style Name Pediococcus cerevisiae. In the scheme of this taxon is invalid, the correct name is Pediococcus damnosus. In the literature the name Pediococcus cerevisiae but is still often found.
Other important beer spoilers are to be found in the family Acidaminococcaceae ( genus Megasphaera and Pectinatus ), others are Acetobacter, Gluconobacter and Klebsiella.
Pediococcus damnosus can also occur in the winemaking process as a pest. Furthermore, can cause in fruit juices Lactobacillus damage. Examples are the species L. casei, L. paracasei and L. perolens.