Lactobacillus is a genus of Gram-positive, facultative anaerobic or
microaerophilic, rod-shaped, non-spore-forming bacteria. They are a
major part of the lactic acid bacteria group (i.e. they convert sugars
to lactic acid). In humans, they constitute a significant component of
the microbiota at a number of body sites, such as the digestive
system, urinary system, and genital system. In women of European
Lactobacillus species are normally a major part of the
Lactobacillus forms biofilms in the
vaginal and gut microbiota, allowing them to persist during harsh
environmental conditions and maintain ample populations.
Lactobacillus exhibits a mutualistic relationship with the human body
as it protects the host against potential invasions by pathogens, and
in turn, the host provides a source of nutrients.
the most common probiotic found in food such as yogurt, and it is
diverse in its application to maintain human well-being as it can help
treat diarrhea, vaginal infections and skin disorders such as
4 Human health
4.1 Vaginal tract
4.2 Interactions with other pathogens
4.4 Oral health
5 Food production
6 See also
8 External links
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Many lactobacilli operate using homofermentative metabolism (they
produce only lactic acid from sugars), and some species use
heterofermentative metabolism (they can produce either alcohol or
lactic acid from sugars). They are aerotolerant despite the
complete absence of a respiratory chain. This aerotolerance is
manganese-dependent and has been explored (and explained) in
Lactobacillus plantarum. Many species of this genus do not require
iron for growth and have an extremely high hydrogen peroxide
Tryptophan metabolism by human gastrointestinal microbiota (v · t ·
↓Activation of glial cells and astrocytes
–Inhibits β-amyloid fibril formation
Maintains mucosal reactivity:
Associated with vascular disease:
Smooth muscle cell
Smooth muscle cell proliferation
↑Aortic wall thickness and calcification
Associated with chronic kidney disease:
This diagram shows the biosynthesis of bioactive compounds (indole and
certain other derivatives) from tryptophan by bacteria in the gut.
Indole is produced from tryptophan by bacteria that express
Clostridium sporogenes metabolizes tryptophan into
indole and subsequently
3-indolepropionic acid (IPA), a highly
potent neuroprotective antioxidant that scavenges hydroxyl
radicals. IPA binds to the pregnane X receptor (PXR) in
intestinal cells, thereby facilitating mucosal homeostasis and barrier
function. Following absorption from the intestine and distribution
to the brain, IPA confers a neuroprotective effect against cerebral
ischemia and Alzheimer’s disease.
metabolize tryptophan into indole-3-aldehyde (I3A) which acts on the
aryl hydrocarbon receptor (AhR) in intestinal immune cells, in turn
increasing interleukin-22 (IL-22) production.
triggers the secretion of glucagon-like peptide-1 (GLP-1) in
intestinal L cells and acts as a ligand for AhR.
Indole can also
be metabolized by the liver into indoxyl sulfate, a compound that is
toxic in high concentrations and associated with vascular disease and
renal dysfunction. AST-120 (activated charcoal), an intestinal
sorbent that is taken by mouth, adsorbs indole, in turn decreasing the
concentration of indoxyl sulfate in blood plasma.
The genomes of
Lactobacillus are highly variable, ranging in size from
1.2 to 3.3 Mb (megabases). Accordingly, the number of protein-coding
genes ranges from 1,100 to about 3,200 genes.
Lactobacillus contains a wealth of compound microsatellites in the
coding region of the genome, which are imperfect and have variant
Lactobacillus currently contains over 180 species and
encompasses a wide variety of organisms. The genus is
polyphyletic, with the genus
Pediococcus dividing the L. casei group,
and the species L. acidophilus, L. salivarius, and
L. reuteri being
representatives of three distinct subclades. The genus
Paralactobacillus falls within the
L. salivarius group. In recent
years, other members of the genus
Lactobacillus (formerly known as the
Leuconostoc branch of Lactobacillus) have been reclassified into the
genera Atopobium, Carnobacterium, Weissella, Oenococcus, and
Leuconostoc. More recently, the
Pediococcus species P. dextrinicus has
been reclassified as a
Lactobacillus species. According to
Lactobacillus species can be divided into three groups:
Obligately homofermentative (group I) including:
L. acidophilus, L. delbrueckii, L. helveticus, L. salivarius
Facultatively heterofermentative (group II) including:
L. casei, L. curvatus, L. plantarum, L. sakei
Obligately heterofermentative (group III) including:
L. brevis, L. buchneri, L. fermentum, L. reuteri
The female genital tract is one of the principal colonisation sites
for human microbiota, and there is interest in the relationship
between the composition of these bacteria and human health, with a
domination by a single species being correlated with general welfare
and good outcomes in pregnancy. In around 70% of women, a
Lactobacillus species is dominant, although that has been found to
vary between American women of European origin and those of African
origin, the latter group tending to have more diverse vaginal
microbiota. Similar differences have also been identified in
comparisons between Belgian and Tanzanian women.
Interactions with other pathogens
Lactobacillus species produce hydrogen peroxide which inhibits the
growth and virulence of the fungal pathogen
Candida albicans in vitro
and in vivo.
In vitro studies have also shown that
Lactobacillus sp. reduce the pathogenicity of C. albicans through the
production of organic acids and certain metabolites. Both the
presence of metabolites, such as sodium butyrate, and the decrease in
environmental pH caused by the organic acids reduce the growth of
hypha in C. albicans, which reduces its pathogenicity.
Lactobacillus sp. also reduce the pathogenicity of C. albicans by
reducing C. albicans biofilm formation.
Biofilm formation is
reduced by both the competition from
Lactobacillus sp., and the
formation of defective biofilms which is linked to the reduced hypha
growth mentioned earlier. On the other hand, following antibiotic
therapy, certain Candida species can suppress the regrowth of
Lactobacillus sp. at body sites where they cohabitate, such as in the
In addition to its effects on C. albicans,
Lactobacillus sp. also
interact with other pathogens. For example,
Lactobacillus reuteri can
inhibit the growth of many different bacterial species by using
glycerol to produce the antimicrobial substance called reuterin.
Another example is
Lactobacillus salivarius, which interacts with many
pathogens through the production of salivaricin B, a bacteriocin.
Lactobacillus species administered in combination with other
probiotics benefits cases of irritable bowel syndrome (IBS), although
the extent of efficacy is still uncertain. The probiotics help
treat IBS by returning homeostasis when the gut microbiota experiences
unusually high levels of opportunistic bacteria. In addition,
Lactobacillus species can be administered as probiotics during cases
of infection by the ulcer-causing bacterium Helicobacter pylori.
Helicobacter pylori is linked to cancer, and antibiotic resistance
impedes the success of current antibiotic-based eradication
Lactobacillus probiotics are administered along
with the treatment as an adjuvant, its efficacy is substantially
increased and side effects may be lessened. Also,
used to help control urogenital and vaginal infections, such as
bacterial vaginosis (BV).
Lactobacillus produce bacteriocins to
suppress pathogenic growth of certain bacteria, as well as lactic
acid and H2O2 (hydrogen peroxide).
Lactic acid lowers the vaginal pH
to around 4.5 or less, hampering the survival of other bacteria, and
H2O2 reestablishes the normal bacterial flora and normal vaginal
pH. In children,
Lactobacillus strains such as L. rhamnosus are
associated with a reduction of atopic eczema, also known as
dermatitis, due to anti-inflammatory cytokines secreted by this
Lactobacillus species have been associated with cases of dental
Lactic acid can corrode teeth, and the
Lactobacillus count in saliva has been used as a "caries test" for
many years. Lactobacilli characteristically cause existing carious
lesions to progress, especially those in coronal caries. The issue is,
however, complex, as recent studies show probiotics can allow
beneficial lactobacilli to populate sites on teeth, preventing
streptococcal pathogens from taking hold and inducing dental decay.
The scientific research of lactobacilli in relation to oral health is
a new field and only a few studies and results have been
published. Some studies have provided evidence of certain
Lactobacilli which can be a probiotic for oral health. Some
species, but not all, show evidence in defense to dental caries.
Due to these studies, there have been applications of incorporating
such probiotics in chewing gum and lozenges. There is also
evidence of certain Lactobacilli that are beneficial in the defense of
periodontal disease such as gingivitis and periodontitis.
Lactobacillus species are used as starter cultures in industry
for controlled fermentation in the production of yogurt, cheese,
sauerkraut, pickles, beer, cider, kimchi, cocoa, kefir, and other
fermented foods, as well as animal feeds. The antibacterial and
antifungal activity of
Lactobacillus species rely on production of
bacteriocins and low molecular weight compounds that inhibits these
Sourdough bread is made either spontaneously, by taking advantage of
the bacteria naturally present in flour, or by using a "starter
culture", which is a symbiotic culture of yeast and lactic acid
bacteria growing in a water and flour medium. The bacteria metabolize
sugars into lactic acid, which lowers the pH of their environment,
creating a signature "sourness" associated with yogurt, sauerkraut,
In many traditional pickling processes, vegetables are submerged in
brine, and salt-tolerant
Lactobacillus species feed on natural sugars
found in the vegetables. The resulting mix of salt and lactic acid is
a hostile environment for other microbes, such as fungi, and the
vegetables are thus preserved—remaining edible for long periods.
Lactobacilli, especially L. casei and L. brevis, are some of the most
common beer spoilage organisms. They are, however, essential to the
production of sour beers such as Belgian lambics and American wild
ales, giving the beer a distinct tart flavor.
Lactobacillus L. anticaries
Lactic acid fermentation
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Lactobacillus spp. convert tryptophan to
indole-3-aldehyde (I3A) through unidentified enzymes .
Clostridium sporogenes convert tryptophan to IPA , likely via a
tryptophan deaminase. ... IPA also potently scavenges hydroxyl
Table 2: Microbial metabolites: their synthesis, mechanisms of action,
and effects on health and disease
Figure 1: Molecular mechanisms of action of indole and its metabolites
on host physiology and disease
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IPA metabolism diagram
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neurons and neuroblastoma cells exposed to the amyloid beta-protein in
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features of Alzheimer's disease.
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Origin: • Endogenous • Microbial
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Data related to
Lactobacillus at Wikispecies
List of species of the genus Lactobacillus
Lactobacillus at Milk the Funk Wiki
Lactobacillus at BacDive - the Bacterial Diversity Metadatabase
Lactobacillus delbrueckii subsp. bulgaricus
Fermented milk products
Bacteria classification (phyla and orders)
Source: Bergey's Manual (2001–2012). Alternative views: Wikispecies.
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