''Streptococcus thermophilus'' also known as ''

Streptococcus salivarius ''Streptococcus salivarius'' is a species of spherical, gram-positive, facultative anaerobic lactic acid bacteria that is both catalase and oxidase negative. ''S. salivarius'' colonizes (usually in chains) the oral cavity and upper respiratory ...

''subsp.'' thermophilus'' is a gram-positive bacterium, and a fermentative

facultative anaerobe A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are '' Staphylococ ...

, of the '' viridans'' group. It tests negative for

cytochrome Cytochromes are redox-active proteins containing a heme, with a central Fe atom at its core, as a cofactor. They are involved in electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of ...

, oxidase, and

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 ...

, and positive for

alpha-hemolytic Hemolysis (from Greek αιμόλυση, meaning 'blood breakdown') is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly ...

activity. It is non-motile and does not form

endospores An endospore is a dormancy, dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore ...

. ''S. thermophilus'' is fimbriated. It is also classified as a

lactic acid bacterium Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bac ...

. ''S. thermophilus'' is found in fermented milk products and is generally used in the production of

yogurt Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as ''yogurt cultures''. Fermentation of sugars in the milk by these bac ...

, alongside ''Lactobacillus delbrueckii'' subsp. ''bulgaricus''. The two species are synergistic, and ''S. thermophilus'' probably provides ''L. d. bulgaricus'' with

folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing a ...

and

formic acid Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Est ...

, which it uses for

purine Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...

synthesis. ''S. thermophilus'' has an optimal growth temperature range of , while ''L. d. bulgaricus'' has an optimal range of .

Classification

At least 26 strains of ''S. thermophilus'' have been identified and had their genomes sequenced.

Uses

''S. thermophilus'' is one of the most widely used bacteria in the dairy industry. USDA statistics from 1998 showed that more than 1.02 billion kilograms of mozzarella cheese and 621 million kilograms of yogurt were produced from ''S. thermophilus''. Although its genus, '' Streptococcus'', includes some pathogenic species, food industries consider ''S. thermophilus'' a safer bacterium than many other ''Streptococcus'' species. In fact, yogurt and cheese that contain live cultures of ''S. thermophilus'' are thought to be beneficial to health. Live cultures of ''S. thermophilus'' make it easier for people who are

lactose-intolerant Lactose intolerance is a common condition caused by a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pa ...

to digest dairy products. The bacteria break down

lactose Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix ' ...

, the sugar in milk, that lactose-intolerant people find difficult to digest.

Yogurt production

As early as the 1900s, ''S. thermophilus'' was used to make

. Its purpose is to turn lactose, the sugar in milk, into lactic acid. The increase in lactic acid turns milk into the gel-like structure characteristic of yogurt.

Nomenclature

"Streptococcus" derives from a Greek term meaning "twisted kernel" and refers to the way the bacterium is grouped in chains that resemble a string of beads. "Thermophilus" derives from the Greek ''thermē'', meaning "heat". It refers to an organism's ability to thrive at high temperatures.

Research

Pathogenic potential

The genus ''Streptococcus'' includes several pathogenic species, such as '' S. pneumoniae'' and '' S. pyogenes'', but food industries consider ''S. thermophilus'' non-pathogenic. ''S. thermophilus'' is believed to have developed separately from pathogenic ''Streptococcus'' species for at least 3000 years. Research teams have sequenced the genome of two strains of ''S. thermophilus'', CNRZ1066 and LMG13811, and stated that the bacteria are not dangerous.

Adjuvant

''S. thermophilus'' strain Orla-Jensen 1919 is a constituent in VSL#3. This standardized formulation of live bacteria may be used in combination with conventional therapies to treat

ulcerative colitis Ulcerative colitis (UC) is a long-term condition that results in inflammation and ulcers of the colon and rectum. The primary symptoms of active disease are abdominal pain and diarrhea mixed with blood (hematochezia). Weight loss, fever, and ...

. The use of the ''S. thermophilus''-containing VSL#3 may reduce inflammation in mice.

Reduced-fat cheese

''S. thermophilus'' helps make reduced-fat cheese with similar characteristics to regular, full-fat cheese. In the experiment, two different strains of bacteria are used to make reduced-fat cheddar cheese: a strain of '' Lactococcus lactis'' and a strain of ''S. thermophilus''. These bacteria are chosen because they produce exopolysaccharide (EPS), which give reduced-fat cheese a texture and flavor like that of regular cheese. ''L. lactis'' produces cheese with higher moisture levels compared to other reduced-fat cheeses; ''S. thermophilus'' produces cheese with a lower moisture content and a less bitter taste. It was concluded that applying both ''L. lactis'' and ''S. thermophilus'' strains would create higher-quality reduced-fat cheese with characteristics like those of regular cheese.

Cancer

Chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemother ...

often causes mucositis, severe

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

of primarily the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

s. Currently, there is no treatment to alleviate the symptoms of mucositis caused by chemotherapy. When rats were inflicted with mucositis by chemotherapy drugs, the intestinal tissues in those pretreated with ''streptococcus thermophilus'' TH-4 functioned more healthily and were less distressed.

Antibiotic-associated diarrhea

Strains of ''S. thermophilus'' have also reduced risks of antibiotic-associated diarrhea (AAD), an issue that results from taking antibiotics. Antibiotics can have the adverse effect of destroying beneficial bacteria and causing harmful bacteria to multiply, which invokes AAD. Adults who ate yogurt containing ''S. thermophilus'' while being treated with antibiotics had lower rates of AAD than the control group (12.4% vs. 23.7%).

Longevity in other organisms

''Streptococcus thermophilus'' has been linked to longevity in some living organisms. In an experiment performed on the bacteriophagous nematode species ''

Caenorhabditis elegans ''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek ''caeno-'' (recent), ''rhabditis'' (r ...

'', consumption of ''S. thermophilus'' was shown to cause significant longevity when compared to specimens that consumed ''E. coli'' OP50, a strain used as a standard food source. Additionally, there was no significant deviation in growth rate or brood size, indicating that it wasn’t caused by caloric restriction. Instead, its life-extending effects were linked to increased expression of the gene ''daf-16''. This effect further enhances the expression of other antioxidant genes, thereby slowing down the aging process.

Health concerns

Although

probiotic Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host i ...

s, in general, are considered safe, there are concerns about their use in certain cases. Some people, such as those with compromised immune systems, short bowel syndrome,

central venous catheters A central venous catheter (CVC), also known as a central line(c-line), central venous line, or central venous access catheter, is a catheter placed into a large vein. It is a form of venous access. Placement of larger catheters in more central ...

, heart valve disease and premature infants, may be at higher risk for adverse events. Rarely, the use of

probiotics Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria- host i ...

has caused

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

in children with lowered immune systems or in those who are already critically ill.

References

{{Taxonbar, from=Q1041276 Gram-positive bacteria Streptococcaceae Bacteria used in dairy products Probiotics Bacteria described in 1919