It is also classified as alactic acid bacterium.[7]S. thermophilus is found in fermented milk products and is generally used in the production ofyogurt,[8] alongsideLactobacillus delbrueckii subsp.bulgaricus. The two species are synergistic, andS. thermophilus probably providesL. d. bulgaricus withfolic acid andformic acid, which it uses forpurine synthesis.[9]S. thermophilus has an optimal growth temperature range of 35–42 °C (95–108 °F), whileL. d. bulgaricus has an optimal range of 43–46 °C (109–115 °F).[10]
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 ofmozzarella cheese and 621 million kilograms of yogurt were produced fromS. thermophilus.[12] Although its genus,Streptococcus, includes some pathogenic species, food industries considerS. thermophilus a safer bacterium than many otherStreptococcus species. In fact, yogurt and cheese that contain live cultures ofS. thermophilus are thought to be beneficial to health.[13][better source needed] Live cultures ofS. thermophilus make it easier for people who arelactose-intolerant to digest dairy products. The bacteria breaks downlactose, the sugar in milk, that lactose-intolerant people find difficult to digest.[14]
As early as the 1900s,S. thermophilus was used to makeyogurt. 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.[15]
"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.[16] "Thermophilus" derives from the Greekthermē, meaning "heat", andphilus, meaning to appreciate or to like. It refers to an organism's ability to thrive at high temperatures.[17]
The genusStreptococcus includes several pathogenic species, such asS. pneumoniae andS. pyogenes, but food industries considerS. thermophilus non-pathogenic.S. thermophilus is believed to have developed separately from pathogenicStreptococcus species for at least 3000 years. Research teams have sequenced the genome of two strains ofS. thermophilus, CNRZ1066 and LMG13811, and stated that the bacteria are not dangerous.[18]
S. thermophilus strain Orla-Jensen 1919[19] is a constituent inVSL#3. This standardized formulation of live bacteria may be used in combination with conventional therapies to treatulcerative colitis.[20][21] The use of theS. thermophilus-containing VSL#3 may reduce inflammation in mice.[22]
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 ofLactococcus lactis and a strain ofS. thermophilus. These bacteria are chosen because they produceexopolysaccharide (EPS), which give reduced-fat cheese a texture and flavor like that of regular cheese.[citation needed]
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 bothL. lactis andS. thermophilus strains would create higher-quality reduced-fat cheese with characteristics like those of regular cheese.[23]
Chemotherapy often causesmucositis, severeinflammation of primarily thesmall intestines. Currently, there is no treatment to alleviate the symptoms of mucositis caused by chemotherapy. Whenrats were inflicted with mucositis by chemotherapy drugs, the intestinal tissues in those pretreated withStreptococcus thermophilus TH-4 functioned more healthily and were less distressed.[24]
Strains ofS. thermophilus have also reduced risks ofantibiotic-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 containingS. thermophilus while being treated with antibiotics had lower rates of AAD than the control group (12.4% vs. 23.7%).[25]
Streptococcus thermophilus has been linked to longevity in some living organisms. In an experiment performed on the bacteriophagous nematode speciesCaenorhabditis elegans, consumption ofS. thermophilus was shown to cause significant longevity when compared to specimens that consumedE. 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 genedaf-16. This effect further enhances the expression of other antioxidant genes, thereby slowing down the aging process.[26]
^The name appears both on Approved Lists 1980 and on Validation List No. 54 of 1995.[2] When cited as the latter, the author string would be "(ex Orla-Jensen 1919) Schleifer et al. 1995". However, the validation of a name already on the Approved Lists is an obvious error and the older citation should take precedence.[1] Nevertheless, Schleifer's 1991 "revival" article dos provide additional evidence for the species's distinctiveness.[3]
^Schleifer, Karl Heinz; Ehrmann, Mathias; Krusch, Uli; Neve, Horst (October 1991). "Revival of the Species Streptococcus thermophilus (ex Orla-Jensen, 1919) nom. rev".Systematic and Applied Microbiology.14 (4):386–388.doi:10.1016/S0723-2020(11)80314-0.
^Delcour, J.; Ferain, T.; Hols, P. (2000). "Advances in the Genetics of Thermophilic Lactic Acid Bacteria".Food Biotechnology.11 (5):497–504.doi:10.1016/s0958-1669(00)00134-8.PMID11024370.
^"Streptococcus."Encyclopædia Britannica.Encyclopædia Britannica Online. 13 April 2011.
^"Thermophile."Encyclopædia Britannica.Encyclopædia Britannica Online, 2011. 24 April 2011.
^"Streptococcus Thermophilus: A Bacterium Which Is Harmless to Health". International Research Associates. 14 November 2006. Web. 25 April 2011.
^Ripudaman S. Beniwal; Vincent C. Arena; Leno Thomas; Sudhir Narla; Thomas F. Imperiale; Rauf A. Chaudhry; Usman A. Ahmad (2003). "A Randomized Trial of Yogurt for Prevention of Antibiotic-Associated Diarrhea".Digestive Diseases and Sciences.48 (10):2077–2082.doi:10.1023/A:1026155328638.PMID14627358.S2CID23021761.
