Streptococcus salivarius subsp. thermophilus
Encyclopedia
Streptococcus salivarius subsp. thermophilus (previous name Streptococcus thermophilus) is a Gram-positive
bacteria and a homofermentative facultative anaerobe
, of the viridans
group. It tests negative for cytochrome
, oxidase
and catalase
, and positive for alpha-hemolytic activity. It is non-motile and does not form endospores.
It is also classified as a lactic acid bacterium
. S. thermophilus is found in fermented milk products. It is not a probiotic
(it does not survive the stomach in healthy humans) and is generally used in the production of yogurt, alongside Lactobacillus delbrueckii subsp. bulgaricus. The two species are synergistic, and S.s. thermophilus probably provides L.d. bulgaricus with folic acid
and formic acid
which it uses for purine
synthesis.
, includes some pathogenic species, food industries consider S.s. thermophilus a safer bacterium than many other Streptococcus species. In fact, yogurt and cheese that contain live cultures of S.s. thermophilus are thought to be beneficial to health. Live cultures of S.s. thermophilus make it easier for people who are lactose-intolerant to digest dairy products. The bacteria break down lactose
, the sugar in milk that lactose-intolerants find difficult to digest.
destroys these beneficial organisms. Nonetheless, S.s. thermophilus is required by law to be present in yogurt. 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 yoghurt.
When the S.s. thermophilus species diverged from its pathogenic relatives, it lost most of the genes acknowledged as being responsible for virulence. The species may have lost these genes because it adapted to a new, dairy-producing, environment in which it did not need these genes anymore.
Genome
analysis has also shown that by adapting to dairy production, the species has acquired genes that its pathogenic cousins do not have. For example, S.s. thermophilus can use the energy in lactose to help itself grow.
and a strain of S.a. thermophilus. These bacteria are chosen because they produce exopolysaccharide
(EPS) which give reduced-fat cheese a similar texture and flavor as regular cheese. However, cheese made from L. lactis yielded a different type of cheese from S.a. thermophilus.
L. lactis produced cheese with higher moisture levels compared to other reduced-fat cheeses. On the other hand, S.s. thermophilus produced low moisture cheese and decreased the bitterness of cheese. It had been concluded that applying both L. lactis and S.s. thermophilus strains create higher quality reduced-fat cheese with similar characteristics to regular cheese.
often causes mucositis
, severe inflammation
of primarily the small intestines. Currently, there is no treatment to alleviate the symptoms of mucositis caused by chemotherapy. When rats were inflicted with mucositis by chemotherapy drugs, cells in the infected areas functioned more healthily and the tissue was less distressed. In her nutrition book, Jean Carper describes an experiment by Dr Joseph A Scimeca, in which commercially-available yoghurt containing Ss.. thermophilus and L.d. bulgaricus was fed to mice. After these mice were injected with cancer cells, the incidence of lung cancer
in the yoghurt-fed mice was one-third less than expected.
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...
bacteria and a homofermentative facultative anaerobe
Facultative anaerobic organism
A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation...
, of the viridans
Streptococcus viridans
Viridans Streptococcus is a pseudotaxonomic non-Linnaenan term for a large group of commensal streptococcal bacteria that are either α-hemolytic, producing a green coloration on blood agar plates , or nonhemolytic...
group. It tests negative for cytochrome
Cytochrome
Cytochromes are, in general, membrane-bound hemoproteins that contain heme groups and carry out electron transport.They are found either as monomeric proteins or as subunits of bigger enzymatic complexes that catalyze redox reactions....
, oxidase
Oxidase
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
and catalase
Catalase
Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...
, and positive for alpha-hemolytic activity. It is non-motile and does not form endospores.
It is also classified as a lactic acid bacterium
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...
. S. thermophilus is found in fermented milk products. It is not a probiotic
Probiotic
Probiotics are live microorganisms thought to be beneficial to the host organism. According to the currently adopted definition by FAO/WHO, probiotics are: "Live microorganisms which when administered in adequate amounts confer a health benefit on the host"...
(it does not survive the stomach in healthy humans) and is generally used in the production of yogurt, alongside Lactobacillus delbrueckii subsp. bulgaricus. The two species are synergistic, and S.s. thermophilus probably provides L.d. bulgaricus with folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
and formic acid
Formic acid
Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...
which it uses for purine
Purine
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
synthesis.
Uses
S.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 yoghurt were produced from S.s. thermophilus. Although its genus, StreptococcusStreptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
, includes some pathogenic species, food industries consider S.s. thermophilus a safer bacterium than many other Streptococcus species. In fact, yogurt and cheese that contain live cultures of S.s. thermophilus are thought to be beneficial to health. Live cultures of S.s. thermophilus make it easier for people who are lactose-intolerant to digest dairy products. The bacteria break down lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...
, the sugar in milk that lactose-intolerants find difficult to digest.
Yogurt production
As long ago as the early 1900s, S.s. thermophilus has been used to make yogurt. Many of the yogurts sold in grocery stores today do not contain many live cultures of S.s. thermophilus because pasteurizationPasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
destroys these beneficial organisms. Nonetheless, S.s. thermophilus is required by law to be present in yogurt. 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 yoghurt.
Nomenclature
Streptococcus derives from a Greek term meaning "twisted berry" and refers to the way the bacterium is grouped in chains that resemble a string of beads. "Thermophilus" derives from the Greek term thermotita meaning "heat". It refers to an organism's ability to thrive at high temperatures.Pathogenic potential
The genus Streptococcus includes several pathogenic species, such as S. pneumoniae and S. pyogenes, but food industries consider S.s. thermophilus non-pathogenic. S.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.s. thermophilus, CNRZ1066 and LMG13811, and stated that the bacteria are not dangerous.When the S.s. thermophilus species diverged from its pathogenic relatives, it lost most of the genes acknowledged as being responsible for virulence. The species may have lost these genes because it adapted to a new, dairy-producing, environment in which it did not need these genes anymore.
Genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
analysis has also shown that by adapting to dairy production, the species has acquired genes that its pathogenic cousins do not have. For example, S.s. thermophilus can use the energy in lactose to help itself grow.
Reduced-fat cheese
S.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 lactisLactococcus lactis
Lactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has recently also become famous as the first genetically modified organism to be used alive for the treatment of human disease. L...
and a strain of S.a. thermophilus. These bacteria are chosen because they produce exopolysaccharide
Exopolysaccharide
Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharides including intracellular polysaccharides, structural...
(EPS) which give reduced-fat cheese a similar texture and flavor as regular cheese. However, cheese made from L. lactis yielded a different type of cheese from S.a. thermophilus.
L. lactis produced cheese with higher moisture levels compared to other reduced-fat cheeses. On the other hand, S.s. thermophilus produced low moisture cheese and decreased the bitterness of cheese. It had been concluded that applying both L. lactis and S.s. thermophilus strains create higher quality reduced-fat cheese with similar characteristics to regular cheese.
Cancer
ChemotherapyChemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
often causes mucositis
Mucositis
Mucositis is the painful inflammation and ulceration of the mucous membranes lining the digestive tract, usually as an adverse effect of chemotherapy and radiotherapy treatment for cancer. Mucositis can occur anywhere along the gastrointestinal tract, but oral mucositis refers to the particular...
, severe inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of primarily the small intestines. Currently, there is no treatment to alleviate the symptoms of mucositis caused by chemotherapy. When rats were inflicted with mucositis by chemotherapy drugs, cells in the infected areas functioned more healthily and the tissue was less distressed. In her nutrition book, Jean Carper describes an experiment by Dr Joseph A Scimeca, in which commercially-available yoghurt containing Ss.. thermophilus and L.d. bulgaricus was fed to mice. After these mice were injected with cancer cells, the incidence of lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
in the yoghurt-fed mice was one-third less than expected.