Habitat of Lactobacillus Thermophilus

Studies have shown in the past,  that a routine bacteriological analyses of milk supply was taken and it was noticed that there was a higher bacterial count, (more bacteria), in the pasteurized milk from a local facility, than there was in the raw milk that was brought to the facility.  Cultures were made and tests were run; they found that with platings made and incubated at 37 degrees celcius and more at 50 degrees celcius, every sample of the pasteurized milk showed pinpoint colony growth of bacteria in varying numbers.  The plates at 50 degrees celcius had larger colonies and more productive growth than that of the 37 degree plates, showing distinct colonies averaging 0.8 millimeters in diameter.  When observed closely, it was noticed that these milk cultures revealed rod forms of bacteria.  When word got out, it was admitted that a peculiar flavor and a slight odor were produced by the pasteurized milk, (later linked to the lactic acid produced by the bacteria).  They called the Bacteria, Lactobacillus Thermophilus.

Lactobacillus Thermophilus has been noted to grow in both broth cultures and milk cultures. 

The broth culture being referred to is Lysogeny Broth.  It is a nutritionally rich medium used for the culturing of bacteria in tests, and is also referred to as Luria Broth, or Luria-Bertani Broth.  Slight growth was noted in the broth cultures.  They experimented with adding Peptone to the broth, a required nutrient, and saw that plentiful growth took place. 

More detail can be seen and discussed about Peptone on the Nutrition Requirements page

As seen above, Lactobacillus Thermophilus lives well in Milk Culturesthat have been made sterile by heating at 70 degrees celcius.

Optimal Growth temperatures range from 50 to 60 degrees celcius.  But be this as it may, Lactobacillus is a heat resistant bacteria, so though it may not continue to grow, it will certainly not die away at temperatures reaching 180 degrees.  The minimum or least temperature that will supply adequate growth is 37 degrees celcius.

Lactobacillus Thermophilus produces Lactic Acid.  Lactic Acid is another term for milk acid.This means that it is an acidic bacteria and therefore, prefers acidic environments.  Anything with a pH lower than 7 qualifies as acidic, but optimum conditions would stand to be 6.0.  Any cultures with a pH of 6.2 or above have failed to provide growth of the specimen.

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