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The Effects of Temperature on Gram-Positive Bacteria

Several environmental factors influence bacterial growth, including temperature, pH, salt concentrations, sunlight and nutrient availability. The Gram-staining procedure is a technique to identify strains of bacteria, based on the cells' ability to stain either purple or pink. Gram-positive bacteria are sensitive to fluctuations of temperature, as are other bacteria. This sensitivity can influence the production of toxins, colony formation, replication and growth.

  1. Quorum Sensing

    • Quorum sensing is a phenomenon in which bacterial cells secrete molecules used to communicate with one another to regulate growth. A March 2010 article in "FEMS Microbiology Review" investigated the effects of temperature on quorum sensing in Gram-positive bacteria. Researchers used a strain of bacteria, Bacillus subtilis, to analyze the effects of temperature and other parameters on the secretion of the signaling molecules, called kinases. The study found that temperature as well as pH and nutrients all contribute to the release of kinases that, in turn, regulate the development of bacterial quorum sensing.

    Pili Development

    • The outer coverings of bacterial cells often have hair-like structures, called pili, that are responsible for motion and signaling of the microorganisms. A September 2010 article in "Microbiology" evaluated the effects of temperature on the development of pili on Gram-positive bacteria. The study found that strains of Enterococcus faecium grew pili at 37 degrees Centrigrade, or body temperature. At 21 degrees Centrigrade, however, the bacterial still developed pili, but they were anchored to the cell wall as opposed to the cellular envelope. The authors concluded that temperature influences the development of pili of bacterial cells.

    Food Spoilage

    • A strain of Gram-positive bacteria, called Bacillus cereus, is known as a pyschrotropic species ---  one that grows well in cooler climates. An article in the June 2010 issue of "Food Microbiology" analyzed the effects of temperature on B. cereus collected from a farm and six egg facilities during a period of warm and cool weather to evaluate the frequency of egg spoilage. The researchers tested temperatures ranging from 6 degrees Centigrade to 43 degrees Centigrade, and found that B. cereus grown at 10 degrees Centrigrade or above was toxic to the eggs, due to the ability of bacteria to form aggregates of cells that increase the likelihood of survival.

    Food Poisoning

    • Gram-positive bacteria of the genus Staphylococcal have the ability to produce a toxin, called Staphylococcal enterotoxin D (SED), which causes food poisoning. A May 2011 article in "Food Microbiology" investigated the effects of temperature on the spoilage of ham products due to the production of this toxin. The researchers used samples from three types of ham --- boiled, smoked and dry-cured --- that were left out at room temperature for seven days. The study found that boiled and smoked ham had constantly rising levels of the SED toxin over the trial, but dry-cured ham had as little as one-ninth of that seen in the others. After five days, all hams had high-enough levels of the SED toxin to cause food poisoning. This result indicated that processing temperatures did little to influence SED toxin levels that can cause illness.

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