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Requirements for Bacterial Growth

Bacteria need certain things to grow. The most important factors are physical environment, such as temperature, oxygen, acidity and water concentration, and nutrition.

  1. Temperature

    • Bacteria can be grouped according to the range of temperature they prefer. Psychrophiles grow best from -5 C to 15C in Arctic and Antarctic environments, mesophiles in the soil and the human body (most bacteria) prefer 25 C to 45 C, thermophiles in hot springs like 45 C to 70 C, and hyperthermophiles grow best in thermal vents in the ocean from 70 C to 110 C.

    Oxygen Requirements

    • Most bacteria are obligate aerobes. They require oxygen in different concentrations, depending on the species. Obligate anaerobes cannot grow in oxygen. Then there are bacteria which can survive with or without oxygen, but may prefer one to the other.

    Acidity

    • Bacteria are divided into several groups based on their preferred range of acidity (pH). Neutrophiles do best at a pH of 5 to 8. Acidophiles prefer a level below 5.5, which is higher acid. Allaliphiles prefer a level above 8.5, which is basic.

    Water Concentration

    • Most bacteria prefer an isotonic (water and salt concentration are the same within the cell and outside the cell) or hypotonic environment (more water inside cell, more salts outside).

    Nutritional Requirements

    • Bacteria need nutrients, usually carbon (from organic sources or carbon dioxide gas, for example) and minerals like sulfur, phosphorus, potassium, magnesium, calcium, iron, and trace elements. Water, amino acids and vitamins are also needed. Bacteria commonly use light to convert nutrients to energy. However, there are also bacteria that can use sulfur, hydrogen gas, ammonia or iron instead of light to do this.

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