Bacteria are single-celled organisms that have a variety of growth requirements. Some bacteria require oxygen; others require the absence of oxygen for growth. Bacteria that need high temperatures for growth, or thermophiles, live in environments different from psychrophiles, which require low temperatures for growth. The type of environment you observe, in many cases, can tell you exactly what type of bacteria lives there.
Human Body
The human body harbors a wide variety of bacteria of different growth types and requirements. Though the human body requires oxygen, many micro-environments in and around the body have areas where different types of bacteria can thrive. The mouth, for instance, contains a habitat of bacteria that prefers to ferment sugars for energy and needs a high water content for growth. The sugars in the mouth that the bacteria use come from foods. According to the textbook "Microbiology," written by Lansing Prescott, John Harley and Donald Klein, many bacteria that reside in the human body live in the gastrointestinal tract. These bacteria have a mutually beneficial relationship with humans. The food that is in the process of digestion gives the bacteria nutrients, while the bacteria themselves aid in essential vitamin production for the individual.
Food
Bacteria are ubiquitous in the environment and are constantly looking for a source of nutrients. Food that is left out or undercooked represents a prime area for the growth of bacteria. Not only does bacteria simply grow on foods, it is also important in the chemical conversion of food. Sauerkraut is simply shredded cabbage fermented by lactic acid producing bacteria like Lactobacillus and Leuconostoc. According to the U.S. Department of Energy, cheese varieties get produced by a number of different bacteria. The type of bacteria is often synonymous with the type of cheese that is produced.
Water
Bacteria exist in many types of aqueous environments. Lakes, streams and standing water in your kitchen can all harbor different types of bacteria. The type of bacteria in the water source will often depend on the amount of salt that is in the water. Bacteria in an aqueous solution have a preference for the amount of salt or other ions. An increase in salt outside the bacterial cell results in a change in pressure that could cause the bacteria to shrink, or crenate, to a dangerous size. Bacteria which can withstand a high amount of salt, halophiles, have a cell wall that is thick and can protect it from changes in the amount of salt around it.
References
- U.S. Department of Energy: Bacteria and Cheese
- "Microbiology: 6th Edition"; Lansing Prescott, John Harley and Donald Klein; 2005
