Bacteria are among the most diverse organisms on the planet. They are found in the widest range of habitats and vary extremely as to their physiological tolerance. Therefore, the bacteria requirements needed for them to live differ from species to species, although there are a few common requirements.
Bacteria were among the first life forms. However, people were unaware these small organisms existed until the late 1600s when Antonie van Leeuwenhoek viewed bacterial cells for the first time under a primitive microscope. Over the next few hundred years, microscopes became more and more sophisticated and the field of bacteriology has blossomed.
Bacteria are found in a wider variety of habitats than any other organism on earth. Each species of bacteria has environments in which it thrives. For example, thermophiles live in high temperatures, whereas acidphiles live in acidic conditions. Where bacteria live often determine their requirements for life.
Most bacteria grow best a pH levels around neutral, aka 7. However, bacterial pH requirements can range from very acidic (4 or less) to more alkaline conditions (~10 and up).
In order to live, bacteria need a source of food and a place to live that is within their physiological tolerance. Bacteria vary from species to species with respect to food bacteria requirements, but almost all require nutrition of some sort from an external source.
Food sources widely used by humans are especially vulnerable to bacterial growth because they are particularly nutritious. Some bacteria species do not require food per se, but can produce their own nutrition much as a plant does through photosynthesis. These bacterial species are less common, however. Bacteria also need moisture in order to thrive. Bacteria do not live long on hard, cold surfaces with no moisture, and food that is freeze-dried cannot support bacteria.
The physiological tolerances of bacteria also vary from species to species. Some species can thrive in very saline conditions, while others will die immediately. Others thrive under oxygen-free condition, whereas some will die without oxygen present.
FATTOM: An Easy Way to Remember Bacteria Requirements
FATTOM is an acronym often used in the food industry as a way to remember conditions that lead to food spoilage, aka bacterial growth. FATTOM stands for Food Acidity Time Temperature Oxygen Moisture.
Like all organisms on earth, bacteria require water to survive. That's where moisture comes in. Any moisture in food or in the environment will allow bacteria to thrive. That's why dried foods like dry beans, rice and jerky last much longer than fresh or cooked foods.
Oxygen is also needed by almost all bacteria (there are some bacterial species that are anaerobic aka bacteria that live in environments lacking oxygen). That's why sealing food in cans or bottles without oxygen allows them to last much longer since it prevents bacterial growth.
Acidity, aka pH level, does depend on the type of bacteria you're talking about. However, most bacteria don't survive well in acidic pHs of less than 4.5, which is why foods pickled in acidic substances like vinegar or lemon juice often last longer since bacteria cannot usually grow in those conditions.
There are many species of bacteria that benefit humans. Certain bacterial species are responsible for fermentation and the creation of foods such as pickles and sauerkraut. Other bacteria have the ability to digest contaminants, and can serve to clean up environmental spills. There are also millions of bacteria inhabiting the human digestive system, from the mouth to the large intestine, which help to digest food and produce vitamins vital to life.
Some species of bacteria are pathogenic, which means they have the potential to cause disease. Diseases such as syphilis, cholera, the bubonic plague and tetanus are all caused by bacteria. Fortunately, many of these disease-causing bacteria are easily killed with antibiotics; however, there are some species that are becoming resistant to treatment with traditional antibiotics.