|MadSci Network: Microbiology|
As you may know from your studies, all life has the same BASIC NUTRITIONAL REQUIREMENTS which include:
A SOURCE OF ENERGY. This may be light (the sun or lamps) or inorganic substances like sulfur, carbon monoxide or ammonia, or preformed organic matter like sugar, protein, fats etc. Without energy life can not exist and quickly dies or becomes inactive.
A SOURCE OF NITROGEN. This may be nitrogen gas, ammonia, nitrate/nitrite, or a nitrogenous organic compound like protein or nucleic acid.
A SOURCE OF CARBON. This can be carbon dioxide or monoxide, methane, carbon monoxide, or complex organic material.
A SOURCE OF OXYGEN. All cells use oxygen in a bound form and many require gaseous oxygen (air), but oxygen is lethal to many microbes.
A SOURCE OF PHOSPHOROUS, SULFUR, MAGNESIUM, POTASSIUM & SODIUM.
A SOURCE OF CALCIUM. Most cells require calcium in significant quantities, but some seem to only need it in trace amounts.
A SOURCE OF WATER. All life requires liquid water in order to grow and reproduce; which is why the Mars Mission is so interested in water on Mars. Some resting stages of cells, like bacterial spores, can exist for long periods without free water, but they do not grow or metabolize.
A SOURCE OF MINERALS LIKE IRON, ZINC, COBALT, ETC. These are called TRACE metals that are required by some enzymes to function.
The sources of these various requirements defines an organism, so a description of every organism should include this information. Many bacteria can synthesize every complex molecule they need from the basic minerals, but others, said to be FASTIDIOUS, require PREFORMED organic molecules like vitamins, amino acids, nucleic acids, carbohydrates; humans are fastidious. In general bacterial pathogens need more PREFORMED ORGANIC MOLECULES than do nonpathogens, but that is not always true. For example some bacteria that are found in milk hardly make any of their own basic organic molecules, that is they let the cow (or more to the point the microbes that live in the cow's gut) make these things for them. A simple rule of thumb is "if humans can use something for food, many microbes will also love it". The reverse is not always as true as microbes can "digest" some very strange substances including cellulose, sulfur, some plastics, turkey feathers and oil, to name just a few.
In the case of your example, the source of energy and most of the carbon necessary for the growth of bacteria such as E. coli is coming primarily from the glucose and to a lesser extent the meat extract. The nitrogen, sulfur, magnesium, sodium, calcium, trace minerals, and some of the potassium are supplied by the meat extract. The potassium phosphate supplies both potassium and phosphate. The distilled water is obviously the main source of essential water. Finally, the oxygen is supplied mainly by the environment and to a lesser extent the distilled water.
Murray, P., E.J. Barron, J.H. Jorgensen, M.A. Pfaller, and R.H. Yolken. 2003. Manual of Clinical Microbiology, 8th Edition.
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