1. NUTRIENT AVAILABILITY: the accessibility of a necessary resource, substance or compound providing nourishment to maintain life, i.e. capable of conversion to energy and structural building blocks
- Fastidious: having complex nutritional or cultural requirements that make isolation and culture more difficult
- MAJOR ESSENTIAL ELEMENTS:
- C, O, H, N, S, P, K, Mg, Ca, Fe, Na, Cl
- MINOR ESSENTIAL ELEMENTS:
- Zn, Mn, Mo, Se, Co, Cu, Ni, W
2. PHYSICO/ENVIRONMENTAL PARAMETERS:
- WATER ACTIVITY/OSMOTIC PRESSURE:
- Water activity (aw): represents the available water
- Osmotic pressure (p): expressed in atmospheres; reflects the concentration of solute in an aqueous solution
- OXYGEN: pathogenic microorganisms may have metabolic oxygen requirements that are OBLIGATE or FACULTATIVE, ANAEROBIC or AEROBIC, or somewhere in between, MICROAEROPHILIC
- pH: "power of hydrogen"; a measurement of the amount of hydrogen ion in solution; the logarithm of the reciprocal of the hydrogen ion concentration in an aqueous solution used to express its acidity or alkalinity (0-14)
- TEMPERATURE:
- Psycrophile(psychrophilic): liking cold temperatures; optimal growth at 15o to 20oC
- Mesophile (mesophilic): liking moderate temperatures; optimal growth at 20o to 45oC
- Thermophile (thermophilic): liking elevated temperatures; optimal growth at 50o to 70oC
3. COMPETITION: the simultaneous demand by two or more organisms or species for a necessary, common resource or physical space that is in limited or potentially limited supply, resulting in a struggle for survival
- Niche: the place of an organism within its community or ecosystem
4. HOST IMMUNE SYSTEM: the cells and tissues involved in recognizing and attacking foreign substances in the body
Designed & Maintained by David M. Rollins
Copyright © 2000, D.M. Rollins and S.W. Joseph
Revised: September 2003
URL: http://life.umd.edu
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