Microorganisms adapt to normal physiological environment to function optimally but any extreme change in environmental condition is capable of causing injury to the organism. The level or degree of environmental change will determine its effect on the organism. Many microorganisms only have the ability to tolerate little alteration in environmental condition within the limit of survival or antimicrobial resistance.
Certain microorganisms with the ability to tolerate extreme conditions are the Psychrophiles, acidophiles as well as halophiles. Psychrophiles can grow at a very low temperature of 00c with optimum growth at 150c and maximum growth at 200c. Acidophiles can tolerate extreme acidic conditions of between pH 1.0 to 5.5 while halophiles require a high level of salinity for optimum growth.
In general, microorganisms are designed to be adaptable. This is usually as a result of the composition of their surrounding wall and inbuilt genetic material. Alterations to extreme conditions can either be reversible or irreversible. Reversible alteration results in the disappearance of stress when the particular pressure is lifted whereas irreversible alteration causes the change to be permanent thereby resulting into passing on the changes to subsequent generation of microorganisms.
One of the ways by which microorganisms adapt to extreme environmental conditions is resistance. Microorganisms tend to develop resistance to antibiotics whenever it is introduced. For instance, resistance to the first antibiotic (penicillin) discovered in 1929 was recognized almost instantly after the introduction of the drug. The adaptation of microorganisms to any agent can occur in two different ways. The first method of adaptation is referred to as natural or inherent resistance mechanism while the second means of adaptation is acquired resistance.
Some microorganisms (Gram negative organisms) have a special surrounding membrane that prevents the penetration of certain agents making it difficult for the agent to hit its intracellular target. This is an example of a natural resistance built by a microorganism. Acquired resistance is as a result of alteration in the genetic makeup of the microorganism. The later method of resistance can occur from mutation or the pressure exerted by the stress-agent. This genetic change can then be passed on to succeeding generation.
Microorganisms can adapt to any extreme environmental condition including temperature, pH, chemicals and ion concentrations. Another adaptation mechanism make use of the strategy of sensing of the presence of a chemical composition in the environment and the subsequent migration towards the chemical compound or change of direction away from the chemical if it is sensed by the organism to be toxic. The method of adaptation involved in chemotaxis must have a memory that will process a given level of concentration of a compound each and every time a microorganism is exposed for similar kinetic response.
In conclusion, the adaptation of microorganisms to extreme environmental condition is a complex alteration that enables the organism to still perform its normal metabolic function and survive. Such adaptation may either be through natural or acquired mechanism. Natural adaptation is inbuilt and essentially involves the inherent nature of microorganism’s membrane to withstand changes in the environment. Acquired adaptation is through permanent change in the genome of a microorganism which may be passed to the next generation. A special type of adaptation involving the directional movement of microorganism, towards or away from a chemical compound, is chemotaxis.
Bibliography
Beales, N. ‘Adaptation of microorganisms to cold temperatures, weak acid preservatives, low pH, and osmotic stress: A review.’ Comprehensive reviews in food science and food safety 3(2004): 1.
Walsh Christopher. ‘Antibiotics: Actions, origins, resistance’. Washington DC: American Society for Microbiology Press, 2003.