Temperature and Microbial Activity

Microbes appear to have adapted to all temperatures at which there is liquid water, from the frigid waters around the Antartic to building hot springs. However, while each of these environments harbors one or more species of microbes, no known species thrives in all these condition. All microbes that have been studied, like the plants and animals discussed in this section, perform best over a fairly narrow range of temperatures. Let’s look at two microbes that libe in environments at opposite, extremes of the aquatic temperature spectrum. (Moles, 2005)

The organisms that live in the deep oceans live in darkness. Their environment is also cold, generally below 5ºC. This cold water environment extends to the surface in the Arctic and Antartic. A wide variety of organisms live in these cold waters.

Richard Morita (1975) studied the effect of temperature on population growth among cold-loving or psychrophilic, marine bacteria that live in waters around Antartica. He isolated and cultured one of those bacteria, Vibrio sp., in a temperature-gradient incubator for 80 hours. During the experiment, the temperature gradient within the incubator ranged from about -2ºC to  just over 9ºC. The results of the experiment show that this Vibrio sp. Grows fastest at about 4ºC. At temperatures above and below this, its population growth rate decreases. Morita recorded some growth in the Vibrio population at temperatures approaching -2ºC; however populations did not grow at temperatures above 9ºC. Morita has recorded population growth among some cold-loving bacteria at temperatures as low as -5,5ºC.

Some microbes can live at very high temperatures. Microbes have been found living in all of the hot springs that have been studied. Some of these heat living, or thermophilic, microbes grow at temperatures above 40ºC in a variety of environments. The most heat-loving microbes are the hyperthermophiles, which have temperature optima above 80ºC. Some hyperthermophiles grow best at 110ºC. Some of the most intensive studies of thermophilic and hyperthermophilic microbes have been carried out in Yellowstone National Park by Thomas Brock (1978) and his students and colleagues. One of the genera they have studied is Sulfolobus, a member of the microbial Domain Archaha, which obtains energy by oxidizing elemental sulfur. Jerry Mosser and colleagues (1974) used the rate at which Sulfolobus oxidizes sulfur as an index of its metabolic activity. They studied the microbes from a series of hot springs in Yellowstone National Park that ranged in temperature from 63ºC to 92 ºC. The temperature optimum for the Sulfolobus populations ranged from 63ºC to 80ºC and was related to the temperature of the particular spring from which the microbes came. For instance, one strain isolated from a 59ºC spring oxidized sulfur at a maximum rate at 63 ºC. This Sulfolobus population oxidizes sulfur at a hich rate within a temperature range of about 10ºC. Outside of this temperature range, its rate of sulfur oxidation is much lower.

We have reviewed how temperature can affect microbial activity, plant photosynthesis, and animal performance. These examples demonstrate taht most organisms perform best over a fairly narrow range of temperatures. Consider the effects of temperature on the performance of organisms relative to our discussion of how temperatures can vary gratly over small distances. Temporal variation in temperature can also be substantial. (Moles, 2005)


Reference:


Moles, M.CV. 2005. Ecology: Concept and Application. McGraw-Hill Inc., New York.