Actinobifida chromogena Microbispora bispora Micropolyspora faeni Nocardia sp.
Pseudocardia thermophilia Streptomyces rectus S. thermofuscus S. thermoviolaceus S. thermovulgaris S. violaceus-ruber Thermoactinomyces sac chari
Thermomonospora curvata T. viridis
Aspergillus fumigatus Humicola grisea H. insolens H. lanuginosa Malbranchea pulchella Myriococcum themophilum Paecilomyces variotti Papulaspora thermophila Scytalidium thermophilim Sporotrichum thermophile
Source: Palmisano, Anna C. and Barlaz, Morton A. (Eds.) (1996). Microbiology of Solid Waste. Pp. 125-127. CRC Press, Inc., 2000 Corporate Blvd., N.W., Boca Raton, FL 33431 USA.
Alcaligenes faecalis Bacillus brevis B. circulans complex B. coagulans type A B. coagulans type B B. licheniformis B. megaterium B. pumilus B. sphaericus B. stearothermophilus B. subtilis
Clostridium thermocellum Escherichia coli Flavobacterium sp. Pseudomonas sp. Serratia sp. Thermus sp.
bread to 740C (1650F). Heat from bacteria also warms germinating seeds, as seeds in a sterile environment are found to remain cool while germinating.24
Both mesophilic and thermophilic microorganisms are found widely distributed in nature and are commonly resident on food material, garbage and manures. This is not surprising for mesophiles because the temperatures they find to be optimum for their reproduction are commonly found in nature. These temperatures include those of warm-blooded animals, which excrete mesophiles in their stools in huge numbers.
A mystery presents itself, on the other hand, when we consider thermophilic microorganisms, since they prefer living at temperatures not commonly found in nature, such as hot springs, water heaters and compost piles. Their preference for hot temperatures has given rise to some speculation about their evolution. One theory suggests that the thermophiles were among the first living things on this planet, developing and evolving during the primordial birthing of the Earth when surface temperatures were quite hot. They have thus been called the "Universal Ancestor." Estimated at 3.6 billion years old, they are said to be so abundant as to "comprise as much as half of all living things on the planet." 25 This is a rather profound concept, as it would mean that thermophilic organisms are perhaps more ancient than any other living thing. Their age would make dinosaurs look like new-born babes still wet behind the ears, however extinct. Of course, we humans, in comparison, have just shown up on Earth. Thermophiles could therefore be the common ancestral organism of all life forms on our planet.
Just as extraordinary is the concept that thermophiles, despite their need for a hot environment, are found everywhere. They're lingering in your garbage and in your stool and have been since we humans first began to crawl on this planet. They have quietly waited since the beginning of time, and we haven't been aware of them until recently. Researchers insist that thermophiles do not grow at ambient or room temperatures.26 Yet, like a miracle, when we collect our organic refuse in a tidy pile, the thermophiles seem to be sparked out of their dormant slumber to work furiously toward creating the primordial heat they so desire. And they succeed — if we help them by creating compost piles. They reward us for our help by converting our garbage and other organic discards into life-sustaining earth.
The knowledge of living creatures incomprehensibly ancient, so small as to be entirely invisible, thriving at temperatures hotter than those normally found in nature, and yet found alive everywhere, is remarkable enough. The fact that they are so willing to work for our benefit, however, is rather humbling.
By some estimates, humanure contains up to a trillion (1,000,000,000,000) bacteria per gram.27 These are, of course, mixed species, and not by any means all thermophiles. A trillion bacteria is equivalent to the entire human population of the Earth multiplied by 166, and all squeezed into a gram of organic material. These microbiological concepts of size and number are difficult for us humans to grasp. Ten people crammed into an elevator we can understand. A trillion living organisms in a teaspoonful of crap is a bit mind-boggling.
Has anyone identified the species of microorganism that heats up compost? Actually, a large variety of species, a biodiversity, is critical to the success of compost. However, the thermophilic stage of the process is dominated by thermophilic bacteria. One examination of compost microorganisms at two compost plants showed that most of the bacteria (87%) were of the genus Bacillus, which are bacteria that form spores,28 while another researcher found that above 650C, the organisms in the compost were almost purely Bacillus stearother-mophilus.29
Was this article helpful?