Thermoactinomyces is a genus of gram-positive endospore-forming bacteria. Members of the genus are present in soil and are commonly found in natural high-temperature habitats such as leaf and compost heaps and overheated stores of hay, grain, and other plant materials. Thermoactinomyces are thermophilic, they grow best at 55°-65° C. Only Actinomycetes and a few algae grow above 55° C. If the moisture content is in the range of 40-60 percent, other bacteria cannot compete effectively. With proper control and moisture, thermophilic actinomycetes will be predominant if not the only organism present in the growing media. All plants and plant wastes are potential substrates for these organisms.

Thermoactinomyces form heat-resistant true endospores on both their aerial and substrate mycelium. Spores produced by Thermoactinomyces have calcium dipicolinate (salt of calcium and pyridine-2,6-dicarboxylic acid [IUPAC], or dipicolinic acid) and have the typical structure of endospores. The endospores are formed within hyphae and have outer- and inner spore-coat, a cortex, and a central core. These spores are able to survive at 100° C for more than 20 min.

Spent mushroom compost
Thermoactinomyces vulgaris are the predominant members of the spent mushroom compost.

Thermoactinomyces have a remarkable longevity. Viable Thermoactinomyces spores were detected in sediments deposited about 7,000 to 7,500 years ago. Additional evidence comes from a report mentioning Thermoactinomyces spores which were found in debris from a Roman archeological in Northumberland UK., dated between A.D. 85 and 95.

Thermoactinomyces are alkaliphiles, or organisms that grow best at least two pH units above neutrality (7.0). Alkalithermophilic Thermoactinomyces strain HS682 produces extracellular serine protease enzyme within an average pH range of 10.3 (7.5-11.5). Thermoactinomyces sacchari strain A-1 and Thermomyces lanuginosus produce cellulase free extracellular endo-1,4-Β-xylanase enzyme (EC at pH 8.5.[5]

Thermoactinomyces vulgaris species has been implicated in causing hypersensitivity pneumonia, also called allergic alveolitis or "farmer's lung disease.It is also the cause of bassosis, or hypersensitivity pneumonitis caused by inhalation of Thermoactinomyces spores in moldy bagasse (sugar cane fibrous residue after the extraction of sugar juice).

Thermoactinomyces daqus H-18 is a new species of Thermoactinomyces isolated from high-temperature Daqu used in the fermentation of Bandongjing sesame-flavor liquor. Daqu, a primary microbial source and traditional fermentation starter, has been used to produce certain foods, such as vinegar and Chinese liquor with an attractive flavor for thousands of years (1,–3). The production of Bandongjing sesame-flavor liquor occurs through mixed-microbial fermentation, while the high-temperature Daqu provides the microorganisms in this process.5


  1. Microbial Processe, National Research Council (U.S.). Board on Science and Technology for International Development. Panel on Microbial Processes
  2. Microbiology By Daniel V. Lim
  3. Microbes: an invisible universe By Howard Gest
  4. Principles Of Microbiology:M&S By Mehrotra And Sumbali
    5. Alkalithermophiles by J. Wiegel and V.V. Kevbrin
  5. Genome Sequence of Thermoactinomyces daqus H-18, a Novel Thermophilic Species Isolated from High-Temperature Daqu (2015)



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