CLASS III. MICROTATOBIOTES PHILIP, 1956.* 

 (Canad. Jour. MicrobioL, 2, 1956, 261.) 



Mic.ro.ta.to.bi.o'tes. Gr. sup. adj. microtatus smallest; Gr. noun biote life; M.L. 

 fern. pi. n. Microtatohiotes smallest living things. 



Includes the smallest of the living things. All are manifested by a dependence on other 

 living organisms for their growth and multiplication. Parasitism is axiomatic since there is 

 no way to determine if there are free-living forms. Most of these organisms occur intracel- 

 lularly; Rickettsia quintana Schmincke of trench fever is an example of extracellular growth 

 in its host, the body louse. A few of the visible forms are known to occur intranuclearly. 

 Characteristic, intracellular inclusion bodies are often associated with the smaller agents. 

 Hosts are represented from the highest members of the plant and animal kingdoms to the 

 lowliest of microbial life. Some species utilize both intermediate and definitive hosts for 

 their propagation. The largest members are the rickettsia-like organisms which are often 

 pleomorphic, including coccoid to filamentous forms, while others show morula-like clusters 

 of elementary bodies occurring as one or up to twenty colonies in an infected cell. Some 

 species show larger ellipsoidal granules with a fairlj^ compact matrix of as much as 2 microns 

 in diameter termed initial bodies from which, in most instances, the groups of smaller ele- 

 mentary bodies are believed to be derived though no life cycle is postulated (Coles, Ann. 

 N. Y. Acad. Sci., 56, 1953, 458). At least three of these larger species, visible under the light 

 microscope, have phases which pass through coarse or medium filters, e.g., Coxiella burnetii 

 Philip of Q fever. 



The small members grade downward to filterable virus particles susceptible of measure- 

 ment only by physico-chemical techniques and by special preparation under the electron 

 microscope. Special staining procedures are required for forms visible under the light 

 microscope and for studjdng characteristic pathologic reactions or associated inclusion 

 bodies in the tissues of affected hosts. Special tissue-culture techniques have been developed 

 for the more adequate investigation of many of the species. 



Two orders are included in Class Microtatobiotes. 



Key to the orders of class Microtatobiotes. 



I. Individual organisms are not ultramicroscopic except perhaps in rare filterable phases 

 and are usually more than 0.1 micron in diameter. Parasites of members of the animal 

 kingdom. 



Order I. Rickettsiales , p. 934. 

 II. Individual organisms are usually ultramicroscopic and filterable. Except for a few pox 

 viruses of animals and a few plant viruses, the virus particles are less than 0.1 micron 

 in diameter. Parasites of both the plant and animal kingdoms. 



Order II. Virales, p. 985. 



* Prepared and edited by Dr. Cornelius B. Philip, U. S. Public Health Service, Rocky 

 Mountain Laboratory, Hamilton, Montana. 



933 



