374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



be of a less common genus of a nonsporing nature, termed Actinomy- 

 ces. These aberrant, anaerobic plants have their own unique chem- 

 istry, structure, and life potential. Some of their representatives 

 were known to the medical profession as far back as 1860 as the 

 causal organisms of "lumpy jaw" in cattle and man. They are now 

 identified as agents of dangerous pulmonary abscesses and other in- 

 fections ("actinomycoses") which are very stubborn — often yielding 

 only to appropriate antibiotics derived from their kin^ the Streptomy- 

 cetes. 



An actinomycete of any description exists in the soil as a spider- 

 weblike entanglement of filaments of the diameter of bacteria (one 

 micron). Under a light microscope, these filaments are too narrow 

 to reveal their internal structure, as is true of bacteria generally. The 

 electron microscope becomes the instrument of choice in delineating 

 the finer parts of the protoplasm of all microorganisms, as it gives 

 a magnification up to 150 times that of light microscopes, with the dis- 

 advantage, however, of portraying only dead, dried specimens as 

 mounted in a high vacuum. The filaments thus treated portray 

 complicated, infolded membranes, granules of diverse sizes and com- 

 positions, and irregular islands of nucleoplasm. The continuous (non- 

 septate) tubular filaments branch profusely. The branches may im- 

 politely disregard one another or be more amicable and intertwine, 

 interlock, or even fuse. Filaments from two or more plants may 

 thus contain segments of a polyglot character, with opportunities for 

 a mixing of diverse genetical materials. 



The actinomycetes are usually classified as a filamentous order of 

 bacteria. Streptomyces is one of a half-dozen genera of actinomy- 

 cetes. It is characterized by the formation of spores in long chains, 

 at the end of special coarse, aerial filaments which protrude above the 

 substance on which the plant is growing. In nature the spores are 

 blown helter-skelter by the wind, to germinate into filaments if they 

 chance to fall on a moist, comfortably warm surface. They may, 

 however, remain dormant for months, protected as they are by a thick 

 waxy wall, derived from the filament within which they formed. The 

 walls have recently been observed under the electron microscope as 

 smooth or variously ornamented, for example, with spines like a mini- 

 ature cocklebur. The ornamentations prove to be a convenient crite- 

 rion for the delineation of species. 



The fine structure of the interior of the very small spores and 

 filaments is being studied at the University of Michigan by Dr. Pearl 

 Lui Chen, a botanist of the Albion College faculty. The spores are 

 killed and preserved by chemical treatment, with as little distortion 

 in structure as possible. They are then imbedded m a plastic, sec- 

 tioned on a machine into several serial slices per spore. These slices 

 are appropriately mounted on grids for observation under the electron 



