Minute tubular forms in soil.

Large numbers of minute, flat, long, straight, but often broken structures were observed in aqueous extracts of soil. We have applied the purely descriptive term 'tubules' to these structure, because they apparently became flattened during preparation for electron-microscopic viewing. The tubules appeared to be composed of parallel fibers held together by protein. Most of the tubules fell within a ranged of 10 to 50 nm in width. Lengths (of broken pieces) ranged from 0.2 to 1 micron or more. A few unbroken ends were found. They were rounded. Tubular structures of similar dimensions were found surrounding lysed cells in sectioned preparations of bacteria that had been separated from soil. The tubules were present in surface soils but not a subsurface sample. Their numbers decreased during bacterial multiplication in soil or broth containing soil. No evidence was found of cleared areas or increase in number of tubules when the tubules were plated with a heterogeneous microbial flora from soil.