This is the first article in a series on viroids. Viruses, bacteria, and fungi; most people will have heard of these three major types of disease-causing microbes. Some will also have heard about ...

Biological entities called obelisks have been hiding—in large numbers—inside the human mouth and gut. These microscopic entities, which were recently discovered by a team at Stanford University, are ...

Proceedings of the National Academy of Sciences of the United States of America, Vol. 82, No. 14 (Jul. 15, 1985), pp. 4582-4586 (5 pages) On the basis of sequence homology a model is proposed for five ...