RT Journal Article SR Electronic T1 Probiotics: Growth-Promoting Factors Produced by Microorganisms JF Science JO Science FD American Association for the Advancement of Science SP 747 OP 748 DO 10.1126/science.147.3659.747 VO 147 IS 3659 A1 Lilly, Daniel M. A1 Stillwell, Rosalie H. YR 1965 UL http://science.sciencemag.org/content/147/3659/747.abstract AB Several species of protozoa, during their logarithmic phases of growth, produce substances that prolong the logarithmic phase in other species. The effect is not as striking as the inhibition of growth caused by antibiotics, but a consistent 50-percent increase in growth has been obtained with Tetrahymena pyriformis in response to a factor produced by Colpidium campylum.