Diatoms on Earth, comets, Europa and in interstellar space

There exists a close correspondence between the measured infrared propertie s of diatoms and the infrared spectrum of interstellar dust as observed in the Trapezium nebula and toward the galactic center source GC-IRS 7. Diatom s and bacteria also exhibit an absorbance peak near 2200 Angstrom, which is found to agree with the observed ultraviolet absorbance properties of inte rstellar grains. We review the observational data and consider the known pr operties of diatoms and bacteria. It is suggested that these characteristic s are consistent with the concept of a cosmic microbiological system in whi ch these or similar microorganisms might exist on comets, Europa and in int erstellar space.