Photometric and photo accoustic measurement of the absorbance of micro-organisms and its relation to the micro-organism-grain hypothesis

Absorption of E. Coli and other micro-organisms are measured by the standard optical spectroscopy and by the photo-acoustic method. The former method does not yield an extinction peak at λ = 220 nm but yields a weak one at λ = 270 nm, while by the latter method absorption peaks at λ = 220 nm and a weaker one at λ = 270 nm have been found for the spore of Bacillus subtilis. The well-known amino-acid, triptophan shows absorption peaks at λ = 220 and 280 nm. It is tentatively concluded that for the micro-organism model of interstellar grains to be viable, they may have to be spores rather than ordinary cells.