Ultraviolet fluorescence excitation and emission spectroscopy of marine algae and bacteria

Ultraviolet (UV) excitation and emission spectra of cultures of marine bacteria and phytoplankton were investigated. The intensity of the emission band at 340 nm wavelength (λex=230 nm) is compared with cell number and protein content, and specific efficiencies are derived. Another weak emission band at 305 nm is found with most phytoplankton species. The same fluorescence signatures are observed with protein fragments and proteins of known composition and are caused by their tryptophan and tyrosine content. The UV fluorescence of marine particles is related to these aromatic amino acids bound to proteins.