Cyanobacterial cultures - absorption spectra, phycocyanin and phycoerythrin concentration for selected cultures

Brief description

The absorption spectra together with the phycocyanin and phycoerythrin concentrations were measured on ten cyanobacterial cultures obtained from the Australian National Algae Culture Collection (ANACC) based at CSIRO, Hobart, Tasmania, Australia.

Lineage

All cultures except CS-601, were maintained at 20°C on a 12/12 hour light/dark cycle. CS-601 was maintained at 6°C on 24 hour low light.
Absorption spectra for each culture were recorded from culture suspensions in 1 cm cuvettes positioned against an integrating sphere in a Cintra 404 UV/VIS dual beam spectrophotometer. The reference solution for each culture was the media solution used for that culture.
For phycocyanin and phycoerythrin concentrations; approximately 3 ml of each culture was filtered through a 25 mm glass fibre filter (Whatman GF/F) and the filter folded in half and stored in a cryovial in liquid nitrogen until analysis. Each culture filter was ground in a glass mortar and pestle with 5 ml of 0.1 M phosphate buffer (pH 6.5). The extract was transferred to a 10 ml centrifuge tube, vortexed for 20 seconds, sonicated in an ice water bath for 20 minutes before storing at 4°C in the for 3 hours. The culture extracts were then centrifuged for 5 minutes at 2500rpm (-2°C). The volume of the final extract was recorded before analysis using a Perkin Elmer LS50B Luminescence Spectrometer. Phycocyanin and phycoerythrin standards were prepared in the same way (storage at 4°C in the dark for 3 hours) on the day of analysis. The excitation and emission wavelengths for phycocyanin, and phycoerythrin, were 620/640 and 543/562 nm resepectively. Note that this method does not provide 100% extraction of PC and PE for all cultures. However the purpose of providing this data is to show which species/cultures contained PC, PE or both, rather than an accurate concentration.