Why do these strands fluoresce differently?

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pwnell
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Joined: Fri Dec 18, 2009 4:59 pm
Location: Tsawwassen, Canada

Why do these strands fluoresce differently?

Post by pwnell »

It seems to my uninformed eye both kinds of strands are cyanobacteria, yet the green one fluoresces red (indicating to me that it most likely contains chlorophyll) - however the other two strands fluoresce green, suggesting they do not contain chlorophyll. In that case, how do they survive? These are all from my reef aquarium (hence salt water)

Image
40x, DIC

Image
40x, Fluorescence, UV/Blue excitation

Gyrosigma
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Joined: Fri Aug 04, 2006 6:39 am
Location: France Normandie
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Post by Gyrosigma »

Red : Chlorophyl... green ? I don't know....

Regards

Dominique

René
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Joined: Sun Oct 08, 2006 4:22 am

Post by René »

Hi Waldo,

Blue-greens have so-called antennae-pigments, which shift excitation and emission spectra away fom the chlorophyll a peaks. One of the major such carotenes is phycoerythrin, which fluorescesces green-yellow at around 570 nm.

That said, I'm not altogether sure that your species actuall is autotrophic, as it seems quite colourless in brightfield. With a band-pass emission filter for cholorophyll at around 670nm you can block the green/yellow, and see if it actually contains chlorophyll at all.


Best wishes, René

BJ
Posts: 354
Joined: Sat Sep 29, 2007 10:53 am
Location: England

Post by BJ »

Hi Waldo,


One filament has a pigmentation dominated by chlorophyll which fluoresces red. The other cyanobacterium has a pigmentation dominated by the strongly fluorescent protein "phycoerythrin". This filament will also have chlorophyll. I guess they are either different species or two filaments which have grown in different environments. Cells have more phycoerythrin in higher nutrient conditions (especially high nitrogen).

Such a diverse offering of photos from you.

Thank you once again!

Brian

pwnell
Posts: 2029
Joined: Fri Dec 18, 2009 4:59 pm
Location: Tsawwassen, Canada

Post by pwnell »

Thanks for the explanations. I unfortunately do not have a bandpass filter around 670nm so I cannot check on that...

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