HI,
I am trying to isolate marine bacteria using zobells marine broth 2216. Before inoculation the color of zobells marine broth 2216 was same as nutrient broth but on incubation after 3-5 days it was found to be black.
So i just want to know what factor is responsible for the black color of enriched zobells marine broth 2216.
Thank you.
I am no expert for this medium, but based on the composition there is nothing in it that would easily explain the color change. Might be iron sulfide, if a sulfate reducer is present, but that would precipitate.
So the most likely factor is a pigment produced by one of your bacteria. For example, some Streptomyces species produce Actinorhodin upon reaching stationary phase when the right nutrients are present.
Zobell marine broth 2216 contains ferric citrate and sodium sulfate. In the presence of sulfur reducing bacteria in the marine sediments, concurrent reduction of ferric and sulfate to ferrous sulfide.
http://aem.asm.org/content/43/2/319.full.pdf+html
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