I am isolating bacteria degrading lignin on agar plate. I found one bacteria turn the lignin plate into dark quickly while the bacteria do not turn TSA or LB plate into dark. What is the mechanism for turning lignin into dark? That plate is made of lignin and some salts (Bushnell-Hass medium). What do you think is an indicator of good lignin-degrading bacteria?
Just a query, if the bacteria was spread all over the plate or streaked ? Or bacteria was put into holes. I mean, did the bacteria come in contact with whole of the lignin-plate and the entire plate turned black ? Lignin must be brown, and further browning (dark) means oxidation of phenolic moieties in lignin making them brown- thus the bacteria must have "oxidase" activity. Alternatively, the lignin was degraded by bacteria (with "ligninase" activity) thus breaking the ligning into monomeric monolignols/phenolics which are autoxidised in presence of "air" only. To check the later event, the same bacteria if fed with only simple phenolics (sinpic acid etc.) must not yield darkening thus indicating absence of oxidase activity and only ligninase activity. Another very distant possibility would be that the bactrial cells are lysed (in contact with lignin) to release some chromophores which are bacterial pigments, or simply bacterial pigments oxidizing to dark ones. I would be interested to know the outcome of further results too. Best wishes.
The bacteria was streaked on lignin plate. I don't think the darkness is due to bacterial pigment produced since bacteria colony looks white and do not produce any pigment on LB and TSA plates.
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