Serratia marcescens can tolerate and grow at both temperature mentioned above but why there is a variation in pigment while temperature varies? What is the mechanism behind this?
Many literature state that colorful bacteria generally are cold tolerants or loving ones rather than mesophiles or thermophiles. Why so?
Prodigiosin production is temperature dependent
https://www.jstage.jst.go.jp/article/jsme2/19/3/19_3_236/_article
Prodigiosin production is temperature dependent
https://www.jstage.jst.go.jp/article/jsme2/19/3/19_3_236/_article
Definitely more research is necessary before a satisfying answer will be found.
It is currently thought that the pigment produced by Serratia, called prodigiosin, does not have any direct function, but rather is simply a byproduct of other processes. The relationship between cell density and pigment production has led some scientists to propose that this pigment is a secondary metabolite associated with "quorum sensing" gene expression patterns. Quorum sensing is a means by which bacterial cells communicate. Each cell releases signaling molecules into the environment, which other cells of the same species can detect. As the density of the population increases, so does the abundance of the signaling molecules. These signaling molecules in turn regulate gene expression in such a way that when a certain abundance of signaling molecules (and thus cells) exists, the cells alter their gene expression to change their metabolic strategy accordingly. This allows bacterial populations to maximize their efficiency in dealing with a rapidly changing environment, potentially even cooperatively coordinating their metabolic processes. In this model, as the Serratia, population size increases, their gene expression pattern changes accordingly. One of the consequences of this is that some new metabolic pathways are initiated, a byproduct of which is the prodigiosin pigment.
Serratia is found both in the environment and in the digestive tract of animals/insects. The red pigment, prodigiosin, which has many antimicrobial and cytotoxic properaties, would therefore be produced when the organism is in the soil etc. where it may be needed to fight off certain competing organisms. However, it may not be necessary to inhibit those organisms that would also be present inside the GI tract of animals and so is not produced. This would be an interesting question to investigate if it hasn't been done already (I wasn't able to find anything).
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