Color me bad – microbial pigments as virulence factors
Colors are vital to the sensing of the environment and have evolved in higher living organisms to guide their interactions with others. For example, it is well appreciated that many birds exhibit brightly colored plumage to attract members of the opposite sex, that a chameleon’s adaptation to surrounding color is an important means of camouflage, and that the bright coloration of the poison dart frog warn potential predators to stay away. But such explanations cannot be offered to explain why certain microorganisms are pigmented. Because they lack color perception, one must assume evolutionary selective pressures behind the acquisition of pigments that promotes survival independent of their light absorbance, reflection or emission spectral properties.
A hallmark feature of several pathogenic microbes is the distinctive color of their colonies when propagated in the clinical laboratory. Such pigmentation comes in a variety of hues, and has often proven useful in presumptive clinical diagnosis. Recent advances in microbial pigment biochemistry and the genetic basis of pigment production have sometimes revealed a more sinister aspect to these curious materials that change the color of reflected light by selective light absorbance. In many cases, the microbial pigment contributes to disease pathogenesis by interfering with host immune clearance mechanisms or by exhibiting pro-inflammatory or cytotoxic properties. We review several examples of pigments that promote microbial virulence, including the golden staphyloxanthin of Staphylococcus aureus, the blue-green pyocyanin of Pseudomonas spp., and the dark brown or black melanin pigments of Cryptococcus neoformans and Aspergillus spp. Targeted pigment neutralisation might represent a viable concept to enhance treatment of certain difficult infectious disease conditions.
Color me bad: microbial pigments as virulence factors. Trends in Microbiology Aug 31 2009
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Tags: Bacteria, Biology, Medicine, Microbiology, Science, virulence
