Staphyloxanthin
Encyclopedia
Staphyloxanthin is a carotenoid
pigment
that is produced by some strains of Staphylococcus aureus
. It acts as a virulence factor. It has an antioxidant
action that helps the microbe evade death by reactive oxygen species
produced by the host immune system. Staphyloxanthin is responsible for S. aureus' characteristic golden colour. When comparing a normal strain of S. aureus with a strain modified to lack staphyloxanthin, the wildtype pigmented strain was more likely to survive incubation with an oxidizing chemical such as hydrogen peroxide
than the mutant strain was. Colonies of the two strains were also exposed to human neutrophils
. The mutant colonies quickly succumbed while many of the pigmented colonies survived. Wounds on mice were inoculated with the two strains. The pigmented strains created lingering abscess
es. Wounds with the unpigmented strains healed quickly.
These tests suggest that the staphyloxanthin may be key to the ability of S. aureus to survive immune system attacks. Drugs designed to inhibit the bacterium's production of the staphyloxanthin may weaken it and renew its susceptibility to antibiotics. In fact, because of similarities in the pathways for biosynthesis of staphyloxanthin and human cholesterol
, a drug developed in the context of cholesterol-lowering therapy was shown to block S. aureus pigmentation and disease progression in a mouse infection model.
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
that is produced by some strains of Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
. It acts as a virulence factor. It has an antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
action that helps the microbe evade death by reactive oxygen species
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....
produced by the host immune system. Staphyloxanthin is responsible for S. aureus' characteristic golden colour. When comparing a normal strain of S. aureus with a strain modified to lack staphyloxanthin, the wildtype pigmented strain was more likely to survive incubation with an oxidizing chemical such as hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
than the mutant strain was. Colonies of the two strains were also exposed to human neutrophils
Neutrophil granulocyte
Neutrophil granulocytes are the most abundant type of white blood cells in mammals and form an essential part of the innate immune system. They are generally referred to as either neutrophils or polymorphonuclear neutrophils , and are subdivided into segmented neutrophils and banded neutrophils...
. The mutant colonies quickly succumbed while many of the pigmented colonies survived. Wounds on mice were inoculated with the two strains. The pigmented strains created lingering abscess
Abscess
An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...
es. Wounds with the unpigmented strains healed quickly.
These tests suggest that the staphyloxanthin may be key to the ability of S. aureus to survive immune system attacks. Drugs designed to inhibit the bacterium's production of the staphyloxanthin may weaken it and renew its susceptibility to antibiotics. In fact, because of similarities in the pathways for biosynthesis of staphyloxanthin and human cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
, a drug developed in the context of cholesterol-lowering therapy was shown to block S. aureus pigmentation and disease progression in a mouse infection model.