Biosynthesis of a novel C30 carotenoid in Bacillus firmus isolates

Abstract Aims

Pigmented Bacillus spp. with probiotic properties have been isolated. In the yellow/orange coloured strains the carotenoid pigments present have been characterised. In contrast the carotenoid present in the Bacillus isolates coloured red await identification. The present article reports progress on the elucidation of the pigment biosynthetic pathway in these red pigmented Bacilllus firmus strains.

A combination of UV/Vis, chromatographic and mass spectrometry (MS) have revealed the properties the predominant pigment and the end‐point carotenoid of the pathway to be methyl 4, 4’ diapolycopene‐dioate after transmethylation. The diglycosyl ester of 4,4’‐diapolycopene‐dioate persisting in vivo prior to chemical treatment. Different mutants and inhibitor treatment were employed to establish the C30 biosynthesis pathway with all precursors and intermediates to 4,4’‐diapolycopene‐dioate detected. They include 4,4’‐diapophytene, and all desaturation intermediates to 4,4’‐diapolycopene and 4,4’‐diapolycopene‐dialdehyde. To cultures synthesizing the 4,4’‐diapolycopene‐dioate derivative and those in which its formation was inhibited, oxidative stress was induced by peroxide treatment. Conditions which decreased the growth rate of the pigmented cells by only 30% caused a complete growth inhibition of the culture devoid of the 4,4’‐diapolycopene‐dioate derivative.

This finding demonstrates the diversity of C30 carotenoid biosynthesis in Bacillus species and the antioxidative function of the 4,4’‐diapolycopene‐dioate derivative in B. firmus cells.

It could be shown that the C30 4,4’‐diapolycopene dioate drivatives protect pigmented B. firmus from peroxidative reations. Under oxidative conditions, this can be an ecological advantage over non‐pigmented (= non‐carotenogenic) strains which are equally abundant.

© 2012The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology