Biosynthesis of a novel C30 carotenoid in Bacillus firmus isolates.

AIMS: Pigmented Bacillus spp. with probiotic properties have been isolated. In the yellow-/orange-coloured strains, the carotenoid pigments present have been characterized. In contrast, the carotenoids 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 Bacillus firmus strains. METHODS AND RESULTS: A combination of UV/Vis, chromatographic and mass spectrometry (MS) has revealed the properties of 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 persists 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, which 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 that 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. CONCLUSION: 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. SIGNIFICANCE AND IMPACT OF THE STUDY: It could be shown that the C30 4,4'-diapolycopene-dioate derivatives protect pigmented B. firmus from peroxidative reactions. Under oxidative conditions, this can be an ecological advantage over nonpigmented (=noncarotenogenic) strains that are equally abundant.

Carotenoids found in Bacillus.

AIMS: To identify the diversity of pigmented aerobic spore formers found in the environment and to characterize the chemical nature of this pigmentation. MATERIALS AND RESULTS: Sampling of heat-resistant bacterial counts from soil, sea water and the human gastrointestinal tract. Phylogenetic profiling using analysis of 16S rRNA sequences to define species. Pigment profiling using high-performance liquid chromatography-photo diode array analysis. CONCLUSIONS: The most commonly found pigments were yellow, orange and pink. Isolates were nearly always members of the Bacillus genus and in most cases were related with known species such as Bacillus marisflavi, Bacillus indicus, Bacillus firmus, Bacillus altitudinis and Bacillus safensis. Three types of carotenoids were found with absorption maxima at 455, 467 and 492 nm, corresponding to the visible colours yellow, orange and pink, respectively. Although the presence of other carotenoids cannot be ruled out, these three predominant carotenoids appear to account for the pigments obtained in most pigmented bacilli, and our analysis reveals the existence of a C30 biosynthetic pathway. Interestingly, we report the presence of a water-soluble pigment that may also be a carotenoid. The function of carotenoids is photoprotection, and carotenoid-containing spores exhibited significantly higher levels of resistance to UV radiation than non-carotenoid-containing Bacillus species. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates that pigmented bacilli are ubiquitous and contain new carotenoid biosynthetic pathways that may have industrial importance.