Abstract
Objective: The aim of the present study was to express in Mycobacterium smegmatis the clustered mycobacterial genes coding for lycopene synthesis and to investigate the protective properties of lycopene against ultraviolet (UV) irradiation.Methods: The genes, which encode the biogenesis of lycopene in Mycobacterium aurum A+, were introduced into Mycobacterium smegmatis by electroporation. The pigments produced were analyzed by thin layer chromatography, and the absorption spectra were determined. A survival test using UV irradiations was also performed.Results: The transformed Mycobacterium smegmatis were found to synthesize lycopene with important yield (1.41± 3.09 mg/g) and was more resistant to ultraviolet irradiation than non-pigmented strain (p<0.01). Furthermore, cells of M. smegmatis not transformed but coated with lycopene are more resistant to UV than those uncoated (p<0.01).Conclusion: M. smegmatis can form orange colonies on agar plates when it is transformed with the lycopene genes, and the transformants produces 1.41 mg/g (dry weight) of this carotene. Our findings strongly suggest that lycopene has antioxidant activities and prevent the lethal action of UV irradiation on bacterial cells in vivo and in vitro, and deserves further studies considering the amelioration of the production.
Highlights
Carotenoids are a big family of fat-soluble pigments largely distributed in nature, in anoxygenic and oxygenic photosynthetic bacteria, algae and in many fungi, but animals and human are not able to produce this kind of pigments themselves [1, 2]
M. smegmatis was transformed with the pC51, vector constituted of the pHLD69 plasmid, and an insert of 4.42 kb containing genes necessary for lycopene biosynthesis [22]
Analysis of carotenoids Pigments produced by M. smegmatis harboring pC51 plasmid were extracted, purified and analyzed by Thin-layer chromatography (TLC)
Summary
Carotenoids are a big family of fat-soluble pigments largely distributed in nature, in anoxygenic and oxygenic photosynthetic bacteria, algae and in many fungi, but animals and human are not able to produce this kind of pigments themselves [1, 2]. Carotenoids are a class of hydrocarbon compounds that can be chemically subdivided into xanthophylls (oxygenated molecules) and carotenes (hydrocarbons lacking oxygen). These tetraterpenes usually consist of 8 isoprene units derived from isopentenyl diphosphate [3]. Carotenoids are produced through two different stages, the early steps and the later steps. The early steps include the formation of geranylgeranyl pyrophosphate (GGPP) from farnesyl pyrophosphate (FPP) by GGPP synthase (an enzyme encoded by the crtE gene). The formation of phytoene from GGPP is catalyzed by phytoene synthase (an enzyme encoded by the crtB gene). The phytoene obtained is dehydrated by a phytoene dehydrogenase (an enzyme encoded by the crtI gene) by converting phytoene into lycopene via the following intermediate molecules: phytofluene, zeta-carotene and neurosporene [4,5,6]
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