Abstract
BackgroundMembers of the genus Planococcus have been revealed to utilize and degrade solvents such as aromatic hydrocarbons and alkanes, and likely to acquire tolerance to solvents. A yellow marine bacterium Planococcus maritimus strain iso-3 was isolated from an intertidal sediment that looked industrially polluted, from the Clyde estuary in the UK. This bacterium was found to produce a yellow acyclic carotenoid with a basic carbon 30 (C30) structure, which was determined to be methyl 5-glucosyl-5,6-dihydro-4,4′-diapolycopenoate. In the present study, we tried to isolate and identify genes involved in carotenoid biosynthesis from this marine bacterium, and to produce novel or rare C30-carotenoids with anti-oxidative activity in Escherichia coli by combinations of the isolated genes.ResultsA carotenoid biosynthesis gene cluster was found out through sequence analysis of the P. maritimus genomic DNA. This cluster consisted of seven carotenoid biosynthesis candidate genes (orf1–7). Then, we isolated the individual genes and analyzed the functions of these genes by expressing them in E. coli. The results indicated that orf2 and orf1 encoded 4,4′-diapophytoene synthase (CrtM) and 4,4′-diapophytoene desaturase (CrtNa), respectively. Furthermore, orf4 and orf5 were revealed to code for hydroxydiaponeurosporene desaturase (CrtNb) and glucosyltransferase (GT), respectively. By utilizing these carotenoid biosynthesis genes, we produced five intermediate C30-carotenoids. Their structural determination showed that two of them were novel compounds, 5-hydroxy-5,6-dihydro-4,4′-diaponeurosporene and 5-glucosyl-5,6-dihydro-4,4′-diapolycopene, and that one rare carotenoid 5-hydroxy-5,6-dihydro-4,4′-diapolycopene is included there. Moderate singlet oxygen-quenching activities were observed in the five C30-carotenoids including the two novel and one rare compounds.ConclusionsThe carotenoid biosynthesis genes from P. maritimus strain iso-3, were isolated and functionally identified. Furthermore, we were able to produce two novel and one rare C30-carotenoids in E. coli, followed by positive evaluations of their singlet oxygen-quenching activities.
Highlights
Carotenoids, essential pigments for photosynthesis, are known to protect cells from oxidative stress [1, 2]
The carotenogenic-bacterial species of the phylum Firmicutes of low GC Grampositive bacteria that have been reported to synthesize only C30-carotenoids include Streptococcus faecium [3], Staphylococcus aureus [4], Bacillus firmus [5], Halobacillus halophilus [6, 7], Planococcus maritimus [8, 9], Sporosarcina aquimarina [10], and Lactobacillus plantarum [11]. C30-Carotenoids have been found in bacterial species that belong to other phyla, such as Rubritalea squalenifaciens of the phylum Verrucomicrobia [12] and Methylomonas sp. strain 16a of the phylum Proteobacteria [13]
Isolation of the carotenoid biosynthesis gene cluster from P. maritimus strain iso‐3 A yellow colony including a 7.3-kb genomic insert from P. maritimus strain iso-3 was obtained by functional cloning experiments using Bacillus subtilis as the host
Summary
Carotenoids, essential pigments for photosynthesis, are known to protect cells from oxidative stress [1, 2]. Among the non-photosynthetic bacteria, several species have been shown to produce acyclic carotenoids with a Takemura et al Microb Cell Fact (2021) 20:194 basic carbon 30 (C30) structure instead of the typical C40-carotenoids. A yellow marine bacterium Planococcus maritimus strain iso-3 was isolated from an intertidal sediment that looked industrially polluted, from the Clyde estu‐ ary in the UK. This bacterium was found to produce a yellow acyclic carotenoid with a basic carbon 30 (C30) structure, which was determined to be methyl 5-glucosyl-5,6-dihydro-4,4′-diapolycopenoate. We tried to isolate and identify genes involved in carotenoid biosynthesis from this marine bacterium, and to produce novel or rare C30-carotenoids with anti-oxidative activity in Escherichia coli by combinations of the isolated genes
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