Carotenoid Biosynthesis inCalothrixsp. 336/3: Composition of Carotenoids on Full Medium, During Diazotrophic Growth and After Long-Term H₂Photoproduction

Abstract

The carotenoid composition of the filamentous heterocystous N-fixing cyanobacterium Calothrix sp. 336/3 was investigated under three conditions: in full medium (non-diazotrophic growth); in the absence of combined nitrogen (diazotrophic growth); and after long-term H photoproduction (diazotrophic medium and absence of nitrogen in the atmosphere). Anabaena sp. PCC 7120 and its ΔhupL mutant with disrupted uptake hydrogenase were used as reference strains. Analysis of identified carotenoids and enzymes involved in carotenogenesis showed the presence of three distinct biosynthetic pathways in Calothrix sp. 336/3. The first one is directed towards biosynthesis of myxoxanthophylls, such as myxol 2'-methylpentoside and 2-hydroxymyxol 2'-methylpentoside. The second pathway results in production of hydroxylated carotenoids, such as zeaxanthin, caloxanthin and nostoxanthin, and the last pathway is responsible for biosynthesis of echinenone and hydroxylated forms of ketocarotenoids, such as 3'-hydroxyechinenone and adonixanthin. We found that carotenogenesis in filamentous heterocystous cyanobacteria varies depending on the nitrogen status of the cultures, with significant accumulation of echinenone during diazotrophic growth at the expense of β-carotene. Under the severe N deficiency and high CO supply, which leads to efficient H photoproduction, cyanobacteria degrade echinenone and β-carotene, and accumulate glycosylated and hydroxylated carotenoids, such as myxol (or ketomyxol) 2'-methylpentosides, 3'-hydroxyechinenone and zeaxanthin. We suggest that the stability of the photosynthetic apparatus in Calothrix sp. 336/3 cells under N deficiency and high carbon conditions, which also appeared as the partial recovery of the pigment composition by the end of the long-term (∼1 month) H photoproduction process, might be mediated by a high content of hydroxycarotenoids.

Genomic Survey of Salt Acclimation-Related Genes in the Halophilic Cyanobacterium Euhalothece sp. Z-M001

“…The failure of several Euhalothece crtW/O candidate genes to produce keto-carotenoids in β-Car-accumulating E. coli is consistent with this genomic survey. Based on this information, we propose the carotenoid biosynthesis pathway present in Euhalothece 35,36 (Fig. 3C).…”

The use of cyanobacterial metabolites as natural medical and biotechnological tools: review article

“…They play an important role in photosynthesis through harvesting light between 400 and 500 nm and transferring energy to chlorophyll through a single-singlet energy transfer mechanism. Besides, their roles in photosynthesis, carotenoids have antioxidant activity making it strong photo-protectant molecules (Hirschberg & Chamovitz, 1994;Kosourov et al, 2016). B-carotene ( Figure 2) is used in protection from cardiovascular disorders (Zhang et al, 2014) and Dunaliella salina is a major biological source of b-carotene pigment, producing more than 14% of it as dry biomass (Spolaore et al, 2006).…”

Natural Products from Cyanobacteria: Focus on Beneficial Activities

“…Indeed, antioxidant activity has been characterized for the carotenoids, chlorophyll, the mycosporine-like amino acids (MAAs), and the phycobiliproteins such as phycocyanin (Table 10). [333,336]. Five carotenoids are found in the majority of cyanobacteria: β-carotene, zeaxanthin, nostoxanthin, echinenone, and canthaxanthin [332].…”

“…Five carotenoids are found in the majority of cyanobacteria: β-carotene, zeaxanthin, nostoxanthin, echinenone, and canthaxanthin [332]. In addition to their role in light harvesting, carotenoids act as potent photoprotectant molecules and show antioxidant activity through ROS scavenging [332,336] (Table 10). scavenging and, on the contrary, singlet oxygen production under high light conditions, mitigating their potential use as antioxidant therapeutics [332] (Table 10).…”