Effects of Light and Oxygen on Chlorophyll d Biosynthesis in a Marine Cyanobacterium Acaryochloris marina

Abstract

A marine cyanobacterium Acaryochloris marina synthesizes chlorophyll (Chl) d as a major Chl. Chl d has a formyl group at its C3 position instead of a vinyl group in Chl a. This modification allows Chl d to absorb far-red light addition to visible light, yet the enzyme catalyzing the formation of the C3-formyl group has not been identified. In this study, we focused on light and oxygen, the most important external factors in Chl biosynthesis, to investigate their effects on Chl d biosynthesis in A. marina. The amount of Chl d in heterotrophic dark-grown cells was comparable to that in light-grown cells, indicating that A. marina has a light-independent pathway for Chl d biosynthesis. Under anoxic conditions, the amount of Chl d increased with growth in light conditions; however, no growth was observed in dark conditions, indicating that A. marina synthesizes Chl d normally even under such “micro-oxic” conditions caused by endogenous oxygen production. Although the oxygen requirement for Chl d biosynthesis could not be confirmed, interestingly, accumulation of pheophorbide d was observed in anoxic and dark conditions, suggesting that Chl d degradation is induced by anaerobicity and darkness.

Comparative Genomic Analysis of the Marine Cyanobacterium Acaryochloris marina MBIC10699 Reveals the Impact of Phycobiliprotein Reacquisition and the Diversity of Acaryochloris Plasmids

“…Recently, MB10699 and MB11017 were reported to differ in their ability to use exogenous carbon sources [ 10 ]. For example, MB10699 was capable of mixotrophic growth with sucrose and glucose as carbon sources, whereas MB11017 was lethal in cultures with these carbon sources.…”

“…Total pigments from Acaryochloris cells were extracted according to the previous report [ 10 ]. After adding methanol to the collected cells (final 90% ( v / v )), the cells were disrupted by sonication (TOMY UD-201; output: 3, duty: 30, 10 s; TOMY, Tokyo, Japan) and then left on ice for 30 min for pigment extraction.…”

Recent Reports on Bioactive Compounds from Marine Cyanobacteria in Relation to Human Health Applications

“…Chlorophylls are some of the most abundant photosynthetic pigments present in marine cyanobacteria. Chlorophyll a is the major type of chlorophyll found in cyanobacteria, while some cyanobacteria species have been reported to possess additional chlorophylls, such as Chlorophyll d and Chlorophyll f [ 55 ]. Chlorophylls derived from cyanobacteria could be structurally altered into various derivatives: pheophorbides, pheophytin, porphycene, porphyrins, and phthalocyanines [ 56 , 57 ].…”