Chlorophyll f and chlorophyll d are produced in the cyanobacterium Chlorogloeopsis fritschii when cultured under natural light and near‐infrared radiation

Abstract

a b s t r a c tWe report production of chlorophyll f and chlorophyll d in the cyanobacterium Chlorogloeopsis fritschii cultured under near-infrared and natural light conditions. C. fritschii produced chlorophyll f and chlorophyll d when cultured under natural light to a high culture density in a 20 L bubble column photobioreactor. In the laboratory, the ratio of chlorophyll f to chlorophyll a changed from 1:15 under near-infrared, to an undetectable level of chlorophyll f under artificial white light. The results provide support that chlorophylls f and d are both red-light inducible chlorophylls in C. fritschii. Ó 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. IntroductionChlorophyll f, the longest wavelength absorbing chlorophyll of oxygenic photosynthesis, was first discovered in samples taken from a stromatolite and enriched under near-infra red (near-IR) light [1]. A cyanobacterium was subsequently isolated and found to produce chlorophyll f when cultured under near-IR, but not white light [2,3]. A chlorophyll f-producing cyanobacterium has also been found in a Japanese Lake [4]. In organic solvent, the absorption spectrum of chlorophyll f shows a relatively large Q Y transition at 706 nm, and a Soret band at 406 nm [1,5].Stromatolite environments like that of the chlorophyll f producing filamentous cyanobacteria, Halomicronema hongdechloris, can be comparatively enriched in near-IR compared to UV/vis wavelengths [6], analogous to habitats of the chlorophyll d-producing cyanobacterium Acaryochloris marina [7][8][9]. Chorophyll d was first discovered in 1943 [10] but was thought to be an artefact of extraction for many years [11]. Chlorophyll d has been mistakenly associated with red algae in the past [10,12], whereas it is now known to be produced by epiphytic Acaryochloris sp. growing on red algae [13]. Chlorophyll d is the major chorophyll in A. marina [14,15]. Like chlorophyll f, chlorophyll d also has a red-shifted Q Y transition (696 nm) compared to chlorophyll a [5,16], enabling light harvesting in the near-IR region [17,18].Chlorogloeopsis fritschii is a subsection V cyanobacterium [19] which has a diverse morphology and diversity of function [20][21][22]. With a tolerance to a variety of growth conditions [22], and being amenable to large-scale culture, C. fritschii has potential for biotechnological applications [23,24]. We report production of chlorophyll f and chlorophyll d in the cyanobacterium C. fritschii cultured under near-IR and natural light conditions. We discuss these findings in context of the organism's natural habitat, morphotype and genome sequence.

Novel chlorophylls and new directions in photosynthesis research

“…Aseriate cells dominate under light condition of infrared light and natural light (Airs et al 2014). C. fritschii is able to synthesise six carotenoids and three chlorophylls (Chl a, Chl d and Chl f) (Airs et al 2014). We note that the production of Chl f and Chl d are found in C. fritschii grown under both infrared light and natural light conditions (Airs et al 2014).…”

“…Further, Chl f is the first chlorophyll known in which its biosynthesis is directly induced by infrared light . More recently, Chl f was reported in other cyanobacteria (Akutsu et al 2011;Airs et al 2014;Gan et al 2014;Miyashita et al 2014).…”

“…JSC-1 and Chlorogloeopsis fritschii PCC 6912 (Akutsu et al 2011;Airs et al 2014;Gan et al 2014). H. hongdechloris belongs to the genus Halomicronema based on phylogenetic analysis and morphological features ).…”

“…This infrared-light-inducible synthesis of Chl f appears to be the case for the other recent discoveries of Chl f-containing organisms: cyanobacterium strain KC1 (Akutsu et al 2011), Leptolyngbya sp. JSC-1 (Gan et al 2014) and Chlorogloeopsis fritschii PCC 6912 (Airs et al 2014). Cyanobacterium strain KC1 is a unicellular cyanobacterium; it is closely related to unicellular cyanobacteria Aphanocapsa muscicola and has a sister relationship to clade of Acaryochloris spp.…”

“…C. fritschii has a diverse morphology and diversity of function depending on growth conditions (Evans et al 1976), such as filaments and aseriate forms of irregular clumps of cells. Aseriate cells dominate under light condition of infrared light and natural light (Airs et al 2014). C. fritschii is able to synthesise six carotenoids and three chlorophylls (Chl a, Chl d and Chl f) (Airs et al 2014).…”