Unique chlorophylls in picoplankton Prochlorococcus sp. “Physicochemical properties of divinyl chlorophylls, and the discovery of monovinyl chlorophyll b as well as divinyl chlorophyll b in the species Prochlorococcus NIES-2086”

Abstract

In this review, we introduce our recent studies on divinyl chlorophylls functioning in unique marine picoplankton Prochlorococcus sp. (1) Essential physicochemical properties of divinyl chlorophylls are compared with those of monovinyl chlorophylls; separation by normal-phase and reversed-phase high-performance liquid chromatography with isocratic eluent mode, absorption spectra in four organic solvents, fluorescence information (emission spectra, quantum yields, and life time), circular dichroism spectra, mass spectra, nuclear magnetic resonance spectra, and redox potentials. The presence of a mass difference of 278 in the mass spectra between [M+H] and the ions indicates the presence of a phytyl tail in all the chlorophylls. (2) Precise high-performance liquid chromatography analyses show divinyl chlorophyll a' and divinyl pheophytin a as the minor key components in four kinds of Prochlorococcus sp.; neither monovinyl chlorophyll a' nor monovinyl pheophytin a is detected, suggesting that the special pair in photosystem I and the primary electron acceptor in photosystem II are not monovinyl but divinyl-type chlorophylls. (3) Only Prochlorococcus sp. NIES-2086 possesses both monovinyl chlorophyll b and divinyl chlorophyll b, while any other monovinyl-type chlorophylls are absent in this strain. Monovinyl chlorophyll b is not detected at all in the other three strains. Prochlorococcus sp. NIES-2086 is the first example that has both monovinyl chlorophyll b as well as divinyl chlorophylls a/b as major chlorophylls.

Dynamic macromolecular composition and high exudation rates in Prochlorococcus

“…The emergence of the DVchlA-like pigment is currently unexplained, although this pigment may be an epimerization product of DVchlA (DVchlA'). DVchlA' has been previously observed in several Prochlorococcus strains (Komatsu et al 2016), and a peak in HPLC chromatograms that may also be a similar derivative has been observed in samples from the Sargasso Sea (Goericke and Welschmeyer 1993). In our study, the DVchlAlike pigment is associated with culture decline.…”

“…2d) but was not one of the known degradation products (pheophytin-A eluted later, whereas pheophorbide A, chlorophyllide A and divinyl protochlorophyllide A all eluted much earlier, consistent with the loss of the phytol moiety). Assuming a similar molar absorption rate as DVchlA, this pigment (which may be a DVchlA', an epimerization product of DVchlA, Komatsu et al 2016) comprised as much as 21% of the total DVchlA pigments on day 15, at the end of the decline stage. Importantly, pigments with the same elution time and absorbance were repeatedly observed in samples collected from the oligotrophic Eastern Mediterranean Sea where Prochlorococcus contributes a significant fraction of the phototrophic biomass (Man-Aharonovich et al 2010), as demonstrated in Fig.…”

The distribution of divinyl chlorophylls a and b and the presence of ferredoxin-NADP+ reductase in Prochlorococcus marinus MIT9313 thylakoid membranes

“…Versus other oxygenic photosynthetic organisms, MIT9313 has a higher content of Chl b 2 [15, 30, 50, 51]. The prochlorophytes together with green algae and plants have a peripheral light-harvesting antenna integrated into the membrane that shares the use of chlorophyll b in their photosynthetic apparatus.…”

Photo-Oxidative Protection of Chlorophyll a in C-Phycocyanin Aqueous Medium

“…Figure 2 shows APCI-MS spectra acquired in the m/z range of 850-910 before (top) and after (bottom) 4 h light illumination of extracts from C. vulgaris in three different media, namely, EtOH, DW, and C-PC. In this m/z range, four peaks occurred at 869.5, 871.5, 885.5, and 887.5 in ascending order (note that the peaks indicate monoisotopic peaks of the corresponding molecular species ), and these peaks were assigned to divinyl pheophytin a (DV-PHEa), pheophytin a (PHEa), hydroxydivinyl pheophytin a (OH-DV-PHEa), and hydroxy pheophytin a (OH-PHEa), respectively, based on the results of previous studies [13,49,50] (see Table 1 and Figure 3). In APCI-MS spectra, molecular species with Mg 2+ such as chlorophyll a, divinyl chlorophyll a, and hydroxydivinyl chlorophyll a were not detected as Mg 2+ is rapidly removed under the applied acidic APCI-MS conditions.…”