1 Chlorophylls in Microalgae: Occurrence …
5
Evolution process distributed the Chl a, b, c, d, and f among the various groups of
microalgae, and their presence or absence is of taxonomic importance (Ritchie 2006).
Table 1.1 shows the taxonomic distribution of chlorophylls (Chl) in microalgae.
Chlorophyll b is present in Chlorophyta (green algae) and Euglenophyta; chlorophyll c is present in Bacillariophyta, Phaeophyta, Pyrrophyta, and Cryptophyta;
chlorophyll d is present only in Rhodophyta (van den Hoek et al. 1995). This
pigment is present in the prochlorophytes, green algae, and green plants (Scheer
1991). Chlorophyll c is widely distributed and abundant in the Chromophyte algae
and diatoms, and usually consists of a mixture of two components c 1 and c 2 (van den
Hoek et al. 1995). The two pigments differ only in two hydrogen atoms, Chl c 1 (Mg
tetradehydro-pheoporphyrin) that has an ethyl group, and Chl c 2 (Mg hexadehydropheoporphyrin) that has a vinyl group at position C4 in ring II of the chlorophyll
macrocycle (Strain et al. 1971, Wright and Jeffrey 2006). Chl c including its two
components (Chl c 1 and Chl c 2 ) differ from Chls a and b in several important aspects:
they are porphyrin rather than chlorin derivatives with ring IV unsaturated; they
contain an acrylic rather than propionic side chain at C7; they occur as free acids
(not esterified to phytol) (Larkum et al. 1994). Chlorophyll c has been considered
an accessory Chl, but now it is better known as light-harvesting chlorophylls, i.e.,
they augment the light-harvesting properties of oxygenic photosynthetic organisms
such as Cyanobacteria, algae, and plants by passing on light excitation to chlorophyll a (Larkum et al. 1994; Larkum and Kühl 2005). Another variety of Chl c is
the Chl c 3 , with high polarity compared to Chls c 1 and c 2 . Chl c 3 has relatively low
absorption in 630 nm in vivo compared to 580 nm. This pigment (Chl c 3 ) is present
in Chrysophyceae, Haptophyta, and diatoms, but in the second it is found together
with unusual fucoxanthin pigments (Stauber and Jeffrey 1988, Fawley 1989, Zapata
et al. 2006). The absorption spectra of chlorophyll c1 and c2 in organic solvents are
of the magnesium-porphyrin type, exhibiting a three-banded spectrum with very low
absorption in the red region, at shorter wavelengths (628 nm) than that of chlorophyll
b (645 nm) and chlorophyll a (660 nm) (Jeffrey 2013).
Chlorophyll d is a pigment that has been reported to occur in a number of species
of the Rhodophyta (red algae), a group that contains Chl a but, at most, only traces of
Chl b (Manning and Strain 1943). The occurrence of Chl d in red algae, together with
the probable absence of Chl b and c, is further evidence for the remoteness of any
phylogenic connection between this large group of algae and most of the other groups
of photosynthetic organisms. Chl d differs markedly from all other chlorophylls due
to absorption spectra in the near-infrared; The Chl d in vivo absorption peak occurs
between 708 and 720 nm (Miyashita et al. 1996, Nieuwenburg et al. 2003, Larkum
and Kühl 2005).
The most recently described chlorophyll, the Chl f , has been reported in
2010 (Chen et al. 2010). As chemical structure of this pigment (Chl f ), the
[2-formyl]-chlorophyll a, was isolated from stromatolites of the specie Halomicronema hongdechloris, Western Australia. The morphological features of stromatolites provide a unique environment for specific but diverse cyanobacterial communities (Chen et al. 2010). Halomicronema hongdechloris is the thinnest filamentous cyanobacterium known to date, which contains not only Chl a, but also Chl
5
Evolution process distributed the Chl a, b, c, d, and f among the various groups of
microalgae, and their presence or absence is of taxonomic importance (Ritchie 2006).
Table 1.1 shows the taxonomic distribution of chlorophylls (Chl) in microalgae.
Chlorophyll b is present in Chlorophyta (green algae) and Euglenophyta; chlorophyll c is present in Bacillariophyta, Phaeophyta, Pyrrophyta, and Cryptophyta;
chlorophyll d is present only in Rhodophyta (van den Hoek et al. 1995). This
pigment is present in the prochlorophytes, green algae, and green plants (Scheer
1991). Chlorophyll c is widely distributed and abundant in the Chromophyte algae
and diatoms, and usually consists of a mixture of two components c 1 and c 2 (van den
Hoek et al. 1995). The two pigments differ only in two hydrogen atoms, Chl c 1 (Mg
tetradehydro-pheoporphyrin) that has an ethyl group, and Chl c 2 (Mg hexadehydropheoporphyrin) that has a vinyl group at position C4 in ring II of the chlorophyll
macrocycle (Strain et al. 1971, Wright and Jeffrey 2006). Chl c including its two
components (Chl c 1 and Chl c 2 ) differ from Chls a and b in several important aspects:
they are porphyrin rather than chlorin derivatives with ring IV unsaturated; they
contain an acrylic rather than propionic side chain at C7; they occur as free acids
(not esterified to phytol) (Larkum et al. 1994). Chlorophyll c has been considered
an accessory Chl, but now it is better known as light-harvesting chlorophylls, i.e.,
they augment the light-harvesting properties of oxygenic photosynthetic organisms
such as Cyanobacteria, algae, and plants by passing on light excitation to chlorophyll a (Larkum et al. 1994; Larkum and Kühl 2005). Another variety of Chl c is
the Chl c 3 , with high polarity compared to Chls c 1 and c 2 . Chl c 3 has relatively low
absorption in 630 nm in vivo compared to 580 nm. This pigment (Chl c 3 ) is present
in Chrysophyceae, Haptophyta, and diatoms, but in the second it is found together
with unusual fucoxanthin pigments (Stauber and Jeffrey 1988, Fawley 1989, Zapata
et al. 2006). The absorption spectra of chlorophyll c1 and c2 in organic solvents are
of the magnesium-porphyrin type, exhibiting a three-banded spectrum with very low
absorption in the red region, at shorter wavelengths (628 nm) than that of chlorophyll
b (645 nm) and chlorophyll a (660 nm) (Jeffrey 2013).
Chlorophyll d is a pigment that has been reported to occur in a number of species
of the Rhodophyta (red algae), a group that contains Chl a but, at most, only traces of
Chl b (Manning and Strain 1943). The occurrence of Chl d in red algae, together with
the probable absence of Chl b and c, is further evidence for the remoteness of any
phylogenic connection between this large group of algae and most of the other groups
of photosynthetic organisms. Chl d differs markedly from all other chlorophylls due
to absorption spectra in the near-infrared; The Chl d in vivo absorption peak occurs
between 708 and 720 nm (Miyashita et al. 1996, Nieuwenburg et al. 2003, Larkum
and Kühl 2005).
The most recently described chlorophyll, the Chl f , has been reported in
2010 (Chen et al. 2010). As chemical structure of this pigment (Chl f ), the
[2-formyl]-chlorophyll a, was isolated from stromatolites of the specie Halomicronema hongdechloris, Western Australia. The morphological features of stromatolites provide a unique environment for specific but diverse cyanobacterial communities (Chen et al. 2010). Halomicronema hongdechloris is the thinnest filamentous cyanobacterium known to date, which contains not only Chl a, but also Chl