After determining morphological
characteristics and phylogenetic classification, it was selected as H. hongdechloris. The last word, . hongdechloris , means “red
chlorophyll” in Chinese. Halomicronema
hongdechloris is the shrillest filamentous cyanobacterium known to date,
which comprises not only Chl a, but also Chl f. The pigment composition was
determined by HPLC and then absorption and luminescence spectra were examined.
Chl a, Chl f, and four types of carotenoids namely zeaxanthin, violaxanthin,
antheraxanthin, and ?carotene were found to be present. The presence of Chl f
to Chl a depends on cultivation conditions. Chl f was shown to be equal to
12.5, 20, or 10% of the total chlorophyll amount in cells cultivated under FRL enlightenment
(with extreme at 720 to730 nm), and its content is reduced to undetectable
levels in cells cultivated under white light. The ratio of carotenoids was also
reduced and the total pigment content was also decreased in cells cultivated
under white light. In this way, cells are assumed to adapt their pigment
composition to utilize ambient light in the most effective way: by accumulating
Chl f to absorb red light under the prevalence of FRL in the incident light,
and phycobiliproteins and Chl a – to absorb in the main white light range. Even
so, finest culture conditions as well as Chl f functions in H. hongdechloris are not yet studied. The contrivance
of alteration of the pigment apparatus is also unclear.


KC1 strain, in
2011, Chl f was revealed in a unicellular cyanobacterium, strain KC1, from the
fresh water Biwa Lake in Japan, Shiga Prefecture. Cells were cultured under several
radiance conditions: under white or far red light (740 nm). In both cases,
pigment investigation was led by normal phase HPLC on silica gel. In cells
grown under white light, a prevalence of Chl.a was found, whereas Chl a, and
Chl f were present as minor pigments. At the same time, Chl f? and Pheo f were
not found, as in the case of other cyanobacteria. only cells grown under FRL
illumination had Chl f as a minor pigment. The function of Chl f in these
cyanobacterial cells is still undetermined. Chl f may function not as a RC or
electron transfer chain intermediary, but as a light harvesting antenna
component. One of the key features of a cyanobacterium capable of photo
acclimation and growth under FRL is the presence of a cluster comprising of 21
genes coding photosynthetic proteins and specifically expressed under FRL. It
is to be noted that the substitution of the electron donor methyl group CH3
in ring I of Chl a by the electron acceptor formyl group CHO of Chl f causes a
shift of the Qy band to longer wavelength as well as its increase, and a short wavelength
shift of the Soret band together with its reduction . Similar effects are
observed for Chl d, whose vinyl group is exchanged by a formyl group in ring
II. Broadening of the absorption band by pigments capable of effective
photosynthesis up to 750 nm is feasible, since light intensity in the 700-750
nm region is not decreased much even at the water depth of 1 m. (S.
I. Allakhverdie et al. August 2015).

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