Page 155 - The Biochemistry of Inorganic Polyphosphates

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Cyanobacteria (blue–green algae) and other photosynthetic bacteria 139
fact indicated that in cyanobacteria, as in other bacteria, there are mechanisms of PolyP
involvement in the overcoming of nutrition stresses.
The distribution of PolyPs between different fractions in cyanobacteria depends on cul-
ture age and growth conditions. For example, in Anabaena flos-aquae phosphorus is stored
in different fractions depending on the nitrogen source. Under N 2 fixing conditions, P is
stored as sugar P, whereas with nitrate as the N source it is stored as PolyP (Thompson
et al., 1994).
X-ray dispersive microanalysis (Sicko-Goad et al., 1975; Baxter and Jensen, 1980a) com-
bined with electron microscopy, established the phosphate nature of granules and showed
that appreciable amounts of K and comparatively low quantities of Ca 2+ and Mg 2+ were
+
present in the PolyP granules of cyanobacteria under ordinary cultivation conditions. Under
special conditions, when the medium contained an excess of some metals such as Mg ,
2+
Ba ,Mn 2+ or Zn 2+ and some heavy metals, they accumulate in large quantities in the PolyP
2+
granules (Jensen et al., 1982). Str 2+ was found to accumulate in the cells of cyanobacteria,
but in other inclusions containing sulfur instead of phosphorus.
X-ray microanalysis of thin cryosections of Anabaena cylindrica showed that aluminium
wasrapidlytakenupandaccumulatedinPolyPgranules(Petterssonetal.,1985).Inaddition,
aluminium was found in the cell walls but could not be detected in the cytoplasm. The con-
centration of phosphorus in the medium affected the accumulation pattern. More aluminium
was bound with PolyP granules and with the cell walls after growth in a P i -rich medium.
Some evidence was obtained that the cells of Anacystic nidulans with a high PolyP
content showed a greather tolerance to Cd 2+ than those cells with a small PolyP reserve
(Keyhani et al., 1996). Thus, the accumulation of metal cations in the PolyP granules of
cyanobacteria may function as a detoxification mechanism.
Some cyanobacteria possess cyanophycin, which is a copolymer of aspartic acid and
arginine (Lawry and Simon, 1982). This copolymer is accumulated in the granules, and its
localization in complexes with PolyP is not improbable.
Asregardsotherphotosynthezingbacteria,PolyPmetabolismwasinvestigatedinChloro-
bium thiosulfactophillum (Fedorov, 1959, 1961; Shaposchnikov and Fedorov, 1960; Hughes
et al., 1963; Cole and Huges, 1965). The accumulation of PolyP in the course of culture
development was studied (Fedorov, 1959; Shaposhnikov and Fedorov, 1960). It was shown
that the maximal accumulation of PolyP occurred in the stationary phase. During culture
growth, the proportion of acid-soluble to acid-insoluble PolyPs shifted towards the latter.
Large amounts of acid-soluble PolyPs were accumulated in this bacterium when cells were
illuminated in the absence of CO 2 (Fedorov, 1959). It was suggested that PolyPs were used
as an energy store in the absence of CO 2 fixation.
In another phototrophic bacterium, Rhodospirillum rubrum, a massive pyrophosphate
(PP i ) biosynthesis by photosynthetic phosphorylation was shown (Baltscheffsky, 1967a,b,c,
1969; Baltscheffsky et al., 1966; Keister and Yike, 1967a,b; Keister and Minton, 1971, 1972;
Kulaev et al., 1974a). It was demonstrated that, when Rh. rubrum was grown anaerobically
in light, its chromatophores accumulated salt-soluble PolyPs in addition to PP i (Kulaev
et al., 1974). The PolyPs in chromatophores may be synthesized from ATP (Shadi et al.,
1976) or from PP i (Ok Duck-Chenn and Lee Hynn-Soon, 1987).
It should be pointed out (Kulaev et al., 1974a) that in Rh. rubrum, both in the dark
and in the light, the accumulation of PolyP took place not only in salt-soluble but also
in alkali-soluble and hot-perchloric-acid-extractible fractions. The total amounts of PolyP