CYANOPHAGES - Cyanobacteria - page 427

M . aeruginosa in Furuike pond that represents a hypereutrophic pond. Although fi ltered pond waters
caused lysis of the host cells in cultures, it was not possible to isolate the viral particles. Selective
amplifi cation of the genetic material of the agents followed by pulse-fi eld gel electrophoresis (PFGE)
demonstrated the presence of viral communities differing in genome sizes.
VI. STABILITY
Safferman and Morris (1964a) reported that LPP-1 retains about 70% of its initial activity when
stored in its own lysate at 4°C while the requirement of Mg 2+ for its infectivity was subsequently
demonstrated (Schneider et al ., 1964; Goldstein et al ., 1967). Cyanophages SM-1, AS-1 and S-2L are
stable in distilled water and Mg 2+ is not required for stability or infectivity (Safferman et al ., 1969b;
1972; Khudyakov, 1977). Safferman et al . (1969b) noted no signifi cant loss in the viability of SM-1
phage, when stored at 4°C. Moreover, SM-1 is identical to LPP-1 in its requirement to pH and thermal
stability. Cyanophages AC-1 and TAuHN-1 have been reported to be stable in their own lysates
at 4°C (Venkataraman et al ., 1973; Kaushik and Venkataraman, 1973). Amla (1978) reported slight
inactivation of AS-1 by EDTA and sodium citrate that has been found to be concentration-dependent.
Studies on the effects of metallic ions on the stability of N-1 indicated that the growth medium of
the host (modifi ed Chu-10 medium) and saline magnesium chloride conferred total stability to the
virus N-1 (Padhy and Singh, 1978a).
VII. ADSORPTION
The time taken for nearly 95% of the cyanophage particles to get adsorbed to the host cell wall
varied from cyanophage to cyanophage. Although LPP-1 is stable in its own lysate, it needs Mg 2+
for its biological activity (Schneider et al ., 1964; Goldstein et al ., 1967). This apparently refl ects the
requirement of Mg 2+ for adsorption. Moreover, SM-1 and AS-1 do not require Mg 2+ for infectivity
(Safferman et al ., 1969a, 1972). No special requirements for adsorption of cyanophages LPP-2
and D-1 have been reported (Safferman et al ., 1969b; Daft et al ., 1970). The effect of physical and
chemical agents on adsorption of N-1 phage has been studied (Padhy and Singh, 1977a).The effect
of temperature on the adsorption and one-step growth of N-1 was described by Padhy and Singh
(1977b). The age of host, ions and pH have been shown to infl uence adsorption of N-1 to the cells of
N . muscorum (Padhy and Singh, 1978b). The rate of adsorption of N-1 was reduced with the aging of
algal cultures and complete loss of adsorption occurred when dead algal cells were used. Further,
N-1 did not require the presence of saline-magnesium chloride, L-tryptophan and L-phenylalanine
for adsorption and optimum pH for adsorption of N-1 was noted to be 7.6-8.1 (Padhy and Singh,
1978b). The involvement of host polysaccharides in AS-1 adsorption has been indicated (Samimi
and Drews, 1978). The adsorption of AS-1 was enhanced in dark by increasing the concentration of
sodium (Cseke and Farkas, 1979).
Bobrovnik et al . (1978) studied the kinetics of adsorption of cyanophage A-1 and suggested an
enzymatic character of virus adsorption. Illumination and concentration of sodium in the external
medium enhanced the adsorption of phage AS-1 to A . nidulans while illumination alone doubled phage
adsorption at normal sodium concentration (Na = 11.7 mM). An increase of sodium concentration
(Na = 0.11 mM) resulted in a 10-fold increase in phage adsorption in darkness (compared to that
found in light) (Cseke and Farkas, 1979). Olivera et al . (1982) reported the adsorption of AS-1
cyanophage to vesicles of known lipid composition especially phosphatidecholine (from soybean)
and cholesterol but not the algal lipids.