CYANOPHAGES - Cyanobacteria - page 423

of M . aeruginosa . Cyanophages phylogenetically related to Ma-LMM01 infecting M . aeruginosa have
been analysed by amplifying by real-time PCR the ribonucleotide reductase α-subunit, ribonucleotide
reductase β-subunit and sheath protein genes (ORFs 090, g91 and ORF092) with primers specially
developed for these genes. The prevalence of the phage sequences relating to cyanophages Ma-
LMM01, Ma-LMM02, Ma-LMM03 and Ma-HPM05 were noted when the blooms of Microcystis were
represented in Hirosawanoike Pond and Lake Mikata. However, no lytic phages active against M .
aeruginosa strain NIES298 could be isolated (Takashima et al ., 2007). One of the probable reasons
suggested is that Ma-LMM01 may enter into a lysogenic cycle. A supporting evidence in favour of
this is the recognition of Ma-LMM01 phage-specifi c insertion sequence elements (IS607-cp) in four
strains of M . aeruginosa (NIES90, NIES112, NIES604 and RM6) and in the genome of Cyanothece sp.
The insertion element IS607-cp is present in multiple copies in the four strains of M . aeruginosa and
depending on the location on their genomes three groups of IS607-cp have been recognized. While
IS607-cp-1 is present in three strains (NIES90, NIES112 and NIES604), IS607-cp-2 and IS607-cp-3 are
found specifi c to NIES90 and RM6, respectively (Kuno et al ., 2010).
Adolph and Haselkorn (1971) isolated cyanophage N-1 that infects the nitrogen-fixing
cyanobacterium Nostoc muscorum . The viral particles are polyhedral with a contractile tail attached
to the head by a tail capital similar to LPP-1. The diameter of the head is 55 nm which contains
DNA with a molecular weight of 38 x 10 6 daltons and G+C content of 41%. In mature N-1 virion a
total of 19 structural proteins were resolved with a molecular weight of 37,000 and 14,000 daltons.
It would require about 34% of the coding capacity of N-1 DNA which is similar to LPP-1 (Sherman
and Haselkorn, 1970c; Adolph and Haselkorn, 1973b). A cyanophage that infects a Synechococcus sp.
has been isolated along with its host from a reservoir in Korea bearing morphological resemblances
to AS-1 (Kim and Choi, 1994). Koz'yakov (1981) described a new cyanophage S-3L active against
Synechococcus schmidlea . The phage head has a diameter of 81.6 nm and a tail of 16.3 nm long with
a contractile sheath. The phage DNA contains 46.8 to 47.6 mol% G+C. The adsorption time was
60 minutes with a latent period and eclipse period of 11 and 4 h, respectively. The burst size was
approximately 35 particles per infected cell.
III. FRESHWATER CYANOSIPHOVIRUSES
S-1, the type species of the genus Cyanosiphovirus, infecting Synechococcus has been isolated by
Adolph and Haselkorn (1973a). This phage has an isometric head with a diameter of 50 nm and a rigid
non-contractile tail of 140 nm long. The genome of the phage is dsDNA with a molecular weight of
23-26 x 10 6 and a G+C content of 70-74%. There are 13 structural proteins of which the major structural
proteins have molecular weights of 39,000, 11,000 and 10,000. Another Synechococcus phage S-(2)L,
isolated from Russia by Khudyakov (1977), also possesses an isometric head that is slightly larger
(56 nm in diameter) with a non-contractile tail (120 nm long) but possesses several short thin fi bers
at the distal end. The molecular weight of dsDNA is 26 x 10 6 . Khudyakov et al . (1978) reported that
adenine in this phage DNA is substituted by 2,6-diaminopurine. Other cyanosiphoviruses that infect
Synechococcus are S-4(L) and S-5(L) which have been reported by Khudyakov and Matveyev (1981,
1982). Another related member of this group is SM-2 that infects Synechococcus and Microcystis . It
also has an isometric head that is 50-55 nm in diameter with a fl exible non-contractile tail of 130-140
nm long (Fox et al ., 1976; Leach et al ., 1980). A cyanosiphovirus with a capsid diameter of 70 nm and
a long non-contractlie tail, infecting the bloom-forming toxic cyanobacterium Cylindrospermopsis
raciborskii , has been reported from Australian freshwater lakes (Pollard and Young, 2009). The latent
period of this has been reported to be 21 h with a burst size of 64 phage particles per cell.