Microbiology Procedure

Index >> Bacteriophages - Part One >> ssDNA Phages

ssDNA Phages

	ssDNA Phages - The ssDNA phages are two of morphological types icosahedral (isometric) phages and helical (filamentous) phages. Icosahedral phages. The best known example of the icosahedral ssDNA phages is φX174. Other icosahedral phages include φR, α3, St-I,6SR, BR2, U3 and the G series (G4, G6, G13, GI4). These phages do not differ in any fundamental way from φXI74.
Helical (filamentous) phages. The filamentous phages are divided into three groups. i) The Pf group (F-specific filamentous phages) all adsorb to the tip of the F -type sex pilus and include fd, fl, MI3,ZJj2, Ec9, AE2, HR and 8A phages. ii) The If group represented by If1 andlf2 adsorb to I-type sex pili specified by the R factor (transmissible drug resistance factor).
iii) The third group includes IKe. These phages are physically similar to Ff phages, but are serologically distinct and with different host specificity. They are specific for strains carrying Rfi- Sex factors. Pf1 and Pf2 isolated from Pseudomonas aeruginosa are the longest known filamentous phages. Xf isolated from Xanthomonas oryzae is morphologically similar to Fr, but has a different DNA base composition.

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