Presence of lipids in mycobacteriophage i3.

The presence of lipids has been demonstrated in mycobacteriophage I3. The total lipid was composed of 69% phospholipids and 31% neutral lipids. More than two-thirds of phospholipids present in the phage were synthesized in the host prior to infection. The fatty acid composition of the phage differed markedly from that of its host, both in chain length and the degree of saturation. The phage lipid was mostly composed of saturated fatty acids of which more than 50% were short chain fatty acids. Changes in growth temperatures reflected variations in fatty acid composition, characteristic of the phage, and which were distinctly different from those of the host. Electron microscopic observations revealed that the phage has a membranous bilayer structure. The presence of lipids may facilitate the phage-host interaction especially in lipid-rich organisms like mycobacteria.