Bacteriophage Morphological Characterization by Using Transmission Electron Microscopy

Bacteriophages or more commonly “phages” are bacterial viruses. They are ubiquitous and good indicators of bacterial contaminations since their prevalence is high in those environments where their hosts are abundant. Phage classification is based on morphology and for this reason, even though it is considered an old technique, TEM (Transmission Electron Microscopy) still plays a key role in their characterization. In the present work, the authors focused on TEM analysis of phage ɸApr-1 isolated against Lactococcus lactis (L. lactis), implicated in industrial fermentations and of phage ɸIZSAM-1, active against Listeria monocytogenes (L. monocytogenes), isolated from the environment. For observation with TEM (EM 900T-Zeiss), phages were harvested in liquid media and were negative stained with fosfotungstic acid 2‰. An accurate viral ultrastructure analysis by using TEM is fundamental not only in the first approach of characterization of newly isolated phages but also for providing useful information to go further to the selection process as potential bio-decontaminants.