Bacteriophage Morphological Characterization by Using Transmission Electron Microscopy

Abstract

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.

Isolation and characterization of lytic bacteriophages from various sources in Addis Ababa against antimicrobial-resistant diarrheagenic Escherichia coli strains and evaluation of their therapeutic potential

“…SEM analysis is a rapid and simple method of characterizing phages, aiding in the identification of novel phages and attribution to families [ 36 ]. SEM observation indicated that 4 out of 17 phages, isolated from different samples, belonged to the order Caudovirales , with 2 of the isolates being part of the Myoviridae family.…”

Isolation and characterization of bacteriophages for combating multidrug-resistant Listeria monocytogenes from dairy cattle farms in conjugation with silver nanoparticles

“…No LMPs were isolated from manure or silage samples from farm I, which may be attributed to a high level of hygiene and the frequent removal of manure. Bacteriophages are common and reliable indicators of bacterial contamination because their occurrence is high in surroundings where their hosts are numerous [ 28 ]. The high occurrence of LMPs in silage samples shows that inadequately fermented silage, as well as dairy farm environments in general, are suitable substrates for LMP isolation.…”

“…The classification of isolated phages was based on the morphology observed under TEM, which plays a key role in phage characterization [ 28 , 30 ]. The classification was based on the characteristics of the head and the tail of the phage.…”

“…LMP3 had the shortest tail and was the most infective phage. The length of the tail provides an insight into the phage stability and resistance in the wild; short and non-tailed phages are more resistant, while lengthy tails are more easily destroyed, resulting in phage infectivity loss [ 28 ].…”

Isolation and characterization of lytic bacteriophages from various sources in Addis Ababa against antimicrobial-resistant diarrheagenic Escherichia coli strains and evaluation of their therapeutic Potential

“…SEM analysis is a rapid and simple method of characterizing phages, aiding in the identification of novel phages and attribution to families [12]. SEM observation indicated that 4 out of 17 phages, isolated from different samples, belonged to the order Caudovirales, with 2 of the isolates being part of the Myoviridae family.…”