Application of Phages

Simple drop cast method for enumeration of bacteriophages

Phage enumeration is a basic prerequisite for application of phages in industrial, medical and other processes. Double layer agar (DLA) plaque assay is the classical method employed for isolation, detection as well as enumeration of phage particles in a solution. However, DLA method is considered cumbersome due to its specific temperature requirements and need for one petriplate with two agar layers for each phage sample. We are proposing a drop cast method for enumeration of phages which is comparatively easier and cost effective than classical DLA method as single layer of agar without any specific temperature condition is required. Added advantage of this method is that 7-10 dilutions of phage suspension can be enumerated on a single agar plate in contrast to one dilution per plate as required in DLA method. Although standard deviation in phage count was higher in the proposed method than DLA method, still drop cast method provided first-approximation phage titer which can be further validated by DLA method for more accuracy. Hence, the present method can be considered reliable, easy and cost effective for determining approximate phage count in an unknown phage suspension.

Probing the viral metallome: searching for metalloproteins in bacteriophage λ-- the hunt begins

Although the proteome and genome of bacteriophages are well developed, there is little knowledge about metals and their interactions with the phages, even though metals have been observed in stabilizing phage particles. With expanding studies of phage display and its promising applications, metalloprotein investigations in the bacteriophage areas are necessary to understand whether or not metalloproteins are included in the viral coat proteome. Since these virus studies are still in their infancy, lambda phage was chosen due to its high metal-binding potential as suggested by the cysteine/methionine rich proteins in the viral coat. After large-scale preparation and further purification of lambda phage according to standard protocols, state-of-the-art metallomics techniques via combinations of chromatographies and mass spectrometries were utilized for screening metal-associated species in lambda phage. The lambda phage sample was first separated using non-denaturing size exclusion chromatography with selective metal detection by ICPMS for screening associated metals and generating size distribution fractions for the various metal species, some of which include metalloproteins. Various molecular size distribution patterns were exhibited for the metals detected, Mn, Fe, Co, Ni, Cu and Zn, at different molecular weight ranges. On the other hand numerous other metals were not associated with the coat proteins, as they were not detected in the different molecular weight fractions. Further identification for putative metallopeptides and metalloproteins was accomplished by collecting various metal species' fractions offline and subsequently analyzing tryptically-digested fractions via nanoLC-Chip-ESI-MS. By searching appropriate MS databases with both Spectrum Mill and MASCOT search engines, the main capsid protein, gpE, a capsid decoration protein, gpD, and main tail component protein, gpV, were found and are known for associations with the detected transition metals. These findings will likely provide valuable information for lambda phage engineered applications.