The Virulence Index: A Metric for Quantitative Analysis of Phage Virulence.

One of the main challenges in developing phage therapy and manufacturing phage products is the reliable evaluation of their efficacy, performance, and quality. Since phage virulence is intrinsically difficult to fully capture, researchers have turned to rapid but partially inadequate methods for its evaluation. This study demonstrates a standardized quantitative method to assess phage virulence based on three parameters: the virulence index ( )-quantifying the virulence of a phage against a host, the local virulence ( )-assessing killing potential at given multiplicities of infection (MOIs), and -the MOI at which the phage achieves 50% of its maximum theoretical virulence.

Modeling tailed bacteriophage adsorption: Insight into mechanisms.

The process of a bacteriophage attaching to its host cell is a combination of physical diffusion, biochemical surface interactions, and reaction-induced conformational changes in receptor proteins. Local variations in the physico-chemical properties of the medium, the phage׳s mode of action, and the physiology of the host cell also all influence adsorption kinetics. These characteristics can affect a specific phage׳s binding capabilities and the susceptibility of the host cell to phage attack.

Evidence that the heterogeneity of a T4 population is the result of heritable traits.

Many bacteriophage populations display heterogeneity in their adsorption characteristics; a portion of the phage population remains free in solution throughout adsorption experiments (residual fraction). This residual fraction generally constitutes a minority of phages that exhibit significantly slower adsorption kinetics than the main phage stock (main fraction). While this phenomenon is likely the result of evolutionary driving forces, the present study demonstrates that the residual fraction is not always the result of phenotypic variations within a single genotype, as is generally thought.

A simple and rapid protocol for measuring neutral lipids in algal cells using fluorescence.

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal fermentation processes and screening for new oil-rich strains requires a fast and reliable protocol for determination of intracellular lipid content. Current practices rely largely on gravimetric methods to determine oil content, techniques developed decades ago that are time consuming and require large sample volumes.

Impact of the cell life-cycle on bacteriophage T4 infection.

Synchronized Escherichia coli cultures were infected with bacteriophage T4 at discrete points in the cell growth cycle. The cell cycle had a significant impact on the outcome of infection. Cell burst size was smallest for newly formed cells and increased dramatically as these progressed in the cell cycle.

Self-cycling operation increases productivity of recombinant protein in Escherichia coli.

Self-cycling fermentation (SCF), a cyclical, semi-continuous process that induces cell synchrony, was incorporated into a recombinant protein production scheme. Escherichia coli CY15050, a lac(-) mutant lysogenized with temperature-sensitive phage λ modified to over-express β-galactosidase, was used as a model system. The production scheme was divided into two de-coupled stages.

Bacteriophage adsorption efficiency and its effect on amplification.

Existing models for bacteriophage adsorption are modified with the addition of a new term, adsorption efficiency, and applied to a T4-Escherichia coli system. The adsorption efficiency is the fraction of phage that adsorbs irreversibly to the host. Adsorption kinetics were modeled using the adsorption rate constant(k) and the adsorption efficiency(epsilon).