Description

Bacteriophages are bacterial viruses and have been used for almost a century as antimicrobial agents. In the West, their use diminished when chemical antibiotics were introduced, but they remain a common therapeutic approach in parts of Eastern Europe. Increasing antibiotic resistance in bacteria has driven the demand for novel therapies to control infections and led to the replacement of antibiotics in animal husbandry. Alongside this, increased pressure to improve food safety has created a need for faster detection of pathogenic bacteria. Hence, there has been a resurgence of interest in bacteriophage applications, and this has encouraged the emergence of a large number of biotech companies hoping to commercialize their use. Research in Europe and the United States has increased steadily, leading to the development of a range of applications for bacteriophage agents for the healthcare, veterinary and agricultural sectors. This article will attempt to answer the question of whether bacteriophages are now delivering on their potential.

Evolution of Phages

Bacteriophages are classified into one order and 13 families. Over 5100 phages have been examined in the electron microscope since 1959. Bacteriophages occur in over 140 bacterial or archaeal genera. Their distribution reflects their origin and bacterial phylogeny. Bacteriophages are polyphyletic, arose repeatedly in different hosts, and constitute 11 lines of descent. Tailed phages appear as monophyletic and as the oldest known virus group. Phages, bacterial viruses are the most numerous microorganisms on Earth. Bacteria have developed an astonishing array of strategies to combat these viruses at each step of the infection process. Here we describe these strategies and how phages have adapted to subvert them. There are at least three strategies used by adsorption-blocking systems: receptor blocking, extracellular matrix production and competitive inhibitor production. Superinfection Exclusion systems prevent phage DNA entry into the host cell, thereby conferring bacterial immunity against superinfecting phages. Several mechanisms that inhibit phage DNA injection have been uncovered in Gram-negative and Gram-positive bacteria. The notorious bacterial restriction–modification systems prevent phage infection by cleaving phage genomic DNA. As a response, phages have evolved by specifically modifying their genomes to avoid DNA cleavage. This ongoing battle of co-evolution between bacteria and phages is exemplified by the canonical coli phage T4. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and CRISPR-associated (case) genes are new fascinating topics. The bacterial and archaeal CRISPR–CA’s systems confer immunity against incoming foreign DNA such as phage genomes. A likely mode of action of this mechanism has been proposed, along with phage strategies to circumvent this system. Bacteria have also evolved a plethora of intracellular proteins that cause abortion of the phage infection.

Further Prospects

The phylogeny of infections has evaded ages of virologists. Current techniques have reclassified the inquiries instead of accomplished conclusive responses. In firmly related gatherings, confines can be set up by the level of closeness, yet whether all infections or even all phages comprise a monophyletic bunch stays unsure. The advancement of thoughts, beginning in the pre genome period, is represented by work on phages and their family members. During the 1950s, various mild phages lambdoid were found morphologically and could recombine with it. Electron microscopy of heteroduplexes, combined with the outcomes from hereditary crosses, checked that the lambdoid phages have a typical hereditary guide however show different specificities for properties, for example, reconciliation, constraint and host range. These examinations additionally showed that any two lambdoid phages are comparable in certain sections of their genomes and divergent in others, with unexpected changes from similitude to divergence. Looking at all the known lambdoid phages, there is little uncertainty that they have gone through broad recombination in nature, blending and matching heterologous explicitness determinants. Sequencing likewise confirms the sharpness of most limits between sections of close comparability and those of outrageous divergence. In any case, breakage and joining now and again happen regardless of whether there is no homology which addresses new ground and throughout transformative time this happens frequently to the point of creating the sharp limits among homology and nonhomology that are seen in phages. Most such new intersections ought to be deadly or injurious, yet normal determination has protected a few harmless blends. Bacteriophages otherwise called phages are infections that taint microbes. Similarly as with all infections, phages are irresistible particles that have something like two parts: nucleic corrosive and protein. On the off chance that a phage attacks a vulnerable bacterial cell, the phage or if nothing else its nucleic corrosive enters the cell and triggers a pattern of phage creation.