![]() In addition, an interaction with the bacterial capsule is also evident for some phages belonging to other phage families. The majority of bacteriophages, which rely on bacterial polysaccharides for infection, belong to the Podoviridae family. However, the steps between capsule binding and cleaving and finally phage DNA injection into the host cell still remain unclear. Capsules should therefore be regarded as the primary receptor of such phages. This indicates that these phages do not only overcome the capsule barrier – they highly depend on it for host recognition and infection. Bacteria lacking the capsular antigens cannot be infected by these phages. After contact with the next physical barrier, the cell wall, the DNA is injected and the bacterium is successfully infected. These phages bind and digest CPS and EPS antigens, thereby drilling a tunnel through the capsules. Other phages, however, adapted to this challenge. In mutant strains lacking the protective capsule, adsorption of these phages is significantly increased. In these cases, the capsule sterically inhibits the adsorption of the phages to the primary phage receptor. CPS and EPS layers can reduce the efficacy of plating of some bacteriophages. LPS very often serves as a ligand for phage tail fiber proteins during adsorption to the host cell membrane. This is why bacteriophages and phage-derived enzymes became a promising alternative for detection and control of bacterial pathogens in agriculture, food, and medical applications.īacterial cell surface decorating polysaccharides, e.g., capsular polysaccharides (CPS), exopolysaccharides (EPS) or lipopolysaccharide (LPS), exhibit important functions in biofilm production, virulence, and in the interaction with bacteriophages. Due to the high host specificity, the accompanying microflora of a target bacterium remains unharmed during phage attack. In many cases, a bacteriophage infects a particular serotype of the target bacterium only. This adsorption process mostly determines host specificity. The infection begins with the adsorption, the recognition of specific ligands at the host surface by tail fiber or tail spike proteins (TSPs). Phage Encoded Depolymerases Cleave Surface Decorating Polysaccharides of Bacteriaīacteriophages (phages) are viruses, which infect bacteria.
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