Endolysis

Endolysis refers to the lysis of a bacterial cell driven by endolysins, enzymes encoded by bacteriophages during the lytic cycle. The term is used mainly in phage biology and microbiology to describe lysis from within the cell as opposed to external disruption by phages or chemical agents. Endolysis is a key step in phage replication, enabling release of progeny virions.

Mechanism: During infection, a phage’s late genes express endolysin, a peptidoglycan-degrading enzyme. The phage-encoded holin proteins accumulate in the cytoplasmic membrane and form pores, permitting endolysin to access the cell wall. The enzymatic activity weakens the peptidoglycan, and the bacterial cell loses integrity due to osmotic pressure, resulting in lysis and release of new phage particles.

Scope and applications: Endolysins have been studied as therapeutic enzymes, sometimes called enzybiotics, aimed at treating bacterial infections. They are especially effective against Gram-positive bacteria where the peptidoglycan layer is exposed. For Gram-negative bacteria, outer membrane barriers present a challenge, though approaches such as engineering endolysins or using permeabilizing agents show promise. Beyond therapy, endolysis concepts inform phage research, antiseptic coatings, and diagnostic tools that leverage phage-mediated lysis.

Terminology: Endolysis is sometimes used interchangeably with endolysin-mediated lysis, but literature commonly distinguishes the enzyme (endolysin) from the lytic process (lysis). The concept highlights the intracellular origin of the lytic event in phage replication and its potential biotechnological applications.