Bacteriophages (abbreviated as phages) are viruses that infect microorganisms such as bacteria, fungi, algae, actinomycetes, and spirochetes. These viruses are non-toxic and harmless. They are an incredibly massive biological entity in nature and can be found in almost any environment where bacteria exist. Phages exhibit extremely high diversity and play vital roles in ecosystems, including regulating bacterial populations and promoting horizontal gene transfer.
Phages are typically composed of a protein coat (called a capsid) and internal genetic material, which can be either DNA or RNA. Phages reproduce by infecting bacteria; they utilize the metabolic machinery of the host bacteria to synthesize their own components and assemble into new phage particles.
Phages possess a high degree of host specificity, meaning they can generally infect only specific bacterial species or strains.
Based on their life cycles, phages can be classified into two categories: lytic phages and lysogenic phages:
- Lytic Phages: These phages invade bacterial cells, replicate their own genetic material, and ultimately cause the bacterial cell to burst (lysis), releasing new phage particles.
- Lysogenic Phages: After invading bacteria, the genetic material of these phages integrates into the bacterial genome. Instead of causing immediate bacterial death, they remain latent within the bacterial cell. They can sometimes be activated by certain stimuli to transition into the lytic cycle.
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