The key difference between eclipse and latent period is that eclipse period is the time of synthesizing phage proteins and nucleic acids inside the host cell, while the latent period is the time between injection of the viral genome into the cell and host cell lysis.
A bacteriophage (phage) is an obligate intracellular virus particle that infects and propagates within a specific bacterium. These are also known as bacteria eaters since they act as bactericidal agents. Head and tail complex shape is the most common shape shown by bacteriophages. They infect the host bacteria in order to reproduce. At the beginning of the infection, they attach tightly to the bacterial cell wall using their surface receptors and inject their genetic material into the host cell. Then their infection can occur via two cycles: lytic and lysogenic cycle.
In the lytic cycle, bacteriophages infect bacteria and rapidly kill the host bacterial cell by lysis. In the lysogenic cycle, viral genetic material integrates with bacterial genome or plasmids and exists within the host cell for many generations without killing the host bacterium. Infection process follows different periods as the latent period, eclipse period, rise period, etc.
CONTENTS
1. Overview and Key Difference
2. What is Eclipse Period
3. What is Latent Period
4. Similarities Between Eclipse and Latent Period
5. Side by Side Comparison – Eclipse vs Latent Period in Tabular Form
6. Summary
What is Eclipse Period?
Eclipse period is the time of bacteriophage growth which starts at the beginning of the latent period and ends at the first appearance of the new intracellular viral progeny inside the host cell. During the eclipse period, new nucleic acids and phage proteins are synthesized.
Figure 01: Lytic Cycle
The eclipse period is nested within the latent period. In fact, the eclipse phase is the first stage of infection, and it starts in the first few minutes after infection. Therefore, during the eclipse period, new viral components are synthesized and start assembling. Mature phage progeny appears at the end of the eclipse period.
What is Latent Period?
In a bacteriophage growth, the latent period is the time between injection or uptake of the viral genome into the host cell to release of new viral progeny by host cell lysis. Therefore, the latent period begins with the viral attachment with the bacterial cell wall. Then it extends via different stages and terminates at the point of phage-progeny release by lysis of the host bacterial cell. In simple words, the latent period is the timing of phage induced host cell lysis. Eclipse period lies within the latent period. During the latent period, the host cell is under the control of the phage protein complex.
Figure 02: Latent Period
The specific processes that occur during the latent period are;
- translocation of the viral nucleic acid into the bacterial cytoplasm from the periplasm
- replication of the viral nucleic acids
- expression of viral proteins
- packaging of viral particles
- maturation of viral particles
- disruption of the host cell membrane, and
- release of viral progeny.
The latent period varies among the different viral-host systems. The latent period of T4 and E. coli is 20 minutes while it is 50 minutes for λ and E. coli. Likewise, the latent period differs among phage systems, and it is influenced by the host physiology as well.
What are the Similarities Between Eclipse and Latent Period?
- Eclipse and latent periods are two durations of the phage lytic cycle.
- In fact, the eclipse period is a part of the latent period.
- Both periods are influenced by host physiology.
What is the Difference Between Eclipse and Latent Period?
Eclipse period is a part of the latent period in which new phage proteins and nucleic acids are synthesized within the host cell. On the other hand, the latent period is the time between the injection of the viral genome to host cell and host cell lysis in order to release new viral progeny. So, this is the key difference between latent and eclipse period. Moreover, in comparison, the eclipse period runs for a short time. But, in contrast, the latent period runs comparatively a longer time. Thus, this is also a significant difference between latent and eclipse period.
Furthermore, in the eclipse period, synthesis of new nucleic acid and phage proteins takes place. In latent period, translocation of the viral nucleic acid into the bacterial cytoplasm from the periplasm, replication of the viral nucleic acids, expression of viral proteins, packaging of viral particles, maturation of viral particles, disruption of the host cell membrane and release of viral progeny take place.
Summary – Eclipse vs Latent Period
A bacteriophage is a virus which infects and replicates inside bacteria. Latent period and eclipse period are two phases of bacteriophage growth. During the eclipse period, synthesis of new nucleic acid and phage proteins takes place. Eclipse phase is nested within the latent period. Therefore, the latent period is the time period that begins with the entry of the phage genome into the host cell and terminates at the host cell lysis. So, this summarizes the difference between eclipse and latent period.
Reference:
1. “Microbiology.” Lumen, Available here.
2. “Eclipse Period (Time between the Viral Adsorption and the First Appearance of the Progeny).” Eclipse Period (Time between the Viral Adsorp – Bacteriophage – BNID 111585, Available here.
Image Courtesy:
1. “Concept of incubation period” By Patilsaurabhr – Own work (CC0) via Commons Wikimedia
2. “Lytic Cycle” By xxoverflowed (CC BY 2.0) via Flickr