Skip to main content

Factors affecting to occur lysogenic to lytic cycle


The term “lysogenic” implies that prophages are capable of giving rise to active phages that lyse their host cells. This occurs when the viral genome exits the bacterial chromosome and initiates the lytic cycle. The triggers for this switch-over are usually environmental factors such as mutagens (e.g. radiation and presence of certain chemicals)
It depends on a few factors, such as how many phages infected the cell, whether or not the cell is in good growth conditions, and so on.
If the cell is in stress or has low amounts of nutrients, the lysogenic pathway is typically activated.
The underlying mechanism has to do with a protein cascade involving either the cro or cI protein that is encoded by the virus.
The cI protein is a repressor, and it will prevent the lytic genes from being transcribed. By default the virus will transcribe the lytic genes, so they must be repressed for lysogeny to occur.

Similarly, cro is also a transcriptional repressor.
The two proteins work in opposition to each other. cro binds to an operator, oR3, that is involved in repressing cI, which may prevent cI from being expressed and thus preventing it from repressing lytic genes (however the importance of this is debatable because if you replace oR3, the cell can apparently still lyse).
There are numerous other proteins, such as N and Q, that are involved. The N protein has to be transcribed by the polymerase ‘anti-terminating’, or reading through a termination signal. This will happen more frequently when the protein RNase III is present at high concentrations.
The N protein is a lytic regulator. Thus, when there are high amounts of RNase III there will be more N expressed which leads to the lytic cycle. RNase III is not a viral protein. It is a host protein and the host expresses more of it when nutrients are abundant. This is how the virus is able to ‘sense’ if nutrients are high enough to enter the lytic cycle.


Popular posts from this blog

Analysis of A Temporary Matter by Jhumpa Lahiri

A Temporary Matter A Temporary Matter is a story about grief and the secrets people keep from one another. Husband and wife Shukumar and Shoba are reeling from the loss of their child six months earlier. They avoid each other and their friends, Shoba filling her time with work and Shukumar procrastinating in finishing his dissertation. A deus-ex-machina in the form of systematic power outages allows for intimacy between the couple not achieved since the death of their son. The importance of communication within a marriage is a prevalent theme in  Interpreter of Maladies . Here the sorrow of the lost child causes a communication breakdown in the relationship of Shukumar and Shoba. This silence between them eventually destroys them because, in their grief, Shukumar and Shoba grow to become different people. Since they no longer share experiences, the couple grows apart. Their final secrets are painful ones – Shoba intends to move out and Shukumar violates the wishes of his

Blood Buffer System

Buffer A buffer is an aqueous solution that resists changes in pH upon the addition of an acid or a base . Also, adding water to a buffer or allowing water to evaporate from the buffer does not change the pH of a buffer significantly. Buffers basically constituent a pair of a weak acid and its conjugate base, or a pair of a weak base and its conjugate acid. Blood buffer The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H 2 CO 3 ), bicarbonate ion (HCO3-), and carbon dioxide (CO 2 ) in order to maintain pH in the blood and duodenum , among other tissues, to support proper metabolic function. Catalyzed by carbonic anhydrase , carbon dioxide (CO 2 ) reacts with water (H 2 O) to form carbonic acid (H 2 CO 3 ), which in turn rapidly dissociates to form a bicarbonate ion (HCO3-) and a hydrogen ion (H + ) as shown in the following reaction. C O 2 + H 2 O ⇄ H 2 C O 3 ⇄ H C O 3 − + H + {\displaystyle {\rm {CO_

Analysis of The Treatment of Bibi Haldar by Jhumpa lahiri

The Treatment Of Bibi Haldar Bibi Haldar is a 29-year-old woman who suffers from a disease that no doctor, priest or therapist could quite understand and therefore each of them offered differing 'cures'. Bibi was infamous for her illness, and everyone knew of her suffering. ''She was not pretty. Her upper lip was thin, her teeth too small. Her gums protruded when she spoke.” All Bibi wants is to live life like any other normal girl: get married, have children and be loved. Unfortunately, her illness precludes her from achieving the desired normalcy. As the story unfolds, Bibi eventually finds her 'cure', not through any medical prescription but in a way anyone could ever have imagined. Jhumpa Lahiri Nilanjana Sudeshna "Jhumpa" Lahiri was born in London and brought up in South Kingstown, Rhode Island. Brought up in America by a mother who wanted to raise her children to be Indian, she learned about her Bengali heritage from an early age