The characteristics of eukaryotic microorganisms

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Defining Viral Infections 🦠

 

• Acute infection: An infection characterized by a rapid onset, followed by a short duration. The host immune system typically clears the virus. Example: The common cold caused by a rhinovirus.
• Latent infection: The virus remains dormant in the host's cells after the initial infection, without causing symptoms. It can be reactivated later. Example: Herpes simplex virus (HSV), which causes cold sores, can lie dormant in nerve cells.
• Chronic infection: The virus is not cleared by the immune system and remains in the body for a long period, often years. Example: Hepatitis C virus, which can lead to long-term liver inflammation and damage.
• Viral oncogenesis: The process by which a virus causes cancer. Some viruses can insert their genetic material into a host cell's genome, disrupting cell cycle regulation and leading to uncontrolled cell growth. Example: Human papillomavirus (HPV) is a well-known cause of cervical cancer.

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Bacteriophage vs. Animal Virus Life Cycles 🔄

  Both bacteriophages (viruses that infect bacteria) and animal viruses are obligate intracellular parasites, but their life cycles differ significantly.

• A bacteriophage injects its genetic material into a host bacterium, leaving the capsid outside. The viral genes then hijack the bacterial machinery to produce new phages, which eventually lyse (burst) the cell to be released. This is known as the lytic cycle.
• An animal virus enters a host cell via endocytosis or membrane fusion. The entire virus enters the cell, and the capsid is then uncoated to release the genetic material. The virus uses the human cell's ribosomes to synthesize viral proteins, its endoplasmic reticulum and Golgi apparatus for assembly and modification, and its nucleus to replicate its genetic material (for DNA viruses).

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Viral Growth Requirements vs. Bacteria 🦠➡️🦠

  Viruses have a very specific growth requirement: they must have a living host cell. They are obligate intracellular parasites, meaning they cannot replicate outside of a host. This is a fundamental difference from bacteria, which are living organisms that can grow and replicate on their own on an appropriate growth medium. Bacteria have their own cellular machinery to produce energy and synthesize proteins, whereas viruses are entirely dependent on their host for these processes. Viruses are essentially just genetic information in a protein package, a stark contrast to a self-sufficient bacterial cell.