The characteristics of eukaryotic microorganisms

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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.

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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.

Sample Answer

       

Characteristics of Eukaryotic Microorganisms 🦠

  Eukaryotic microorganisms are a diverse group that includes fungi, protists, and helminths. Their defining characteristic is a eukaryotic cell structure, meaning they have a true nucleus that houses their genetic material, and other membrane-bound organelles like mitochondria, the endoplasmic reticulum, and Golgi apparatus. These microorganisms are generally larger and more complex than prokaryotes. They can be single-celled, like yeast, or multicellular, like some fungi and helminths. Their cell walls, if present, are made of chitin in fungi, or other substances in protists, which is different from the peptidoglycan found in bacteria.

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Life Cycles of Select Eukaryotic Organisms 🔁

  Eukaryotic microorganisms have varied life cycles. For example, the fungus Saccharomyces cerevisiae (baker's yeast) can reproduce both asexually and sexually. Asexually, it uses budding, where a new cell grows from a small bud on the parent cell. Sexually, it can form spores that germinate under favorable conditions. Another example is the protist Plasmodium, the parasite that causes malaria. Its complex life cycle involves both a mosquito and a human host. Within the human, the parasite reproduces asexually in the liver and red blood cells, while sexual reproduction occurs inside the mosquito.

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Defining Acellular and Describing Viruses and Prions 🔬

  Acellular means "not consisting of cells" or "without cells." Viruses and prions are examples of acellular entities.

• • Viruses are obligate intracellular parasites. Their structure consists of a protein coat called a capsid that encloses their genetic material, which can be either DNA or RNA. Some viruses also have an outer lipid membrane called an envelope, which is derived from the host cell. Viruses lack ribosomes, mitochondria, and other cellular machinery, so they cannot replicate on their own.

• Prions are even simpler. They are infectious proteins that lack any genetic material (DNA or RNA). They are misfolded versions of a normal protein found on the surface of cells, particularly in the brain. Prions cause other normal proteins to misfold, leading to a chain reaction that results in neurodegenerative diseases like Creutzfeldt-Jakob disease.