Virus and Bacteria | Science & Technology for UPSC CSE PDF Download

Introduction

Bacteria

• Bacteria are single-celled microorganisms.
• They exhibit a wide variety of shapes and structural features.
• Bacteria can thrive in diverse environments, including the human body.
• While many bacteria are harmless or even beneficial, some can cause infections in humans and are known as pathogenic bacteria.
• Bacterial infections can lead to various diseases, and antibiotics are often used to treat bacterial infections.

Viruses

• Viruses are even smaller than bacteria and are considered microscopic infectious agents.
• They come in diverse shapes and sizes and can infect a wide range of organisms, including humans.
• Viruses are obligate intracellular parasites, meaning they require a living host cell to replicate and reproduce.
• Once inside a host cell, viruses hijack the cellular machinery to replicate and produce more virus particles.
• Some viruses can damage or destroy host cells during the replication process, which can lead to diseases.
• Vaccines and antiviral medications are used to prevent and treat viral infections.

Viruses

• Viruses are not classified as true living organisms because they lack cellular structures.
• They are characterized by an inert crystalline structure outside a living cell.
• Viruses are obligate parasites, meaning they depend on a host cell to replicate and reproduce, often causing harm or cell death.
• The term "virus" was coined by Louis Pasteur and means "venom" or "poisonous fluid."
• Viruses contain genetic material, which can be either RNA or DNA, but not both simultaneously.
• Viruses that infect plants typically have single-stranded RNA, while those infecting animals may have single or double-stranded RNA or double-stranded DNA.
• Bacteriophages, which infect bacteria, are typically double-stranded DNA viruses.
• Viruses have a protective protein coat called a capsid, composed of smaller subunits known as capsomeres.
• Capsomeres can be arranged in helical or polyhedral geometric forms depending on the virus.

Some examples of viral infections include

• influenza
• common cold
• viral gastroenteritis
• chickenpox
• measles
• viral meningitis
• warts
• human immunodeficiency virus (HIV)
• viral hepatitis
• Zika virus
• West Nile virus
• COVID-19 is another illness caused by a virus. This virus commonly causes:
  • shortness of breath
  • fever
  • dry cough

Bacteria

• Bacteria are single-cell, living organisms capable of independent survival without a host.
• They can thrive in various environments, including surfaces, soil, water, and air.
• Antibiotics are effective in treating bacterial infections by targeting and killing bacteria. However, antibiotics do not work against viruses.
• Some antiviral drugs can help prevent or manage viral infections by interfering with the virus's ability to enter host cells or reproduce.
• Bacteria typically reproduce through a simple process of cell division, where one cell splits into two.
• Bacterial infections can lead to various diseases, such as pneumonia and food poisoning.
• It's essential to note that not all bacteria are harmful; some beneficial bacteria play crucial roles in protecting human health and aiding in various bodily functions.

Some examples of bacterial infections include

• strep throat
• urinary tract infection (UTI)
• bacterial food poisoning
• gonorrhea
• tuberculosis
• bacterial meningitis
• cellulitis
• Lyme disease
• tetanus

Difference between Virus and Bacteria

Viroids

• Viroids are infectious agents that are smaller than viruses, making them one of the simplest known pathogens.
• Unlike viruses, viroids consist solely of a single, free RNA molecule and do not have a protective protein coat.
• The term "viroid" is derived from the combination of "virus" and "RNA" due to their nature as small, infectious RNA molecules.
• Viroids have a low molecular weight, as they are composed solely of RNA.
• Viroids are known to cause diseases in various plants. One notable example is the "potato spindle tuber disease," which is caused by a viroid.

Difference Between DNA & RNA Viruses

• DNA Viruses:
  • Contain DNA as their genetic material.
  • Typically double-stranded.
  • Replicate in the nucleus of host cells.
  • Generally stable.
• RNA Viruses:
  • Contain RNA as their genetic material.
  • Typically single-stranded.
  • Replicate in the cytoplasm of host cells.
  • Generally less stable and have a higher mutation rate than DNA viruses.
• Antigens:
  • Substances recognized by the body as foreign, triggering an immune response.
• Antibodies:
  • Blood proteins produced by the body in response to antigens, aiming to neutralize or eliminate them.

Difference between DNA vs RNA

Difference between Gene & Genome