We have learned about different types of microbes and their benefits to humans. We have also learnt about the various diseases they cause and their repercussions.
Of the many types of microbes, bacteria and viruses cause a majority of the diseases. These can range from mild illness such as the common cold to severe medical conditions such as necrotising fasciitis (also called flesh-eating disease).
However, they are vastly different from each other in terms of physiology, morphology, and anatomy. Therefore, it is essential to learn the difference between virus and bacteria.
Difference Between Virus And Bacteria
One significant difference between virus and bacteria is their size. Generally, bacteria are much larger compared to viruses. Other significant differences are as follows:
|Bacteria have a lipopolysaccharide or Peptidoglycan-based cell wall||The cell wall is absent in viruses. Instead, a capsid (protein coat) is present.|
|Bacteria are generally larger. Size ranges between 900 – 1000nm||Viruses are generally smaller. Size ranges between 30-50nm|
|Bacteria are classified as living organisms||Viruses are neither living nor non-living|
Mode of Reproduction
|Bacteria – Binary fission – A mode of asexual reproduction||Virus – Lytic infection – Hijacks a host’s cellular machinery and produces copies of itself.|
|Most bacteria can reproduce without a host||A virus needs a host to complete its reproductive cycle|
|Present in bacteria||Absent in viruses|
RNA and DNA
|RNA or DNA drift freely in the bacterial cytoplasm||RNA or DNA are enveloped inside a protein coat in viruses|
|Bacterial infections are generally localised (Pneumonia)||Viral infections are usually systemic (Flu)|
|Depends on the type of bacterial infection (incubation period of bacterial pneumonia is 1-2 weeks)||Depends on the type of viral infection (incubation period of rabies is between 20 days to 2 months)|
|Gastritis, food poisoning, ulcers, meningitis, and pneumonia are common bacterial diseases||AIDS, common cold, influenza, and chickenpox are examples of viral diseases|
|Antibiotics are effective for bacterial infections||Antiviral drugs are prescribed for viral infections|
|Vibrio cholerae, Staphylococcus aureus||Hepatitis A virus, HIV, Rhinovirus|
What is Bacteria?
Main article: Bacteria
Bacteria are microscopic, single-celled entities that flourish in diverse environments. Some thrive in the soil; others live deep inside a human gut. Some bacteria are useful to humans, while others are malevolent and cause disease. The bacteria that cause diseases are known as pathogens.
Bacteria are prokaryotes, which means that membrane-bound organelles are absent. Consequently, the nucleus is also absent in bacteria. Instead, a thread-like mass known as the nucleoid contains the cell’s genetic material.
Characteristics Of Bacteria
- Bacteria are single-celled entities. Most of eubacteria and archaeans grow as independent single cells while some bacteria (myxobacteria) living in the soil form multicellular fruiting bodies that are part of their life cycle.
- Bacteria do not possess complex organelles inside the cells. However, they do possess an internal organisation since the DNA is segregated into sites known as a nucleoid, but these nucleoids are not actually divided from the remaining cell through a membrane.
- The plasma membrane is not a feature of bacteria, as seen in other living cells. Specialised folding of the plasma membrane enables the photosynthetic bacteria to carry out light-dependant reactions of photosynthesis which the photosynthetic eukaryotes carry out on the thylakoid membranes inside the chloroplast.
- The bacterial cell contains ribosomes that are spherical units in which proteins assemble from amino acids with the use of data that is encoded in the ribosomal DNA.
Bacteria have a profound impact on the world’s ecology and play a major role in modern medicine and agriculture.
What is a Virus?
Viruses are extremely small entities which contain either RNA or DNA as the genetic material. They are also smaller than most bacteria.
Viruses are not fully acknowledged as living organisms as they cannot survive outside a host. Anatomically, a typical virus is girdled by a protein coat that is enclosed by a membrane made of proteins. In some viruses, this protein coat is covered by a lipid membrane called the viral envelope.
Characteristics Of Virus
- Viruses reproduce at a tremendous pace but only inside the cells of the living hosts. Furthermore, most viruses have the capability to mutate.
- Viruses lack cellular organelles and cytoplasm
- Most of the viruses contain RNA or DNA, but not both.
- They fail to perform metabolic activities.
- They make use of the metabolic machinery of the host cells. Viruses cannot grow and divide. They produce and assemble new viral components inside the infected host cell.
Main article: Viruses
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Frequently Asked Questions
Q.1. Why are viruses not affected by antibiotics?
A.1. The property of antibiotics is to target certain proteins, or cellular structures present exclusively in the bacteria.
For instance, antibiotics usually target a bacteria’s cell wall, metabolic pathways, DNA gyrase, ribosomes, or topoisomerase. But since these proteins or structures are absent in viruses, antibiotics are useless. In other words, antibiotics operate on the basis of selective toxicity.
Q.2. Why are viruses known as obligate parasites?
A.2. Virus particles are inert outside cells. Therefore, they need to highjack the cellular machinery of their hosts for vital functions.
Q.3. List five diseases caused by viruses.
A.3. Smallpox, Ebola, Hepatitis, Herpes, AIDS
Q.4. Write any five applications of bacteria.
A.4. The applications of bacteria are as follows:
- Bacteria is extensively used in the fermentation process, such as baking and brewing.
- The Lactobacillus bacteria are known to form curd from milk.
- Bacteria are used in the chemical manufacturing of ethanol, organic acids, enzymes, etc
- They are used in the production of pharmaceuticals.
- Most importantly, certain bacteria such as Rhizobium are useful for atmospheric nitrogen fixation.
Q.5. Which bacteria are resistant to antibiotics?
A.5. Usually, bacteria do not resist antibiotics, but some bacteria such as the golden staph or the Staphylococcus and the Neisseria gonorrhoeae have developed a resistance to the antibiotic, benzylpenicillin.