Microbial World: Definition, Explanation and Keynotes

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Microbial World

The organisms which are not visible with the naked eye are simply called microorganisms and the world of these organisms is the microbial world. The microbial world is consisting of microorganisms like bacteria, fungus, and parasites on blood agar as shown above figure. 5 days old culture plate of blood agar has lost its original color and is covered with various organisms-bacterial colonies, fungal growth at the center, and trekking of maggots ( larvae) of a variety of fly species (myia is Greek for fly) within the arthropod order Diptera. Worldwide, the most common flies that cause human infestation are Dermatobia hominis (human botfly) and Cordylobia anthropophaga (tumbu fly).

Explanation of Microbial World

The existence of microorganisms could only be guessed at before the development of the first primitive microscopes in the 17th century by  Antonie Philips van Leeuwenhoek ( 24 October 1632 – 26 August 1723)  and he was a Dutch businessman and scientist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as “the Father of Microbiology”, and one of the first microscopists and microbiologists. Van Leeuwenhoek is best known for his pioneering work in microscopy and for his contributions toward the establishment of microbiology as a scientific discipline. Microorganisms are among the most successful living things. The term microbe, or microorganism, was used extensively because microbes, particularly those relatively few which are pathogens. The term microbe was not defined or even adequately described, but their ‘club’ claims among its members in six groups of microbes were named- bacteria, viruses, protozoans, unicellular algae, fungi, and prions.

Bacterial diseases

Bacteria cause disease by secreting or excreting toxins (as in botulism), by producing toxins internally, which are released when the bacteria disintegrate (as in typhoid), or by inducing sensitivity to their antigenic properties (as in tuberculosis). Other serious bacterial diseases include cholera, diphtheria, bacterial meningitis, tetanus, Lyme disease, gonorrhea, and syphilis.

Viral infections or Diseases 

Respiratory viral diseases

  1. flu
  2. common cold
  3. respiratory syncytial virus infection
  4. adenovirus infection
  5. parainfluenza virus infection
  6. severe acute respiratory syndrome (SARS)

Gastrointestinal viral diseases

  • norovirus infection
  • rotavirus infection
  • some adenovirus infections
  • astrovirus infection

Exanthematous viral disease

  • measles
  • rubella
  • chickenpox/shingles
  • roseola
  • smallpox
  • fifth disease/slapped cheek disease
  • chikungunya virus infection

Hepatic viral diseases

  • hepatitis A
  • hepatitis B
  • hepatitis C
  • hepatitis D
  • hepatitis E

Cutaneous viral diseases

  • warts, including genital warts
  • oral herpes
  • genital herpes
  • molluscum contagiosum

Hemorrhagic viral diseases

  • Ebola
  • Lassa fever
  • dengue fever
  • yellow fever
  • Marburg hemorrhagic fever
  • Crimean-Congo hemorrhagic fever

Neurologic viral diseases

  • polio
  • viral meningitis
  • viral encephalitis
  • rabies

Fungal diseases

  • Candidiasis
  • Cryptococcosis
  • Aspergillosis
  • Coccidioidomycosis (Valley Fever)
  • Histoplasmosis
  • Blastomycosis
  • Pneumocystis pneumonia

Parasitic Diseases 

Ectoparasitic Diseases

  • myiasis
  • pediculosis
  • phthiriasis
  • scabies
  • trombiculosis

Helminthic Diseases 

  • ascariasis
  • cestodiasis
  • clonorchiasis
  • echinococcosis
  • enterobiasis
  • fascioliasis
  • fasciolopsiasis
  • filariasis
  • guinea worm disease
  • heartworm disease
  • heterophyiasis
  • hookworm disease
  • loiasis
  • onchocerciasis
  • paragonimiasis
  • rat lungworm disease (angiostrongyliasis)
  • schistosomiasis
  • strongyloidiasis
  • trichinosis
  • trichuriasis

Protozoan Diseases 

  • amebiasis
  • amebic dysentery
  • babesiosis
  • balantidiosis
  • blackwater fever
  • Chagas disease
  • coccidiosis
  • enterohepatitis
  • giardiasis
  • leishmaniasis
  • malaria
  • sleeping sickness
  • toxoplasmosis
  • trichomoniasis
  • trypanosomiasis

Human Prion Diseases

  1. Creutzfeldt-Jakob Disease (CJD)
  2. Variant Creutzfeldt-Jakob Disease (vCJD)
  3. Gerstmann-Straussler-Scheinker Syndrome
  4. Fatal Familial Insomnia
  5. Kuru


  1.  Worms, biologically known as helminths are frequently included in microbiology even though they are microbes because many species cause infections resembling microbial infections.
  2. Prion is a proteinaceous infectious particle that can replicate itself. It is the smallest among other microbes having a molecular weight of 35–36 kDa.


  1. http://samples.jbpub.com/9780763756895/56895_CH02_027_045.pdf
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6161638/
  3. https://emedicine.medscape.com/article/1491170-
  4. https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek
  5. https://www.britannica.com/science/bacterial-disease
  6. https://www.healthline.com/health/viral-diseases
  7. https://www.niaid.nih.gov/diseases-conditions/fungal-disease-specific-research
  8. https://www.cdc.gov/prions/index.html
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