Diversity of microorganisms — A/L Biology

What must I remember about Diversity of microorganisms?

• Microorganisms comprise diverse microscopic cellular (bacteria, archaea, fungi, protozoa, microalgae) and acellular biological entities (viruses, viroids, prions).
• Bacterial morphology: Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral), and Vibrios (comma-shaped); Gram staining differentiates Gram-positive (thick peptidoglycan, purple) from Gram-negative (thin peptidoglycan with outer lipopolysaccharide membrane, pink).
• Viruses are obligate intracellular acellular parasites: Consist of a genetic core (DNA or RNA, single- or double-stranded) surrounded by a protein coat (capsid), and occasionally an outer lipid envelope.
• Fungal characteristics: Eukaryotic, heterotrophic (saprophytic or parasitic), cell walls composed of chitin; unicellular (yeasts) or filamentous (molds with hyphae forming mycelium).
• Acellular sub-viral agents: Viroids (short, infectious naked circular single-stranded RNA molecules causing plant diseases) and Prions (infectious misfolded proteins causing transmissible spongiform encephalopathies like BSE and CJD).

Test yourself (1 minute)

1. Gram stain protocol sequence

   Crystal violet (primary stain) ⟶ Iodine (mordant) ⟶ Alcohol/acetone (decolorizer) ⟶ Safranin (counterstain).

2. Viral replication cycles

   Lytic cycle results in host cell lysis and release of new virions; Lysogenic cycle involves integration of viral DNA into the host bacterial genome as a latent prophage.

3. Prion resilience

   Prions are extraordinarily resistant to heat, radiation, and standard chemical disinfectants because they lack nucleic acids and are already stably misfolded.

Practise Diversity of microorganisms questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 9

What should I study first?

What comes next?

Next in the syllabus

Where does Diversity of microorganisms fit in the syllabus?

Year 1 · Term 3