Microbiology · MU Sofia

4 – Bacterial Ultrastructure: Contrasting Prokaryotic and Eukaryotic Cells and

Contrasts prokaryotic and eukaryotic cells through a comparison table covering size, nucleus, organelles, chromosomes, cell wall, ribosomes, division, flagella and membrane sterols. It then walks through the bacterial cell's essential structures, such as the cytoplasmic membrane, peptidoglycan cell wall, circular chromosome and 70S ribosomes, before describing non-essential parts like flagellar arrangements, pili, plasmids, capsules and spores.

Inside: 3 sections · 2 labelled pictures · 1 table · 15 flashcards · 3 min

Topic 4 of 113 in the MU Sofia syllabus for Microbiology (Medicine, Year 3). The free AceMed note covers it in 3 sections, about 266 words (3 min of reading), with 15 flashcards.

In this note

  1. 4 – Bacterial Ultrastructure: Contrasting Prokaryotic and Eukaryotic Cells and
  2. CYTOPLASMIC STRUCTURES OF A BACTERIAL CELL
  3. Bacterial Ultrastructure - Cell Wall, Structure and

4 – Bacterial Ultrastructure: Contrasting Prokaryotic and Eukaryotic Cells and

The fundamental distinction between prokaryotes (bacteria and archaea) and eukaryotes (fungi, protozoa, plants, and animals) lies in the organization of their genetic material and the presence or absence of membrane-bound organelles.

CYTOPLASMIC STRUCTURES OF A BACTERIAL CELL

Essential Organelles:

Cytoplasmic Membrane: A phospholipid bilayer that encloses the cytoplasm and controls the passage of substances into and out of the cell.

Cell Wall: A rigid structure that surrounds the cytoplasmic membrane, providing protection and shape to the bacterial cell.

(Composed of peptidoglycan, a polymer of sugars (NAG and NAM) and amino acids. Structure differs between Gram-positive and Gram-negative bacteria, leading to variations in staining properties and susceptibility to antibiotics.)

Chromosome: A single, circular, double-stranded DNA molecule located in the nucleoid region.

Ribosomes: Sites of protein synthesis.(Composed of RNA and protein, forming a 70S ribosome (50S + 30S subunits).)

Non-Essential Organelles:

Flagella: Long, whip-like appendages that provide motility.(Composed of the protein flagellin)

Arrangement varies (monotrichous, lophotrichous, amphitrichous, peritrichous) aiding in bacterial identification.

Pili (Fimbriae): Shorter, thinner, and more numerous than flagella; composed of the protein pilin.

Ordinary Pili: Mediate adherence to host cells, crucial for colonization and infection.

Sex Pili: Facilitate the transfer of genetic material (plasmids) between bacteria during conjugation.

Inclusion Bodies: Nuclear or cytoplasmic aggregates of stainable substances, representing sites of viral multiplication or acting as storage sites (e.g., volutin granules store phosphate).

Plasmids: Extrachromosomal, circular DNA molecules that replicate independently of the chromosome.

Capsule (Glycocalyx): A polysaccharide or polypeptide layer surrounding some bacteria.

  • Functions: Protection, Adherence to host tissues, Protection from desiccation (drying out).

Spores: Highly resistant, dormant structures produced by certain Gram-positive bacteria (e.g., Bacillus and Clostridium) under unfavorable conditions.

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