Cytologie et Physiologie cellulaire - Chapitre I

Module de Cytologie et Physiologie cellulaire

• Enseignants: Dr. Becheur Mourad ([email protected]) and Dr. Hammadi Soumia ([email protected])
• Academic Year: 2024-2025
• Course Objectives:
  • Define the bacterial cell
  • Describe the morpho-functional specificities of bacterial cells (including shapes, sizes, grouping, reproduction)
  • Describe essential and optional ultrastructural components (wall, plasma membrane, genome, ribosomes, capsule, mesosome, plasmid, cytoplasmic inclusions, pili, flagella)
  • Provide examples of symbiotic and pathogenic bacteria (Escherichia Coli, streptococci, staphylococci, salmonella)
  • Explain bacterial resistance mechanisms (plasmids, sporulation)
  • Describe the Gram staining procedure and its principles.
  • Identify the molecular components of Gram+ and Gram- bacterial walls.
  • Highlight the distinguishing criteria between animal eukaryotic and bacterial prokaryotic cells

Chapitre I : Organisation générale de la cellule

• This chapter focuses on the general organization of a cell. (Visual aid of a typical cell structure is used).

Diversité des organismes

• 1-1: La cellule eucaryote
• 1-2: La cellule procaryote (bactérienne)
• 1-3: Les virus

I-2 La Cellule bactérienne

• Images of different bacterial forms are included in the slides.

Rappel

• Diagram illustrating the three domains of life (Bacteria, Archaea, Eukarya) is presented and the common ancestor is displayed.

Course Objectives (page 7)

• Further details on the learning objectives are provided, including specifics about bacterial cells, their structures and functions.

1- Définition des procaryotes

• Prokaryotes are primitive unicellular organisms lacking a nucleus. Their genetic material floats in the cytoplasm. Also, they lack membrane-bound organelles.

2- Comparaison entre les Eubactéries et les Archaebactéries

• Eubacteria (Bacteria): Normal living conditions: Normal temperature, neutral pH, low salinity, and peptidoglycan cell wall composition.
• Archaebacteria (Archea): Extreme living conditions: High or low temperature, acidic or basic pH, high salinity, and variable cell wall composition.
• More detailed comparisons: Gram-positive/Gram-negative bacteria and their cell walls, spore formation, presence of histone in the chromosome.

3- Nomenclature et classification des Eubactéries

• Detailed classification system: Domain, Kingdom, Phylum/Division, Class, Order, Family, Genus, Species (e.g., Escherichia coli). The importance of binomial nomenclature (using Latin names) is explained. Actual examples like Escherichia coli and Streptococcus pneumoniae are included in various classifications.

3:1 Classification (Ex: les Animaux)

• This section illustrates a hierarchical system exemplifying the classification of organisms, including an example with the Felis genus.

3:2 Nomenclature et classification des Eubactéries

• A hierarchical classification diagram of Eubacteria is shown with examples like Escherichia coli.

3:2 Nomenclature et classification des Eubactéries: Méthodes de classification

• Phenotypical Classification: Uses observable characteristics (size, shape, Gram stain)
• Analytical Classification: Needs lab equipment and specific materials for analysis (lipids, proteins, enzymes)
• Genotypical Classification: Uses DNA analysis to identify species and family

4- Spécificités morpho-fonctionnelles des bactéries

• 4-1 Taille: Bacterial sizes are compared to viral particles, animal and plant cells. (1 μm to 10 μm)
• 4-2 Forme et mode de groupement: Different bacterial shapes (cocci, bacilli, vibrios, spirochaetes) and grouping patterns (single, pairs, chains, clusters).
• 4-3 Métabolisme: Bacteria are classified into aerobes (require oxygen), anaerobes (do not require oxygen), and facultative anaerobes (can survive with or without oxygen). Examples: Mycobacterium Tuberculosis (aerobic).
• 4-4 Mode de reproduction: Asexual reproduction by binary fission is discussed (steps illustrated).

5- Ultrastructure des bactéries : Structures obligatoires et facultatives

• Obligatory structures: Essential for bacteria: Cell wall, plasma membrane, cytoplasm, ribosomes, nucleoid (circular chromosome).
• Optional structures: Present in some but not all bacteria: Capsule, mesosome, pili, plasmids, flagella. (Illustrated diagrams included, highlighting both types of structures).

5-1 Structures obligatoires (in detail):

• a- Paroi: Rigid structure for shape and protection, primarily composed of peptidoglycan.
• b- Membrane plasmique: Lipoprotein structure; vital for nutrient transport and energy production.
• c- Hyaloplasme: Fluid cytoplasm, containing genetic material, ribosomes and other components.
• d- Chromosome bactérien: Single circular chromosome carrying the bacterium's genetic information.
• e- Ribosomes: Involved in protein synthesis; different in prokaryotes compared to eukaryotes (70S). Detailed diagram comparing 70S and 80S ribosomes are included.

5-2 Structures facultatives (in detail):

• a- Capsule: Polysaccharide layer offering protection and adherence.
• b- Mésosome: Invaginations of the cell membrane, usually in aerobic bacteria, playing a role in DNA replication and respiration. (Note: there is some debate on whether it’s a functional organelle)
• c- Pili: Protein filaments helping with attachment and conjugation.
• d- Plasmides: Extra-chromosomal DNA fragments conferring antibiotic resistance or other useful traits.
• e- Flagelle: Used for bacterial motility, composed of flagellin protein.

6- Bactéries symbiotiques et bactéries pathogènes

• Symbiotic Bacteria: Living in association with another organism; both benefit. Examples of microbiome (gut, skin) .
• Pathogenic Bacteria: Capable of causing disease in the host. Examples of pathogenic bacteria (Staphylococcus aureus, Streptococcus spp., Salmonella).

7- Résistance bactérienne

• Resistance mechanisms involving plasmids (carrying antibiotic resistance genes)
• Sporulation (forming resistant endospores to adverse conditions)

8- Coloration de Gram

• Principles of Gram stain (steps to identify Gram-positive/Gram-negative bacteria based on cell wall structure. Diagrams illustrating the Gram-positive and Gram-negative structures.

9- Les composants moléculaires des parois des bactéries Gram+ et Gram-

• Comparison table detailing differences (thickness, peptidoglycan, teichoic acids).

10- Comparaison entre la cellule eucaryote et la cellule procaryote (bactérienne)

• Comparison table contrasting both cell types.

Ce quiz couvre les concepts fondamentaux de la cytologie et de la physiologie cellulaire, avec une attention particulière portée aux cellules bactériennes. Il examine les spécificités morpho-fonctionnelles des cellules bactériennes, ainsi que des exemples de bactéries symbiotiques et pathogènes. Testez vos connaissances sur les mécanismes de résistance bactérienne et la coloration de Gram.