Introduction à la Microbiologie - Chapitre 1

Introduction to Microbiology

• This course covers cytology and cellular physiology.
• The course is taught by Dr. Becheur Mourad ([email protected]) and Dr. Hammadi Soumia ([email protected]).
• The course spans 2024-2025 academic year.

Chapter 1: General Organization of the Cell

• The lecture presents the general organization of a typical cell.
• A diagram/image of a cell with its internal components is included.

Chapter 1: Diversity of Organisms

• The different types of cells, namely prokaryotic cells (bacteria), eukaryotic cells, and viruses are discussed.
• The module highlights the key differences between prokaryotic bacteria and eukaryotic organisms.

Chapter 1: Prokaryotic Cells (Bacteria)

• The nature of prokaryotic cell is explained.
• Prokaryotic cells lack a nucleus and membrane-bound organelles.
• Key microscopic images of bacteria cells are shown.

Comparison of Eubacteria and Archaebacteria

• Eubacteria (bacteria): live in normal conditions, have a peptidoglycan wall, tolerate low salt concentrations
• Archaebacteria: live in extreme conditions, lack a peptidoglycan wall, tolerate high salt concentrations.
• Key differences in temperature, pH, and salt tolerances, as well as compositional differences for their walls, are highlighted.
• Halophiles are extreme lovers (extreme salt lovers).
• Thermophiles are extreme lovers of heat.
• Thermoacidophiles are lovers of both extreme heat and extreme acidity.
• Methanococcus (methane producers) are a type of archaebacteria.

Classification of Eubacteria

• The classification of bacteria follows a hierarchical system. Taxonomy is described with the use of diagrams
• The principle of nomenclature, emphasizing the use of binomial nomenclature (genus and species names), is explained.
• Examples of bacterial classifications, such as Escherichia coli and Streptococcus pneumoniae are given, listing domains, kingdoms, orders, families, genus and species.

Methods of Classification of Eubacteria

• Phenotypic classification (based on size, shape and Gram staining).
• Analytical classification (requiring laboratory analysis or identification specific materials).
• Genotypic classification (using DNA analysis or related techniques to classify).

Bacterial Morpho-functional Specificities

• Bacterial sizes range from 1 to 10 µm and are described.
• Images display different bacterial shapes (cocci, bacilli, vibrios, spirilla).
• Different bacterial grouping modes (isolated, chains and clusters) are shown in images.
• The slide/page shows specific morphologies for different bacteria groups and their diseases.

Bacterial Morpho-functional Specificities: Form and Grouping Modes

• Images of Diplococcus
• Images/examples of Streptococci (in chains)
• Images/examples of Staphylococci (clusters)

Bacterial Morpho-functional Specificities: Examples of Bacteria (Pathogenic & Symbiotic)

• Examples of pathogenic bacteria (e.g., Streptococcus pyogenes, Staphylococcus aureus, Salmonella typhi, Streptococcus pneumoniae, etc.) and their corresponding diseases are listed.
• Specific characteristics of each bacteria discussed.
• Examples of beneficial/symbiotic bacteria (e.g., Lactobacillus, Bifidobacterium longum, Streptococcus thermophilus) and their roles in the human body. Microbiome is introduced.

Bacterial Morpho-functional Specificities: Metabolism

• Aerobic bacteria require oxygen to live.
• Anaerobic bacteria do not require oxygen.
• Facultative anaerobes can use oxygen when present but can also grow without it.

Bacterial Morpho-functional Specificities: Reproduction

• Binary fission is the main mode of bacterial reproduction.
• The stages of binary fission are explained step by step.
• The information is supported with diagrams illustrating the process.
• It is noted that no mitosis or meiosis occur during bacterial reproduction.

Bacterial Ultrastructure: Obligatory Structures

• Sections describe the cell wall, plasma membrane, hyaloplasm and ribosomes.
• The nature and role of each structure, including its composition, are extensively treated with diagrams support.
• These components are common to most types of bacteria.

Bacterial Ultrastructure: Facultative Structures

• This section covers capsule, mesosome, pili, flagellum, plasmids, and spores.
• It details their composition, function (e.g., protection, adhesion, genetic exchange, resistance).
• Examples of bacteria with these structures.

Bacterial Conjugaison

• This process is explained step by step.
• A diagram supports the explanation.
• Explains the importance of conjugaison in genetic exchange between bacteria and in the development of genetic diversity in bacterial populations.
• Emphasizes that conjugal gene transfer is a form of horizontal gene transfer.

Bacterial Flagella

• Explains the composition and function of flagella (motility).
• Explains how these components offer mobility to bacteria.

Symbiotic and Pathogenic Bacteria

• Symbiotic bacteria live in a mutualistic relationship with humans.
• The different locations (i.e., microbiome) of symbiotic and pathogenic bacteria in the human body are outlined
• Characteristics of various pathogenic bacteria and related diseases are detailed.

Bacterial Resistance (Plasmids & Sporulation)

• The process of bacterial resistance through plasmids (carrying antibiotic resistance genes) and sporulation (forming resistant spores) is explained.
• It shows how bacteria can adapt to adverse conditions.
• The mechanism and role of plasmids is introduced.
• Relevant diagrams illustrating the process are presented
• Bacteria resistance to antibiotics is described and related examples are introduced (e.g Clostridium botulinum).

Bacterial Resistance: Sporulation (Detailed steps)

• Steps/mechanism of sporulation are discussed in detail.
• Structure of spore (e.g.: tunica sporale, cortex, paroi sporale, membrane plasmique, cytoplasme, appareils nucléaires) is explained with diagram.
• The conditions for sporulation.

Bacterial Gram Staining

• The history of Gram staining, and the methods, including fixing the smear, crystal violet coloring, iodine mordanting, ethanol/acetone decolorizing, and safranin recoloring.
• Differences between Gram + and Gram - bacteria.
• The structure of bacterial walls (+/-) is related to the staining results in images
• How the staining process yields two types of bacterium reaction and the reason behind is detailed.

Molecular Components of Bacterial Walls (Gram + and Gram -)

• Compositional differences between Gram+ and Gram- cell walls.

Comparison between Eukaryotic and Prokaryotic Cells

• Key distinguishing features of eukaryotic and prokaryotic cells are tabulated.
• Tables are used to compare their sizes, modes of division, types of cells, presence/absence of nucleus and other cell components, and more.