Lecture 1 General Microbiology and Immunology Mansoura University PDF

# General Microbiology and Immunology ## Course Information * **Course Title:** General Microbiology and Immunology * **Instructor:** Dr. السيد الشربيني حبيب * **Position:** Professor and Head of Microbiology and Immunology Department * **Department:** Microbiology and Immunology * **College:** Fa...

# General Microbiology and Immunology ## Course Information * **Course Title:** General Microbiology and Immunology * **Instructor:** Dr. السيد الشربيني حبيب * **Position:** Professor and Head of Microbiology and Immunology Department * **Department:** Microbiology and Immunology * **College:** Faculty of Pharmacy * **University:** Mansoura University ## Aim The aim of this course is to: * **Classification of Organisms:** Understand how organisms are classified. * **Differences between Eukaryotes and Prokaryotes:** Distinguish between eukaryotes and prokaryotes. * **Bacterial Nomenclature:** Learn about proper naming conventions for bacteria. * **Bacterial Morphology:** Understand the various shapes of bacteria. * **Bacterial Cell Structure:** Explore the internal components of bacterial cells. ## Microbiology: The Big Picture Microbiology is the study of very small living organisms, often too small to be seen with the naked eye. ## The Three Domain System The three-domain system of life was proposed by Carl Woese. He discovered that there are three domains of life based on: * 16sRNA sequences * Cell membrane lipid structure * Sensitivity to antibiotics The three domains are: * Bacteria * Archaea * Eukarya The three domains of life were further classified into six kingdoms: * Eubacteria * Archaea * Protist * Plant * Fungi * Animal ## Differences Between Prokaryotes and Eukaryotes | Property | Eukaryotic Cells | Prokaryotic Cells | |-----------------|-------------------------------------------------|--------------------------------------------------------| | Size | Large cells (10-100) µm | Small cells (1-10) µm | | Nucleus | True nucleus separated by a nuclear membrane | True nucleus is absent. Instead, nucleotide is present | | Cytoplasm | Present containing many organelles | Present but lacking most organelles | | Cell Division | Miosis | Binary fission | | Sexual Systems | Present | Absent | | DNA | 2-46 chromosome | Only one chromosome | | Ribosome | 80s ribosome, consisting of 60s and 40s subunits | 70s ribosome, consisting of 30s and 50s subunits | | Mitochondria | Present | Absent | | Cell Membrane | Sterols present | Sterols absent except in Mycoplasma | | Cell Wall | Cells have cell walls very rarely, have simple chemical nature | Cell wall is present and is very complex in nature (Muramic acid; teichoic acid) | | Spores | Sexual and asexual reproductive spores | Endospores | | Others | Endoplasmic reticulum, lysosomes, and centromeres present | Absent | | Examples | Fungi | Bacteria | ## Prokaryotic and Eukaryotic Cells * A **eukaryotic** cell consists of a nucleus, nucleolus, mitochondria, ribosomes, and endoplasmic reticulum. * A **prokaryotic** cell consists of a nucleoid, ribosomes, a capsule, a cell membrane, a cell wall, and a flagellum. ## Binomial Nomenclature System of Taxonomic Classification Microorganisms are classified into orders, families, genera, and species based on factors such as: * Morphology * Reproduction * Nutrition * Metabolism * Antigenic structure Only the _genus_ and _species_ are used for classification. * **Example:** _Homo sapiens_, _Felis domestica_, _Escherichia coli_ * **Note:** The *genus* is capitalized, and the *species* is not. Both the genus and species are either underlined or italicized. ## Morphology (Bacterial Cell Size, Shape & Arrangement) Bacteria display a wide diversity of sizes and shapes, referred to as *morphologies*. ### A) Size * Bacterial cells are about 10 times smaller than eukaryotic cells and are typically 0.5–5 micrometers in length. * A few species, like _Thiomargarita namibiensis_, can be up to half a millimeter long and visible to the naked eye. * Among the smallest bacteria are members of the genus _Mycoplasma_, which measure only 0.3 micrometers. ### B) Shape * **Cocci:** Spherical shape * **Bacilli:** Rod-like shape * **Coccobacilli:** Elongated Cocci * **Vibrio:** Rod-shaped bacteria that is slightly curved or comma-shaped. * **Spiral:** Wavy or undulating * **Polymorphic:** Many shapes, can stretch and contract. * **Filamentous Bacteria:** Elongated bacteria to form filaments *Example: Actinobacteria*. * **Branched Filamentous Bacteria:** Filamentous bacteria are often surrounded by a sheath that contains many individual cells. *Example: Nocardia*. ### C) Shape and Arrangement * **Cocci:** * **Diplococci:** Pairs of cocci *Example: Streptococcus pneumoniae*. * **Chains:** Chains of cocci *Example: Streptococcus pyogenes*. * **Clusters:** Cocci are arranged in amorphous sheets or clumps (grape-like structure). *Example: Staphylococcus spp* * **Tetrads:** Four cell cluster *Example: Micrococcus luteus.* * **Cubical:** Eight cell cluster *Example: Sarcina spp.* * **Bacilli:** * **Streptobacilli:** Chains of bacilli *Example: Bacillus anthrax*. * **Palisades:** Arranged vertically (fence-like structure) *Example: Corynebacterium diphtheriae.* * **Scattered:** No special arrangement *Example: Escherichia coli.* ## III- Anatomy (Bacterial Cell Structure) A bacterial cell consists of several structures: * **Capsule** * **Cytoplasm** * **Ribosomes** * **Cell Wall** * **Plasma Membrane** * **Nucleoid** * **Plasmid** * **Flagella** * **Fimbriae** ### Bacterial Cell Structure Diagram The image shows a diagram of a bacterial cell and its components: * The cell is enclosed by a cell wall, which is beneath the outer capsule. * The cytoplasm contains the cell's genetic material, stored within the nucleoid. * Ribosomes are small, granular structures involved in protein synthesis. ### Regions of a Prokaryotic Cell Prokaryotic cells have three regions: * **Cytoplasmic region:** Contains the cell genome (DNA), ribosomes, and inclusions. * **Appendages:** Proteins attached to the cell surface such as flagella and pili. * **Cell envelope:** Consists of the capsule, cell wall, and plasma membrane. ## A- Cytoplasm and Cytoplasmic Components The cytoplasm is the *total of everything inside* of the cytoplasmic membrane. It has a gel-like consistency, but small molecules travel through it rapidly, often only taking a few microseconds to travel from one end of the cell to the other. ### Constituents of the Cytoplasm 1. **Proteins:** Primarily enzymes. Proteins vary in size from 8,000 daltons to greater than 1,000,000 daltons, with the average being 40,000 daltons (40 Kilo daltons). 2. **Ribosomes:** Ribosomes are composed of two complex subunits: * The **50S subunit** contains 23s and 5s rRNA, as well as 31 proteins. * The **30S subunit** contains 16s rRNA and 21 proteins. * The unit of measurement for ribosome size is the Svedberg unit, a measure of the rate of sedimentation during centrifugation. * Ribosomes function as workbenches for protein synthesis. * The two subunits combine during protein synthesis to form a complete 70s ribosome. * A typical bacterium can have up to 15,000 ribosomes. 3. **Storage Granules and Inclusions:** Bacteria exist in a very competitive environment where nutrients are often in short supply. * Some bacteria will store excess *carbon* in the form of polyhydroxyalkanoates or glycogen. * Some microbes store soluble nutrients in vacuoles. * Polyphosphate inclusions are reserves of PO4 and energy. * Sulfur granules are common in bacteria that use hydrogen sulfide as an electron source. * Metachromatic granules are bacterial pigments. * Gas vacuoles. * **Waste Materials:** Bacteria also store waste materials, such as alcohol, lactic acid, and acetic acid. 4. **Bacterial Genomic DNA:** Each bacterial cell contains a large, single, circular chromosome, which stores the cell's genetic information. It is located within the nucleoid, which is not surrounded by a membrane. This chromosome contains the basic genetic information required for survival and the production of daughter cells. 5. **Plasmid DNA:** Plasmids are small circular DNA molecules. They carry extra genes that can be beneficial in specific situations, such as: * Antibiotic resistance * Production of toxins * Synthesis of enzymes They are not essential for viability but can be transferred between bacteria. A single cell can have many different plasmids. ## B- Appendages Appendages are proteins attached to the bacterial cell surface. They can give the cell the ability for: * Motility * Transferring genetic material * Attaching to host tissues ### Types of Appendages 1. **Flagella:** These are the organs of motility. * **Flagellin:** Flagella are composed of a long flagellin protein filament that is connected to a hook and rings that anchor it to the cell wall. * **Gram-positive bacteria:** Have two rings attached to the cytoplasmic membrane. * **Gram-negative bacteria:** Have two additional rings found in the outer membrane (Total - 4 rings). * **Length:** Flagella can be up to 20 μm in length. ### Flagella Image Diagram The image shows a bacterial cell with a flagellum. * The flagellum is a long, thin filament that extends from the cell wall. * The flagellum is connected to a hook and a basal body that is anchored to the cell membrane. ### Arrangements of Flagella * **Monotrichous:** A single polar flagellum *Example: Vibrio cholerae.* * **Lophotrichous:** Several polar flagella located at one pole on the bacteria's surfaces. * **Amphitrichous:** Single flagellum on each of two opposite ends. * **Peritrichious:** Have many flagella covering the entire cell surface. *Example: Escherichia coli.* * **Atrichous:** No flagella. ### Flagella Arrangement Image Diagram The image shows four different flagella arrangements: * **(a):** Monotrichous * **(b):** Amphitrichous * **(c):** Lophotrichous * **(d):** Peritrichious ### Types of Bacterial Motion * **Forward Motion:** Produced by a counterclockwise rotation of the flagella. * **Tumbling Motion:** Produced by clockwise rotation of the flagella. The number and distribution of flagella on the bacterial surface are characteristic of a species and are useful for identifying and classifying bacteria. ### For Example: * **Pseudomonads** are gram-negative rods with **polar monotrichous** flagella, which distinguishes them from **enteric bacteria** such as _Escherichia coli_ which have **peritrichous flagella**. * _V cholerae_ has a **single flagellum** at the pole of the cell (**monotrichous**). Flagella can be sheared from the bacterial cell surface without affecting its viability. This will temporarily render the cell non-motile. The cell will then synthesize new flagella and regain motility. Flagella can also function as antigenic determinants (e.g. The **H antigen** of Gram-negative enteric bacteria). 2. **Pili (Fimbriae):** These hair-like surface appendages are composed of a protein called Pilin. They come in two forms with distinct purposes: * **Sex pili:** These pili are relatively long, but they are often only found in a few numbers (generally 1 to 6). They protrude from the cell surface. * **Function:** Sex pili are involved in *conjugation*, the temporary union of two bacterial cells during which one cell transfers part of its genome to the other. * **Common Pili:** These pili are relatively short and numerous, with an average of 200. They cover the cell surface. * **Function:** Common pili are responsible for attachment to *host cells*, often epithelial cells. They bind with other proteins called *adhesins*. * **Virulence:** Common pili are considered major determinants of *bacterial virulence* because they allow pathogens to colonize tissues and resist attacks from phagocytic white blood cells. ### For Example: * **_Neisseria gonorrhoeae_:** Adheres specifically to human cervical or urethral epithelium with its _fimbriae_. * **Enterotoxigenic strains of _E. coli_:** Adhere to the mucosal epithelium of the intestine with their _fimbriae_. ## References and Interactive Educational Resources 1. **Course notes prepared by course coordinator** 2. Cornelissen, C. N., Fisher, B. D., Harvey, R. A., & Harvey, R. A. (2013). *Lippincott’s illustrated reviews: Microbiology*. 3rd edition, Philadelphia: Lippincott Williams & Wilkins. 3. Abbas, Abul K., Andrew H. Lichtman, and Shiv Pillai. *Basic Immunology E-Book: Functions and Disorders of the Immune System*. Elsevier Health Sciences, 2019 4. **[https://www.ekb.eg](https://www.ekb.eg)** ## Interactive Resources | Title | Link/ QR Code | |-----------------------|---------------------------------------------------------------------| | Bacterial motility | https://youtu.be/Nd49n8YDIlg | | Sodium Potassium Pump | https://youtu.be/7NY6XdPBhxo | | Fluid Mosaic Model | https://youtu.be/QqsfUJcfBc | | Gram staining | https://youtu.be/AZS2wb7pMo4 | | Bacterial replication | https://youtu.be/XlCA-cdvSvU | | Growth curve | https://youtu.be/CfOecDMBrOk | ## Quiz 1. **Prokaryotes are characterized by:** * a. Mesosomes absent. * b. Nucleus absent. * c. Paired chromosomes. * d. Cell wall is composed of cellulose. **Answer:** **(b) Nucleus absent** 2. **Single flagellum on each of two opposite ends are known as:** * a. Lophotrichous. * b. Monotrichous * c. Amphitrichous. * d. Peritrichious. **Answer:** **(c) Amphitrichous** ## Thank You