General Microbiology Lecture 2 Fall 2024 PDF

Department of Microbiology and Immunology General Microbiology and Microbial Genetics (PHM211) Fall 2024 Lecture 2 ▪ Prokaryotic microbes (Bacterial cell structure) References 1. Kathlee...

Department of Microbiology and Immunology General Microbiology and Microbial Genetics (PHM211) Fall 2024 Lecture 2 ▪ Prokaryotic microbes (Bacterial cell structure) References 1. Kathleen P Talaro_ Barry Chess - Foundations in microbiology _ basic principles (2012, McGraw-Hill ) 2. Paul G. Engelkirk, Janet Duben-Engelkirk - Burton’s Microbiology for the Health Sciences (2014, Wolters Kluwer Health) 3. Pommerville, J. C. - Alcamo's Fundamentals of Microbiology (2010, Jones & Bartlett Learning) 4. Michael T. Madigan, John M. Martinko, David Stahl, David P. Clark-Brock Biology of Microorganisms (13th Edition) -Benjamin Cummings (2010) 5. Stuart Hogg-Essential Microbiology-Wiley-Blackwell (2013) 6. Gerard J Tortora_ Berdell R Funke_ Christine L Case-My microbiology place CD-ROM [to accompany] Microbiology_ an introduction, 10th ed. [by] Tortora, Funke, Case-Benjamin Cummings (2010) 7. Joanne Willey, Linda Sherwood, Chris Woolverton-Prescott's Principles of Microbiology -McGraw-Hill Science_Engineering_Math (2008) 2 Lecture Lecture1 Learning 2 OutlineOutcomes ▪ By the end of the lecture, students should be able to demonstrate knowledge of: Prokaryotic microbes A. Bacteria I. Bacterial cell morphology (Size – Shape – Arrangement) II. Bacterial cell structure a. Internal structures 1. Cytoplasm 2. Genetic material 3. Ribosomes 4. Inclusion bodies 5. Endospores b. Cell envelope 1. Cell membrane 3 Lecture Learning1 Learning OutcomesOutcomes Demonstrate a comprehensive understanding of microbial diversity, categorizing microorganisms based on their phenotypic and metabolic characteristics. 4 I. Prokaryotes Which of the following are considered prokaryotic organisms? A. Bacteria B. Protists A and D C. Fungi D. Archaea E. Viruses F. Algae 5 I. Prokaryotes Prokaryotic Microbes A. Bacteria 6 I. Prokaryotic Microbes A. Bacteria Bacterial cell morphology a. Size: ▪ Most bacteria fall within the general dimensions from 0.7-8 µm. ▪ Bacteria are visualized by compound light microscopes under the highest power of magnification (1000X). ▪ Internal structures of bacteria can only be visualized by electron microscope. b. Shape: ▪ It is imparted by the cell wall ▪ The major shapes of bacterial cells include: ▪ Spherical: cocci (sing.: coccus) ▪ Cylindrical: bacilli (sing.: bacillus) ▪ Coma-shaped: vibrios ▪ Spiral-shaped: ▪ rigid spirals; spirilla, (sing.: spirillum) ▪ flexible spirals; spirochetes ▪ Some bacteria are filamentous, star-, rectangular, or square-shaped. 7 I. Prokaryotic Microbes A. Bacteria Bacterial cell morphology c. Arrangement ▪ Often characteristic of certain genera. ▪ Influenced by the pattern of cell division (the number of planes in which a given species divides) and how they remain attached afterwards. Different cell arrangements of cocci Different cell arrangements of bacilli (a) Division in the transverse plane (short axis) or Diplobacilli Streptobacilli Palisades 8 I. Prokaryotic Microbes A. Bacteria Bacterial cell morphology Explain why bacilli are less varied in arrangement than cocci. 9 I. Prokaryotic Microbes A. Bacteria Bacterial cell morphology Pleomorphism ▪ It is The ability of cells of the same bacterial species to exist in a variety of shapes. ▪ Bacteria that exist in a variety of shapes are described as being pleomorphic ▪ Bacteria that maintain a single shape are described as being monomorphic ▪ Causes: 1. Individual variation in cell wall structure caused by nutritional or slight hereditary differences (e.g.; Corynebacterium diphtheria) 2. Lack of cell walls (e.g.; Mycoplasmas) 10  I. Prokaryotic Microbes A. Bacteria Bacterial cell structure a. Cytoplasm I. Internal d. Inclusion bodies ` b. Genetic material e. endospores Cell structures c. Ribosomes Bacterial II. Cell a. Cell membrane ` Envelope b. Cell wall ` a. Appendages (cell extensions) III. External 1. Flagella structures 2. Axial`filaments 3. Fimbriae and Pilli b. Glycocalyx 11 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure Discover the bacterial cell in 3D 12 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 1. Cytoplasm ≠ Eukaryotes It doesn’t contain membrane –bound organelles ▪ The thick, aqueous, semitransparent substance inside the plasma membrane. ▪ Structure: ▪ Water (70-80%) ▪ Proteins (enzymes), carbohydrates, lipids, inorganic ions, and many low molecular weight compounds. ▪ Function: ▪ The cytoplasm is a complex mixture of all the materials required by the cell for its metabolic functions. ▪ The cytoplasm contains: ▪ The nucleoid, and plasmids ▪ Ribosomes ▪ Inclusion bodies 13 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures ≠ Eukaryotes 2. Genetic Material - Not enclosed by nuclear membrane - Single copy a. Bacterial chromosome - No histones ▪ The cell's genetic information ▪ It occupies a well-defined area within the cell called (Nucleoid) but lacks a surrounding nuclear membrane. ▪ Function: ▪ It carries all the information (genes) required for the cell's structures and functions. ▪ Structure: ▪ Circular double-stranded deoxyribonucleic acid (DNA) (sometimes linear). ▪ Single copy per cell (sometimes more than one copy). ▪ Many times, longer than the cell therefore tightly coiled (supercoiled) around special basic protein molecules (not histones) to fit inside the cell. 14 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 2. Genetic Material B. Plasmids ▪ Self-replicating extrachromosomal DNA. ≠ Eukaryotes ▪ Bacterial cell may contain: Plasmids are not found in Eukaryotes ▪ No plasmids ▪ One plasmid ▪ Multiple copies of the same plasmid ▪ More than one type of plasmid (i.e. containing different genes). ▪ It can be passed from cell to cell. ▪ Function: ▪ They may include genes encoding functions that are not essential for life (e.g; toxins production and resistance to antibiotics). ▪ Structure: ▪ Small, circular, double stranded DNA (sometimes 15 linear). I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 16 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 3. Ribosome ≠ Eukaryotes ▪ Function: Smaller than eukaryotic ribosomes (80S) ▪ The site of protein synthesis. ▪ Structure: ▪ Ribosomes consist of protein and a type of RNA called ribosomal RNA (rRNA). ▪ They are characterized by their density expressed in “Svedberg units or S units”. Small subunit ▪ Svedberg units are the units of the “sedimentation Large subunit (30S) coefficient”, a measure of the sedimentation velocity in a (50S) centrifuge; heavier and more compact particles sediment faster when centrifuged and have larger Svedberg numbers. ▪ Ribosomes are composed of two subunit: ▪ A small subunit (30S subunit): has an S value of 30. ▪ A large subunit (50S subunit): has an S value of 50. ▪ Overall, the bacterial ribosome has a density of 70S Prokaryotic ribosome (70S) 17 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure ▪ Some antibiotics work by inhibiting protein synthesis through interaction with small or large ribosomal subunits. ▪ Because of differences in prokaryotic and eukaryotic ribosomes Large subunit Small subunit (50S) (30S) The microbial cell can be killed by the antibiotic while the eukaryotic host cell remains unaffected. Prokaryotic ribosome (70S) 18 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 4. Inclusion bodies ▪ Granules of organic or inorganic material present in the cytoplasm. ▪ Functions: A. Storage: nutrients are stored when they are abundant to use them when the environment is deficient. Nutrients are stored for energy production or as structural building blocks. E.g.; glycogen granules (polymer of glucose) and phosphate granules. B. Some used for detection of earth’s magnetic field (by marine bacteria) for downward orientation into favorable conditions. E.g.; Magnetosome (iron oxide deposits) C. Some provide floating to some aquatic bacteria. E.g; Gas vacuoles (air bags). 19 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures A. Sporulation 5. Endospores Unfavorable conditions (Endo=within, spore=dormant structure) Favorable conditions Vegetative Endospores B. Germination ▪ Endospores are highly durable dormant structures that are cells Inert, resting produced intracellularly by some bacteria such as Bacillus, condition that is Metabolically Clostridium, and Sporosarcina. active and capable of high resistance and growing very long-term ▪ Endospores are the hardest of all life forms that are extremely phase survival. resistant to: ▪ Lack of moisture and essential nutrients. ▪ Heat, harsh chemicals, and radiation. ▪ Because one bacterial cell forms a single endospore that germinates into only one vegetative bacterium, sporulation does not increase the number of cells in bacteria and is for survival not a means of reproduction. ▪ Function: ▪ They function as survival structures and enable the organism to withstand unfavorable growth conditions. 20 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 5. Endospores Structure of endospores: 1. The exosporium: Thin protein covering. 2. A spore coat: Several protein layers (thick) 3. The cortex: Loosely cross-linked peptidoglycan 4. Core: It contains: ▪ Cytoplasmic membrane, cytoplasm, nucleoid, ribosomes, and other cellular essentials. ▪ Large amount of dipicolinic acid which is complexed with Ca ions. ▪ Small acid-soluble DNA-binding proteins (SASPs). SASPs protect the DNA backbone from chemical and enzymatic cleavage and are thus involved in dormant spore's high resistance to UV light. 21 I. Prokaryotic Microbes I. Internal Structures 5. Endospores Life cycle of the spore-forming bacteria (two-phase life cycle) (Sporangium) 22 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 5. Endospores Spores shape and position: 1. Round or oval 2. Terminal, subterminal or central 3. Narrower or wider (bulging) than the width Bulging of the cell spore Because of their resistance, presence in soil and dust and the fact that some are pathogenic, the eradication of spores is of particular importance in some processes: 1. The production of sterile pharmaceutical products 2. Routine hospital cleaning 3. Food preservation: (food spoilage or poisoning). 23 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 5. Endospores Causes of endospores resistance: Resistance to antibiotics Resistance to physical agents (boiling, and disinfectants radiation, drying) 1. Low water content: It provides heat resistance. 1. Impermeability: ▪ Due to the osmotic effect of the cortex and Dipicolinic It provides the chemical and acid-Calcium complexes. enzymatic resistance. Note: Heat destroys cells by inactivating proteins and ▪ Due to the thick, DNA and this process requires a certain amount of water. impermeable outer proteinaceous coat 2. Dipicolinic acid-Calcium complexes intercalate in DNA surrounding the spore (insert between bases) stabilizing DNA against heat denaturation and radiation. 3. SASPs bind tightly to DNA and protect it from potential damage from ultraviolet radiation, desiccation, and dry heat. SASPs= Small acid-soluble DNA-binding proteins 24 4. Metabolic inactivity I. Prokaryotic Microbes A. Bacteria Bacterial cell structure I. Internal Structures 5. Endospores 25 https://youtu.be/NAcowliknPs https://youtu.be/NAcowliknPs  I. Prokaryotic Microbes A. Bacteria Bacterial cell structure a. Cytoplasm I. Internal d. Inclusion bodies ` b. Genetic material e. endospores Cell structures c. Ribosomes Bacterial II. Cell a. Cell membrane ` Envelope b. Cell wall ` a. Appendages (cell extensions) III. External 1. Flagella structures 2. Axial`filaments 3. Fimbriae and Pilli b. Glycocalyx 26  I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope ▪ The cell envelope is the boundary between inside and outside a bacterial cell that is formed of two basic layers: a. The cell membrane b. The cell wall (containing outer membrane in Gram negative bacteria) 27 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Also called: ▪ Plasma membrane ▪ Cytoplasmic membrane ▪ Inner membrane ▪ It is a thin structure lying inside the cell wall and enclosing the cytoplasm of the cell 28 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Structure: Phospholipids bilayer - Proteins Polar heads (hydrophilic) - Phospholipid Bilayer: Phospholipids arranged in two parallel rows. Each phospholipid molecule is composed of: Nonpolar tails (hydrophobic) Polar heads: are hydrophilic (water-loving), soluble in water, and on the outer surfaces. Nonpolar tails: are hydrophobic (water- fearing), insoluble in water, and in the interior. - Proteins: Peripheral proteins: associated with inner or outer Fatty surfaces only. acids Integral proteins (transmembrane proteins): fully extends through the phospholipid bilayer. 29 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane 30 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope ≠ Eukaryotes 1. Cell membrane - No Sterols (except Mycoplasma) Function: - Less rigid than eukaryotic membranes. A. Serve as a selective barrier through which materials enter and exit the cell. - Therefore, plasma membranes have selective permeability (also called semipermeability). Thus, allowing certain molecules and ions to pass through the membrane but others cannot. Large molecules (such as proteins) cannot pass through the plasma membrane ▪ Smaller molecules (such as water, oxygen, carbon dioxide, and some simple sugars) usually pass easily. - The movement of materials across plasma membranes also depends on transporter molecules B. The plasma membranes of bacteria contain enzymes capable of catalyzing the chemical reactions that break down nutrients and produce ATP. 31  I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Movement of materials across the cell membrane A. Passive transport: ▪ Transport along the concentration gradient: from high concentration to low concentration ▪ No energy ▪ Types of passive transport: 1. Simple Diffusion: E.g.; small molecules as O2 and CO2. 2. Facilitated diffusion: ▪ Solutes pass through integral membrane proteins (transporters) that act as channels. E.g.; small inorganic ions. 3. Osmosis: transport of solvents either by diffusion or through integral membrane proteins. E.g.; H2O. 32  I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Movement of materials across the cell membrane A. Passive transport: 33 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Movement of materials across the cell membrane B. Active transport: ▪ Transport of molecules against the concentration gradient: from low concentration to high concentration. ▪ Solutes pass through transporters (as in facilitated diffusion). ▪ It requires energy (ATP). ▪ E.g. ions (for example Na+, K+, H+, Ca2+, and Cl-), amino acids, and simple sugars. 34 I. Prokaryotic Microbes A. Bacteria Bacterial cell structure II. Cell envelope 1. Cell membrane Mesosomes ▪ Inward large irregular folds of the cell membranes. ▪ Function: Mesosomes may be membrane artifacts created during preparing cells for electron microscopy not true cell structures. However, many functions have been proposed for mesosomes: ▪ Guiding the duplicated bacterial chromosomes into the two daughter cells during cell division. ▪ Increasing the surface area of the cell, aiding the cell in cellular respiration (like mitochondrion in eukaryotic cells). Several antimicrobial substances act on the cell membrane making holes in the bilayer, while some detergents and alcohols dissolve the bilayer allowing the cytoplasmic contents to leak out of bacterial cells, resulting in death. 35 Faculty of Pharmacy