Microbiology Textbook - Chapter 3 PDF

CHAPTER 3 Cell Structure and Function  Characteristics of Life  Growth  Increase in size  Reproduction  Increase in number (divides)  Responsiveness  React to environmental stimuli  Metabolism  Controlled chemical reactions  Cellular Structur...

CHAPTER 3 Cell Structure and Function  Characteristics of Life  Growth  Increase in size  Reproduction  Increase in number (divides)  Responsiveness  React to environmental stimuli  Metabolism  Controlled chemical reactions  Cellular Structure  M-bound structure capable of all functions above Characteristics of Life  Figure 3.2 Typical prokaryotic cell Prokaryotic Cells  Figure 3.3 Typical eukaryotic cell Eukaryotic Cells  Figure 3.4 Approximate size of various types of cells Eukaryotic Cells  Bacterial Cells - Glycocalyces  Capsule  Composed of polysaccharides  Firmly attached to cell surface  Protection  i.e. Streptococcus pneumonia Figure 3.5 Glycocalyces Bacterial Cells – External Structures  Bacterial Cells - Glycocalyces  Slime layer  Loosely attached to cell surface  Sticky layer allows prokaryotes to attach to surfaces  i.e. Pseudomonas spp. Figure 3.5 Glycocalyces Bacterial Cells – External Structures  Bacterial Cells - Flagella  Responsible for bacterial motility, if present  Composed of filament, hook, and basal body * Basal body anchors the filament and hook to cell wall Bacterial Cells – External Structures  Figure 3.6 Proximal structure of bacterial flagella Bacterial Cells – External Structures  Figure 3.8 Axial filament (Spirochetes) - Endoflagella Bacterial Cells – External Structures  Bacterial Cells - Flagella  Rotation propels bacterium through environment  Bacteria move in response to stimuli (taxis)  Runs (ccw)  Tumbles (cw) Figure 3.9 Motion of a peritrichous bacterium Bacterial Cells – External Structures  Fimbriae  Sticky, bristle like projections; shorter than flagella  Used by bacteria to adhere to one another and to substances in environment Figure 3.11 Biofilms Figure 3.10 Fimbriae Bacterial Cells – External Structures  Pili  Special type of fimbriae; longer than fimbriae  Conjugation pili  Bacteria typically have only one or a few conjugation pili per cell  Transfer DNA (plasmid) from one cell to another via conjugation Figure 3.12 Conjugation Pilus Bacterial Cells – External Structures  Bacterial Cell Walls  Provide characteristic shapes of bacterial cells  Protect cell from osmotic forces  Assist some cells in attaching to other cells  Antibiotics may disrupt the CW Figure 3.13 Bacterial shapes and arrangements Bacterial Cells  Bacterial Cell Walls  Composed of peptidoglycan  Two basic types of bacteria based on their cell walls:  Gram-positive – thick layer of peptidoglycan  Gram-negative – thin layer of peptidoglycan Bacterial Cells  Bacterial Cell Walls  Peptidoglycan  Millions of NAG and NAM Bacterial Cells  Gram-Positive Bacteria  Relatively thick layer of peptidoglycan  Also have  Teichoic acids  Lipoteichoic acids  Appear purple following Gram staining procedure Figure 3.16a Bacterial Cells  Gram-variable Bacteria  Mycobacterium  Causative agent of leprosy, tuberculosis  Have up to 60% mycolic acid (waxy lipid) in their walls  Helps prevent drying out Bacterial Cells  Gram-Negative Bacteria  Thin layer of peptidoglycan  Bilayer membrane outside the peptidoglycan:  Phospholipids, proteins, lipopolysaccharide (LPS) * Lipid A portion of LPS can cause fever, vasodilation, inflammation, shock, and blood clotting  May impede the treatment of disease  Appear pink following Gram staining procedure Bacterial Cells  Figure 3.16b Cell wall of Gram-negative bacteria Bacterial Cells  Bacteria Without Cell Walls  A few bacteria lack cell walls:  Ureaplasmas * Cause urogenital infections  Mycoplasmas * Cause atypical ‘walking’ pneumonia * Smallest of the bacteria Scanning electron micrograph of M. pneumoniae cells. https://cmr.asm.org/content/17/ 4/697/figures-only Bacterial Cells  Bacterial Cytoplasmic Membranes  Arranged as a bilayer  Phospholipids and hopanoids (stabilize M)  Integral and peripheral proteins Figure 3.1 Bacterial Cell Membranes  Bacterial Cytoplasmic Membranes  Active processes:  Active transport * ATP-dependent carrier proteins use energy to transport substances across the M into the cell * Na+, K+, Ca2+, Cl-, H+ Figure 3.22 Prokaryotic Cell Membranes  Bacterial Cytoplasmic Membranes  Active processes:  Group translocation * Substance is chemically modified during transport * Glucose, mannose, fructose Figure 3.23 Prokaryotic Cell Membranes Prokaryotic Cell Membranes  Cytoplasm of Bacteria  Cytosol  Contains cell’s DNA in region called the nucleoid  Liquid portion of cytoplasm  Mostly water  Inclusions  May include reserve deposits Figure 3.24 Granules of PHB of chemicals, nutrients (polyhydroxylbutyrate) in the bacterium Azotobacter chroococcum Bacterial Cells  Endospores  Unique structures produced by some bacteria  Defensive strategy against unfavorable conditions  Resistant to extreme conditions such as heat, radiation, chemicals  Bacillus anthracis  Clostridium spp Bacterial Cells  Clinically Important Endospore-forming Bacteria  Medically relevant species that make endospores are in the Bacillus and Clostridium genera  Examples: * Clostridium tetani * Clostridium botulinum * Clostridium perfringens * Clostridium difficile * Bacillus anthracis  Endospores survive for extended periods on surfaces, even in healthcare facilities Bacterial Cells  Figure 3.25 Formation of an endospore Bacterial Cells  Components of Bacterial Cells  Ribosomes  Sites of protein synthesis (drugs act upon 70S)  Composed of polypeptides and ribosomal RNA Bacterial Cells  ARCHAEA – External Structures  Glycocalyces  Function in the formation of biofilms, adherence  Flagella  For motility  Fimbriae  Non-motile, rod, sticky projection  May have hami (rod with hooks)  Attachment to surfaces Archaea  Archaeal Cell Wall and CM  Most archaea have cell walls  Contain variety of specialized polysaccharides and proteins  All archaea have cytoplasmic membranes  Maintain electrical and chemical gradients  Control import and export of substances from the cell Figure 3.28 Representative shapes of archaea Archaea Archaea  EUKARYOTIC CELLS – External Structure  Glycocalyces  Present in wall-less cells * Not as organized as prokaryotic capsules  Help anchor animal cells to each other  Strengthen cell surface  Provide protection against dehydration  Function in cell-to-cell recognition and communication Eukaryotic Cells  Eukaryotic Cell Walls  Found in fungi, algae, and plants  Cell wall composition:  Plant cell walls have cellulose  Fungal cell walls may be composed of cellulose, chitin, and/or glucomannan  Algal cell walls are composed of a variety of polysaccharides Figure 3.29 A eukaryotic cell wall Eukaryotic Cells  Eukaryotic Cytoplasmic Membranes  ALL EUKARYOTIC CELLS have cytoplasmic membranes  Its properties include:  Control movement of substances into or out of the cell  Contain regions of lipids and proteins, membrane rafts Figure 3.30 Eukaryotic cytoplasmic membrane Eukaryotic Cells  Eukaryotic Flagella  Differ structurally and functionally from prokaryotic flagella  Within the cytoplasmic membrane  May be single or multiple  Generally found at one pole of cell Figure 3.32a Eukaryotic Cells  Eukaryotic Cilia  Shorter and more numerous than flagella  Coordinated beating propels cells through their environment  Also used to move substances past the surface of the cell Figure 3.33b Movement of eukaryotic cilia. Eukaryotic Ribosomes  Larger than prokaryotic ribosomes (80S versus 70S) Eukaryotic Cells Eukaryotic Cells Eukaryotic Cells