Download BIO 221

BIO 411
Chapter 3 – Bacterial Morphology
and Cell Wall Structure and
Synthesis
Prokaryote vs. Eukaryote
 Get with a partner and make a list of the
differences between Prokaryotes and
Eukaryotes.
 List differences on board
 Amazing cell size demo!
Shapes of Bacteria
 Almost all bacteria have one of three
morphologies (or shapes):
 coccus - spherical-shaped (pl., cocci)
 Diplococcus
 Streptococcus
 Staphylococcus
 bacillus - rod-shaped (pl., bacilli)
 spirillum - spiral-shaped (pl., spirilla)
 Figure 3-3 B
Gram Stain
 Gram Stain
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Crystal violet
Iodine
Decolorizer (EtOH or Acetone)
Safranin
 Gram + vs. Gram – cells
 “P” – purple, positive
 Figure 3-3 A
 Only dependable on new cultures (24hr)
Bacterial Cell Structure
 Typical prokaryotic cell - Figure 3.1
 Inside-Out Approach
 What is the cytoplasm?
 ~80% water
Cytoplasm
 Also contains:
 The bacterial chromosome (structure?)
 It is about 1mm long (1000X longer than the cell)
 It’s localized in the nucleoid
 Plasmids – small circular pieces of nonchromosomal DNA
 Functions?
 Ribosomes (70S) – function?
 Protein synthesis
Cytoplasm
 Cytoplasmic membrane – typical lipid
bilayer
 Carries out many functions associated with
eukaryotic organelles
 Mesosome – anchor to separate daughter
chromosomes during cell division
 Figure 3-1
Bacterial Cell Structure (cont.)
 Next layer: Bacterial Cell Wall
 Composed of sub-units found nowhere
else in nature
 site of action of some of the most
effective antibiotics
 cell wall determines a cell’s morphology
 Primary Function – protect cell from
exploding (osmotic pressure)!!!
Bacterial Cell Structure (cont.)
 Cell Wall Structure
 Bacterial cell walls are composed of
peptidoglycan
 the glycan portion of peptidoglycan is made of a
huge polymer of carbohydrates containing:
 N-acetylmuramic acid (NAM) and
 N-acetylglucosamine (NAG)
 These long chains of alternating NAM and NAG
are held together by short peptide cross-bridges
 log raft analogy
Gram+ vs. Gram- Cell Walls
 Gram+ cells have a very thick, multilayered
cell wall
 they also contain teichoic acids and lipoteichoic
acids
 Lysozyme
 Figure 3-2 A
 Gram- cells have a very thin layer of
peptidoglycan
 they also have an outer membrane in addition to
the cytoplasmic membrane
 the space between these two membranes is called
the periplasmic space or periplasm
Gram+ vs. Gram- Cell Walls (cont.)
 the outer membrane is an asymmetric bilayer:
 Phospholipids on the inside
 lipopolysaccharides (LPS) on the outside
 LPS structure:
 Lipid A - also called endotoxin because it
damages cells and tissues (also causes fever
and shock)
 Core Polysaccharide
 O antigen – distinguishes serotypes of a
species (E. coli O157:H7)
 Figure 3-10
Gram+ vs. Gram- Cell Walls (cont.)
 Porins allow non-specific transport across the
membrane
 Figure 3-2 B
 Basis for the Gram stain reaction (Figures 3-2
and 3-3 A)
Bacterial Cell Structures
 Capsule outer coating of sticky
polysaccharide or protein
 Also called a glycocalyx or slime layer
 Functions?
 Antiphagocytic and poorly antigenic Streptococcus pneumoniae
 Adherence - Streptococcus mutans and
dental caries, many other examples too!
 Biofilm - protection
Movement of Prokaryotic Cells
 Flagella - ropelike propeller composed of
flagellin
 Chemotaxis
 bacteria can move toward nutrients or away
from toxic substances
 Mechanism – “swim and tumble”
Attachment of Prokaryotic Cells
 Bacteria can use fimbriae and pili to attach
to surfaces and other cells
 fimbriae are numerous, short protein
filaments of attachment (E. coli and
Neisseria gonorrhoeae)
 pili are long protein filaments for attachment
of bacteria to other bacterial cells
 Used for DNA transfer
 Figure 3-4
Mycobacteria and Mycoplasmas
 Mycobacteria have a peptidoglycan cell
wall, but they contain an outer covering
of mycolic acid
 Antiphagocytic
 Acid-fast stain
 Mycoplasmas do not have a cell wall
Bacterial Endospores
 Some types of Gram+ bacteria have the
ability to form endospores
 Primary genera Bacillus and Clostridium
 the endospore is the “navy seal” of living
organisms
 Vegetative State vs. Endospore
 Endospore production – Figure 3-12
Bacterial Endospores (cont.)
 Endospore germination
 Important Point:
 endospores are not a means of reproduction
 Importance of endospores
Disease of the Day
 Anthrax
 Etiology – Bacillus anthracis (via toxins)
 Aerobic, endospore-forming,
 Reservoir – Contaminated animals (herbivores)
and animal products
 Transmission and Development
 Cutaneous anthrax – through a cut in the skin
 Figure 25-3, page 268
 20% mortality w/o treatment, less than 1% with
 Gastrointestinal anthrax – rare (~100% mortality)
Disease of the Day
 Inhalational or Pulmonary anthrax – endospores
inhaled
 Can show 2 or more months of latency
 Days 1-2 mild fever, cough, chest pain (non-specific)
 Death usually occurs within 3 days w/o treatment
 Almost 100% mortality
 Lab ID: microscopy and specific antigen
detection
 Prevention and Control
 vaccine (6 initial + yearly booster)
 antibiotics effective if given in time
Cell Structure Review
 Find a partner and review the structure of
bacterial cells
Endosymbiosis
 The Theory of Endosymbiosis
 Supporting Evidence:
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Mitochondrial DNA
70S ribosomes
Binary Fission
RNA sequencing