[1S] UNIT 1.2 Bacterial Cell Structure Flashcards
PROKARYOTES VS EUKARYOTES: SIZE
0.4-2 um
Prokaryotes
PROKARYOTES VS EUKARYOTES: SIZE
10-100 um
Eukaryotes
PROKARYOTES VS EUKARYOTES: NUCLEAR BODY
Nucleoid in the cytosol
Prokaryotes
PROKARYOTES VS EUKARYOTES: NUCLEAR BODY
Enclosed in a membrane
Eukaryotes
PROKARYOTES VS EUKARYOTES: GENOME
Circular dsDNA (double stranded DNA); In the nucleoid, mesosome
Prokaryotes
PROKARYOTES VS EUKARYOTES: GENOME
Multiple, linear DNA; In the nucleus
Eukaryotes
PROKARYOTES VS EUKARYOTES: EXTRACHROMOSOMAL CDNA
Plasmids, Transposons, Episomes
*These are important in the antibiotic mechanism of the organism
Prokaryotes
PROKARYOTES VS EUKARYOTES: EXTRACHROMOSOMAL CDNA
Mitochondria, Chloroplast
Eukaryotes
PROKARYOTES VS EUKARYOTES: CELL DIVISION
Binary Fission
Prokaryotes
PROKARYOTES VS EUKARYOTES: CELL DIVISION
Mitosis
Eukaryotes
PROKARYOTES VS EUKARYOTES: CELL WALL
PRESENT (except in Mycoplasma and Ureaplasma)
Prokaryotes
PROKARYOTES VS EUKARYOTES: CELL WALL
ABSENT (except in Fungi)
Eukaryotes
PROKARYOTES VS EUKARYOTES: CYTOPLASMIC MEMBRANE
Present (phospholipids and protein)
No sterols present
Prokaryotes
PROKARYOTES VS EUKARYOTES: CYTOPLASMIC MEMBRANE
PRESENT (phospholipids and sterols)
Eukaryotes
PROKARYOTES VS EUKARYOTES: CELL ORGANELLES
- Present
- Absent
- Eukaryotes
- Prokaryotes
PROKARYOTES VS EUKARYOTES: SITE OF ENERGY PROD
Cytoplasmic Membrane or Plasma Membrane
Prokaryotes
PROKARYOTES VS EUKARYOTES: SITE OF ENERGY PROD
Mitochondria (powerhouse of the eukaryotic cell)
Eukaryotes
PROKARYOTES VS EUKARYOTES: SITE OF PROTEIN SYNTHESIS
Free Ribosomes
Ribosomes (70S)
Prokaryotes
PROKARYOTES VS EUKARYOTES: SITE OF PROTEIN SYNTHESIS
Rough ER
Ribosomes (80s)
Eukaryotes
PROKARYOTES VS EUKARYOTES: MOTILITY
Flagella
Prokaryotes
PROKARYOTES VS EUKARYOTES: MOTILITY
Flagella, Cilia, Pseudopod
Eukaryotes
Bacterial cell is made up of
70% Water & 30% Carbohydrates, Proteins, Lipids, Enzymes
Bacterial cell wall structures (2)
Cell envelope structures
Cytoplasmic structures
● Consists of Cell Wall and Cell Membrane
● Some bacteria may also possess capsules and slime layers
Cell Envelope Structures
● Outer membrane (gram-negative only)
● Cell wall (murein layer)
Cell Envelope Structures
CELL ENVELOPE: CELL WALL
Contains a thick layer of
peptidoglycan
Gram-positive
CELL ENVELOPE: CELL WALL
Contains thin layer of peptidoglycan
Gram-negative
CELL ENVELOPE: CELL WALL
Contains waxy substances (e.g. mycolic acids)
Acid fast
CELL ENVELOPE
○ Contains gel-like substances that capture nutrients
○ Contains enzymes needed for detoxification and degradation purposes
Periplasm
CELL ENVELOPE
T/F: Periplasm is distinct in gram-negative
T
CELL ENVELOPE
○ Is the deepest layer of the cell
○ Contains proteins and enzymes that are vital to cellular metabolism
○ Serves as osmotic barrier
Cell Membrane
● Gives shape to the bacterial cell
● Provides protection
Cell Wall
3 types of cell wall
Gram (+), Gram (-) and Acid Fast
Main constituent of cell wall
Peptidoglycan or Murein
Cell wall consists of these 2 alternating disaccharides and are linked by pentapeptides
■ NAG (N-Acetylglucosamine)
■ NAM (N-Acetylmuramic acid)
● Responsible for pathogenicity
● Serves as a point of anchorage of flagella
● Responsible for antigenic characteristic of certain bacteria
Cell Wall
CELL WALL PATHOGENICITY
prevents phagocytosis
M protein
CELL WALL PATHOGENICITY
prevent digestion
Mycolic Acid
● Serves as the target of antimicrobial agents
● Responsible for staining characteristic of the cell
Cell Wall
GRAM (+) VS GRAM (-) CELL WALL
Thick protective murein layer
Gram (+)
GRAM (+) VS GRAM (-) CELL WALL
Thinner Murein Layer (Inner Peptidoglycan Layer)
Gram (-)
GRAM (+) VS GRAM (-) CELL WALL
Presence of (Ribitol/Glycerol phosphate) Teichoic and Lipoteichoic acid (Glycerol Teichoic acid)
Gram (+) Cell Wall
GRAM (+) VS GRAM (-) CELL WALL
Presence of Murein Lipoprotein
Gram (-)
GRAM (+) VS GRAM (-) CELL WALL
No periplasm
Gram (+)
GRAM (+) VS GRAM (-) CELL WALL
Periplasmic space
Gram (-) Cell Wall
GRAM (+) VS GRAM (-) CELL WALL
Antigenic polysaccharide
Presence of S-layer
Gram (+)
GRAM (+) VS GRAM (-) CELL WALL
Outer layer: proteins, phospholipids, and
lipopolysaccharides:
- O-antigen
- Core polysaccharide
- Lipid A (endotoxin)
Gram (-)
GRAM (+) VS GRAM (-) CELL WALL
Flagellum is provided only with two basal rings
Gram (+)
G(+)/G(-): Haemophilus influenzae, Neisseria gonorrhoeae and Bordetella pertussis
Gram (-) Cell Wall
Presence of phospholipids similar in the cell membrane
Gram (-) Cell Wall
Presence of Principal Proteins or Major Outer Membrane Proteins such as
○ Porin Proteins
○ Transmembrane Proteins
○ Peripheral proteins
Gram (-) Cell Wall
GRAM (-) CELL WALL
span the outer membrane
Transmembrane Proteins
GRAM (-) CELL WALL
responsible for transmembrane transport of molecules
Peripheral proteins
appear as WEAKLY GRAM POSITIVE
Acid Fast Cell Wall
Possess a waxy layer of mycolic acid bound to the cell wall
○ Seen in Mycobacterium, Nocardia
Acid Fast Cell Wall
Cell membrane of AF organisms are similar to other bacteria except that they possess _________ & ____________
Phosphatidylmannosides (PIM) and Lipoarabinomannan
ORGANISMS THAT LACK CELL WALL
○ Contains sterol in their cell membranes
○ Seen in various shape microscopically
Mycoplasma and Ureaplasma
ORGANISMS THAT LACK CELL WALL
gram-positive and gram-negative cells that lose their cell walls
○ can grow in media supplemented with serum or sugar to prevent osmotic rupture of the cell membrane
L-forms
● Phospholipid bilayer with embedded proteins
● Composition: 30-60% Phospholipids and 50-70% Protein
Plasma / Cell Membrane
● For protection
● Osmotic barrier
● Site of energy production: electron transport chain
Plasma Membrane
● Chemical components: phospholipids and proteins
● No sterols present
Plasma Membrane
● Folded areas of the cell membrane
● Extensions of the cytoplasmic membrane
Mesosomes
● Site of enzymatic activity
● Point of attachment for nucleoid
Mesosomes
Capsule (organized)
Slime Layer (unorganized)
Surface Polymers
● Generally composed of polysaccharides
● An organized material that is firmly attached to the cell wall
Capsule
○ Protects from toxic substances and desiccation
○ Promotes concentration of nutrients
Capsule
○ Promotes adhesion
○ Antiphagocytic factor
○ Antigenic (K antigen); (Vi antigen seen in S. typhi)
Capsule
Klebsiella pneumoniae
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus influenzae
CAPSULE: Polysaccharide Containing
Bacillus anthracis
CAPSULE: Polypeptide D-Glutamic Acid Containing
Pasteurella multocida
CAPSULE: Hyaluronic Acid Containing
Unorganized layer and not firmly attached to cell wall
Slime Layer
Inhibits phagocytosis or aid in the adherence to host tissue or synthetic implants
Slime Layer
- Organisms capable of producing slime layer
- Also polysaccharide containing
○ Staphyloccocus epidermis
○ Steptococcus mutans
Consists of a monomicrobic or polymicrobic group of bacteria housed in a complex polysaccharide matrix
Biofilm
The cells reach a critical mass that results in alteration in metabolism and gene expression
Biofilm
Why are biofilms important
● Often difficult to detect
● Resistant to desiccation
● Dissemination
● Tolerant to biocides
● Locomotory appendage of the bacterial cell
● Long filamentous appendages
● Organ for Locomotion/Motility
Flagella
Seen mostly in Gr(-) bacilli
Flagella
3 parts of flagella
filament, hook and basal body
seen in Vibrio
Sheathed Flagella
● Protein Composition: Flagellin
● Function: Allows the spread of infection
● Antigen: H Antigen (heat-labile)
Flagella
no flagella
Atrichous
has a singular flagellum on one end
Monotrichous
has multiple (tuft) flagella on one end of the bacterium
Lophotrichous
flagella is evenly distributed on both ends of the bacterium
Peritrichous
contains a single flagellum on both ends of the bacteria
Amphitrichous
3 flagellar stains
● Leifson
● Gray
● Fisher and Conn
FLAGELLA
Motility is best observed at
25°C
Flagella is seen at 2 methods
Hanging Drop Method & Use of Semisolid Media
● Axial Fibril
● Spirochetes (cork-screw motility)
Periplasmic Flagella (Endoflagellum)
● Hairlike, protein structures (2um in length)
● Main purpose is for bacterial adherence and conjugation
● Non-motile, long hollow proteins
Pili
PILI
Promotes bacterial adherence
Common/Somatic Pili/Fimbriae
PILI
Allows genetic exchange between two bacterial cells
Sex Pili
● Escherichia coli
● Neisseria gonorrhoeae
● Neisseria meningitidis
● Pseudomonas aeruginosa
● Some Gr(+) organisms such as: Actinomyces, some Streptococci, and Corynebacteria
Fimbrae
Amorphous gel containing enzymes, granules, inclusions, genome
Cytoplasm
CYTOPLASMIC STRUCTURES
Chromatin or nuclear body composed of a single circular DNA
Nucleoid
CYTOPLASMIC STRUCTURES
Appear as free or attached to the cell membrane
Ribosomes
CYTOPLASMIC STRUCTURES
NUCLEOID
RIBOSOMES
ENDOSPORES
TRANSPOSONS & PLASMIDS
CYTOPLASMIC GRANULES
CYTOPLASMIC STRUCTURES
Produced during harsh environmental conditions to protect itself against them, such as temperature change, dessication, high exposure to gamma radiation and chemical agents
Endospores
CYTOPLASMIC STRUCTURES
Multilayered, small, dormant asexual spores
Endospores
CYTOPLASMIC STRUCTURES
● HIGHLY RESISTANT IN UNFAVORABLE CONDITIONS
● COMPOSITION: Dipicolinic acid calcium complex
Endospores
CYTOPLASMIC STRUCTURES
● Stained/Visualized by Fulton-Schaeffer Method
● Medically Important Genera with spores:
○ Bacillus
○ Clostridium
Endospores
“Jumping genes”
Transposons
DNA elements that are able to “JUMP” or TRANSPOSE from one chromosome or plasmid to another
Transposons
Function: Carry antibiotic resistance genes
Transposons
● Circular DNA elements
● Replicate independently from the chromosome
Plasmids
Carry genes that give the bacterium an advantage
Plasmids
Serve as food reserves (polysaccharides, lipids, polyphosphates)
Inclusion Bodies
INCLUSION BODIES
Major storage material for Enterics
Glycogen
INCLUSION BODIES
Principal storage material for Neisseria and
Clostridium
Starch
INCLUSION BODIES
seen in Bacillus and
Pseudomonas
Poly-beta hydroxybutyrate
BACTERIA AND THEIR INCLUSION BODIES
Much Granules
Mycobacterium tuberculosis
BACTERIA AND THEIR INCLUSION BODIES
● Babes Ernst Bodies
● Metachromatic Granules
● Volutin
Corynebacterium diptheriae
BACTERIA AND THEIR INCLUSION BODIES
Halberstaedter Prowazek
Bodies
Chlamydia trachomatis
BACTERIA AND THEIR INCLUSION BODIES
Levinthal Cole Lillie Bodies
Chlamydia psitaci
INCLUSION BODIES
contains sulfur containing granules
Thiobacillus
● Causative organism of Black Plague
● “Safety pin appearance”
● Caused by Bipolar bodies
Pasteurella multocida and Yersinia pestis
CLASSES OF DYES
● Cationic/(+) charged groups that bind to (-) charged molecules
● It will stain the acidic structures.
Basic Dyes
CLASSES OF DYES
methylene blue, basic fuchsin, crystal violet, safranin, malachite green
Basic Dyes
CLASSES OF DYES
● Anionic/(-) charged groups that bind to (+) charged
molecules
● It will stain the basic structures
Acid Dyes
STAINING PROCEDURES
● 1 stain is used
● Stains/Visualizes the form and shape of the bacterial cell
Simple Staining (basic/simple dyes)
STAINING PROCEDURES
methylene blue, basic fuchsin, crystal violet, safranin, malachite green
Simple Staining (basic/simple dyes)
STAINING PROCEDURES
use of 2 or more dyes
Differential Stain
STAINING PROCEDURES
Gram Staining, Acid-Fast Staining
Differential Stain
STAINING PROCEDURES
Primarily to demonstrate the capsule
Indirect / Relief / Negative Staining
STAINING PROCEDURES
● Bacteria appear as light-colored bodies against a dark background
● “Halo” appearance
● Used to visualize capsulated bacteria such as Klebsiella pneumoniae
Indirect / Relief / Negative Staining
STAINING PROCEDURES
India Ink
Indirect / Relief / Negative Staining
STAINING PROCEDURES
● Used for staining special structures
● Stains for specific parts of a bacterial cell
Special Stains
STAINING PROCEDURES
Special stain for cell wall
Dyar Stain
STAINING PROCEDURES
Special stain for Metachromatic Granules/Inclusion Bodies
Neisser, Albert
STAINING PROCEDURES
Special stain for Endospores
Fulton Schaeffer, Dorner
STAINING PROCEDURES
Special stain for Flagella
Gray, Leifson
STAINING PROCEDURES
Special stain for DNA
Feulgen
STAINING PROCEDURES
Special stain for Spirochetes
Levaditi’s
STAINING PROCEDURES
● More sensitive as compared to routine stains
● Use of fluorochromes such as acridine orange,
rhodamine-auramine (Truant Method for M. tuberculosis) and fluoroscein isothiocyanate (FITC), calcofluor white
Fluorescent Dyes
● Fundamental Staining Method in Bacteriology
● Developed by Hans Christian Gram
Gram Staining
Gram staining involves the use of (4)
Primary Stain
Mordant
Decolorizer
Secondary Stain
Developed gram staining
Hans Christian Gram
GRAM STAIN
Primary Stain: Crystal Violet - V
Mordant: Gram’s Iodine - V
Decolorizer: 95% Ethanol or Acetone Alcohol - V
Secondary Stain: Safranin O or Carbol Fuchsin - V
Gram (+)
GRAM STAIN
Primary Stain: Crystal Violet - V
Mordant: Gram’s Iodine - V
Decolorizer: 95% Ethanol or Acetone Alcohol - Colorless
Secondary Stain: Safranin O or Carbol Fuchsin - Red/Dark Pink
Gram (-)
Staining method for bacteria that possess mycolic acid in their cell walls (i.e. Mycobacterium tuberculosis and other species, and Nocardia)
Acid Fast Staining
Principle: Mycolic acid, once stained by the primary stain, is able to resist the decolorization of acid-alcohol rendering them as “ACID FAST”
Acid Fast Staining
AF METHODS
● Primary Stain: Carbolfuchsin
● Mordant: Heat/Steam
● Decolorizer: Acid-alcohol
● Secondary Stain: Methylene Blue/Malachite Green
Zhiel-Neelsen - Hot Method
AF METHODS
● Primary Stain: Carbolfuchsin
● Mordant: Tergitol
● Decolorizer: Acid Alcohol
● Secondary Stain: Methylene Blue/Malachite Green
Kinyoun Method - Cold Method