BACTERIAL CELL STRUCTURE Flashcards
PPT and Discussion based
No nucleus
Prokaryote
Gram Positive
Nucleoplasam concentrated nuclear elements
Gram negative
For survival
Binary Fission
Prokaryotes
For growth
Eukaryotes
0.4-2um
Prokaryotes
10-100um
Eukaryotes
Nuclear Body
Nucleoid in the cytosol
Prokaryotes
Nuclear body
Enclosed in a membrane
Eukaryotes
Genome
Circular dsDNA; In the nucleoid, mesosome
Prokaryotes
Genome
Multiple, linear DNA
in the nucleus
Eukaryotes
Extrachromosomal Circular DNA
Plasmids, Transposons, Episomes
Prokaryote
Extrachromosomal Circular DNA
Mitochondria, chloroplast
Eukaryotes
Cell division
Binary fission
Prokaryotes
Cell division
Mitosis
Eukaryotes
Cell wall
PRESENT (except in mycoplasma and ureaplasma)
Prokaryotes
Cell wall
ABSENT (except in fungi)
Eukaryotes
Cytoplasmic membrane
Present (phospholipids and PROTEIN)
Prokaryotes
Cytoplasmic membrane
Present (phospholipids and STEROLS)
Eukaryotes
Cell organelles
ABSENT
Prokaryotes
Cell organelles
PRESENT
Eukaryotes
Site of energy production
Cytoplasmic Membrane
Prokaryotes
Site of energy production
Mitochondria
Eukaryotes
Site of protein synthesis
Free ribosomes
Size: Ribosomes 70S
Prokaryotes
Site of protein synthesis
Rough ER
Size: RIbosomes 80s
Eukaryotes
Motility
Flagella
Prokaryotes
Motility
Flagella, Cilia, Pseudopod
Eukaryotes
70% water
30% carbohydrates, proteins, lipids, enzymes
Bacterial cell
Cell envelope structures
Basic structure
Outer: Cell wall
Cytoplasmic structures
No organelles
Inner
Ribosomes in fungi
80s
Ribosomes in Parasites
80s
Ribosomes in viruses
Absent
Ribosomes in bacteria
70s
Cell wall
No
Viruses
Cell wall
Yes
Bacteria
Fungi
Cell wall
+/-
Parasites
Nucleic acid
Either DNA or RNA
Viruses
Nucleic acid
Both DNA and RNA
Bacteria
Fungi
Parasites
Type of nucleus
None
Viruses
Type of nucleus
No distinct nuclear component
Bacteria
Type of nucleus
Membrane-bound nucleus
Fungi
Parasites
Mitochondria
Absent
Viruses
Bacteria
Mitochondria
Present
Fungi
Parasites
Nature of outer surface
Protein capsid and lipo-protein envelope
Viruses
Nature of outer surface
Rigid wall containing peptidoglycan
Bacteria
Nature of outer surface
Rigid wall containing chitin
Fungi
Nature of outer surface
Flexible membrane
Parasites
Motility
None
Viruses
Fungi
Motility
Some
Bacteria
Motility
Most
Parasites
Method of replication
Not binary fission
Viruses
Method of replication
Binary fission
Bacteria
Method of replication
Budding or mitosis
Fungi
Method of replication
Mitosis
Parasites
Cell envelope structures
Consists of cell wall and cell membrane
Cell envelope structures
Cell envelope structures
Does not have cell wall and cell membrane
myoplasma and ureaplasma
Cell envelope structures
Some bacteria may also possess
capsules and slime layers
(resistance, adds on protective barrier)
Cell wall in bacteria is mainly composed on
peptidoglycans
Structure rigidity
Strength structural rapport
Maintains shape of cell
Peptidoglycans
Cell wall
murein layer/mucopeptide
Outer membrane
Gram negative only
Contains a thick layer of peptidoglycan
Gram positive
(POSITIVE PURPLE; making it difficult to decolorize, sticking to the purple color)
Contains thin layer of peptidoglycan
Gram negative
Contains waxy substances (e.g mycolic acids)
Acid fast
Distinct in gram negative
Periplasm
Contains gel-like substances that capture nutrients
Periplasm
Contains enzymes (to metabolize nturients for bacteria)
Periplasm
Deepest layer of the cell
Cell membrane
contains proteins and enzymes that are vital to cellular metabolism
Cell membrane
Serves as osmotic barrier
Cell membrane
Give shape to the bacterial cell
Provides protection
Cell wall
3 types of cell wall
Gram +
Gram -
Acid fast
Main constituent of cell wall
Peptidoglycan or Murein
Main constituent: Peptidoglycan or Murein
Consisting of alternating dissacharides
NAG (N-actyl glucosamine)
NAM (N-actyl muramic acid)
(Sugards Chained with AAs)
Main constituent: Peptidoglycan or Murein
Linked by
Pentapeptides (5 AAs)
responsible for pathogenecity
Cell wall
M protein
Prevents phagocytosis
(to adhere itself, phagosome formation)
Virulent factor
Mycolic Acid
Prevent digestion
(used by mycobacterium; acid fast)
Serves as a point of anchorage of flagella
Cell wall
Responsible for antigenic characteristic of certain bacteria
Cell wall
Serves as the target of antimcrobial agents
Cell wall
Responsible for staining characteristic of the cell
Cell wall
Thick protective murein layer
Presence of (Ribitol/Glycerol Phophate) Teichoic and Lipoteichoic acid (glycerol teichoic acid)
Gram positve
No periplpasm
Gram positive
Antigenic polysaccharide
Presence of s-layer
Gram positive
Thinner murein layer (inner peptidoglycan layer)
Presence of murein lipoprotein
Gram negative
Periplasmic space
Gram negative
Outer layer:Proteins, Phospholipids and Lipopolysaccharides
O-antigen
Core polysaccharide
Lipid A (endotoxin)
Gram negative
Certain Gr neg organisms (Haemophilus influenzae, Neisseria gonorrheae, and Bordetella pertussis) have no LPS but instead have
Lipo-oligosaccharides (LOS)
Presence of phospholipids similar in the
cell membrane
Contains Lipid A and oligosaccharide core but no O antigens
Lipo-oligosaccharides (LOS)
Presence of principal proteins or major outer membrane proteins such as
Porin proteins
Transmembrane Proteins (span the outer membrane)
Peripheral proteins (responsible for transmembrane transport of molecules)
Weakly gram positive
Acid fast organisms
Possess a waxy layer of mycolic acid bound to the cell wall (seen in mycobacterium, nocardia)
Acid fast cell wall
Difficult to stain
Hydrophobic
Cell membrane of Acid fast organisms are similar to other bacteria except that they possess:
Phosphadylamannosides (PIM) and Lipoarabinomannan
Mycoplasma and Ureaplasma contains ___ in their cell membranes
Sterol
Organisms that lack cell wall
Mycoplasma and ureaplasma
Seen in various shape microscopically
Mycoplasma and ureaplasma
Gram positive and gram negative cells that lose their cell walls
L-forms
Can grow in media supplemented with serum or sugar to prevent osmotic rupture of the cell membrane
L-forms
Phospholipid bilayer with embedded proteins (phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol)
Plasma membranae
30-60% phospholipids
59-70% protein
Plasma membrane
For protection
Osmotic barrier
Plasma membrane
Site of energy production of plasma membrane
Electron transport chain
Chemical components of plasma membrane
Phospholipids and proteins
No ___ present in plasma membrane
sterols
Folded areas of the cell membrane
Mesosomes
Extensions of the cytoplasmic membrane
Mesosomes
Site of enyzmatic activity
Mesosomes
Point of attachment for nucleoid
Mesosomes
Surface polymers
Capsule
Slime layer
generally composed of polysaccharides
Capsule
organized material
firmly attached to cell wall
capsule
Protects from dessication and toxic materials
Promotes concentration of nutrients
Promotes adhesion
Antiphagocytic
Antigen K antigen); (Vi antigen seen in S. typhi)
Functions of capsule
Capsule polysaccharide containing
Klebsiella pneumoniae
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus influenza
Polypeptide D-glutamic acid containing
Bacillus anthracis
Hyaluronic Acid containing
Pasteurella multocida
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
Slime layer polysaccharide containing
Staphylococcus epidermidis
Streptococcus mutans
Consists of monomicrobic or polymicrobic group of bacteria housed in a complex polysaccharide matrix
Biofilm
During biofilm formation the cells reach a critical mass that results in
alteration in metabolism and gene expression
Why are bioflims important
Often difficult to detect
Resistant to desiccation
Dissemination
Tolerant to Biocides
Long filamentous appendages
Organ for locomotion/motility
Flagella
Seen mostly in Gr- bacilli
3 parts
Filament
Hook
Basal Body
Seen in vibrio
Sheathed flagella
Protein composition of flagella
flagellin
Function of flagella
allows the spread of infection
Flagella antigen
H antigen
Tail
Atrichous
None
Tail
Monotrichous
one
Tail
Lopotrichous
Multiply in tops at one end
Tail
Amphitrichous
both ends
Tail
Peritrichous
Many
Flagellar stains
Leifson
Gray
Fisher and Conn
Motility of flagella is best observed at
25 degrees celsius
Flagella is seen in
Hanging drop method
use of semisolid media
Periplasmic flagella (endoflagellum)
Axial Fibril
Spirochetes motility
Cork-screw motility
Hairlike, protein structure (2um in length)
Pili
Nonmotile, long hollow proteins
Pili
Two types of pili
Common/Somatic Pili/Fimbriae
Sex Pili
Escherichia coli
Neisseria gonorrhoeae
Neisseria meningitidis
Pseudomonas aeuriginosa
Some Gr+ organisms such as: Actinomyces, some streptococci and corynebacteria
Fimbriae
Amorphous gel containing enzymes, granules, inclusions, genome
Cytoplasm
Nucleoid
RIbosomes
Endospores
Transposons and Plasmids
Cytoplasmic granules
Cytoplasmic structures
Chromatin or nuclear body composed of single circular DNA
Nucleoid
Appear as free or attached to the cell membrane
Ribosomes
Size of ribosomes in cytoplasm
70s
Produced during harsh conditions
Endospores
Multilayered, small, dormant asexual spores
Highly resistant in unfavorable conditions
Endospores
Composition of endospores
Dipicolinic acid calcium complex
Endosposres is stained/visualized by
Fulton-Schaeffer Method
Endospores medically important genera
Bacillus
Clostridium
“Jumping genes”
Transposons
DNA elements that are able to “JUMP” or TRANSPOSE from one chromosome or plasmid to another
Transposons
Carry antibiotic resistance genes as function
Transposons
Circular DNA elements
Plasmids
Replicate independently from the chromosome
Plasmids
Carry genes that give the bacterium an advantage
Plasmids
Serve as food reserves (polysaccharides, lipids or polyphosphates)
Inclusion bodies
Major storage material for enterics
Glycogen
Principal storage material for neisseria and clostridium
Starch
Seen in bacillus and pseudomonas
Poly-beta hydroxybutyrate
Much granules
Mycobacterium tuberculosis
Babes Ernst Bodies/Metachromatic Granules/Volutin
Corynebacterium diphteriae
Halberstaedter Prowazek bodies
Chlamydia trachomatis
Levinthal Cole Lillie Bodies
Chlamydophila psitaci
Contains sulfure containing granules
Thiobacillus
Bipolar bodies
“Safety pin appearance”
Pasteurella multocida and Yersinia Pestis
Classes of dyes
Basic dyes
Acid dyes
Cationic/(+) charged groups that bind to (-)charged molecules
Basic dyes
Metheylene blue, basic fuchsin, crystal violet, safranin, malachite green
Basic dyes
Anionic/ (-) charged groups that bind to (+) charged molecules
Acid dyes
eosin, rose bengalm acid fuchsin
Acid dyes
1 stain is used
SImple staining
Stains/visualizes the form and shape of the bacterial cell
Simple staining
use of 2 or more dyes
Differential stain
Gram staining, acid-fast staining
Differential stain
Primarily to demonstrate the capsule
Indirect/Relief staining/ Negative staining
Bacteria appear as light-colored bodies against a dark background
“Halo” appearance
Indirect/Relief staining/Negative staining
Used to visualize capsulated bacteria such as klebsiella pneumoniae
Indirect/Relief staining/Negative staining
India Ink
Indirect/Relief staining/Negative staining
Stains for a specific parts of a bacterial cell
Special stains
Dyar stain
Neisser, Albert
Fulton Schaeffer, Dorner
Gray, Leifson
Feulgen
Levaditi’s
Examples of special stains
Dyar stain
Cell wall
Neisser, Albert
Metachromatic Granules
Fulton Schaeffer, Dorner
Endospores
Gray, Leifson
Flagella
Feulgen
DNA
Spirochetes
Levaditi’s
Use of fluorochromes such as acridine orange, rhodamine-auramine, and fluoroscein isothiocyanate, calcofluor white
Use of fluorescent dyes
Truant method for M. tuberculosis
Rhodamine-auramine
FITC
Fluotoscein isothiocyanate
more sensitive as compared to routine stains
use of fluoroscent dyes
Fundamental staining method in bacteriology
Gram staining
Developed by hans christian gram
Gram staining
Gram staining involves the use of
Primary stain
Mordant
Decolorizer
Secondary stain
Primary Stain
Crystal violet
Gram (+) ✓
Gram (-) ✓
Mordant
Gram’s iodine
Gram (+) ✓
Gram (-) ✓
Decolorizer
95% ethanol or acetone-alcohol
Gram (+) ✓
Gram (-) colorless
Secondary stain
Safranin or Carbol Fuchsin
Gram (+) ✓
Gram (-) Red/dark pink
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 of acid fast staining
Mycolic acid, once stained by the primary stain is able to resist the decolorization of acid-alcohol rendering them as “ACID FAST”
Methods of Acid fast staining
Ziehl-Neelsen (Hot method)
Kinyoun Method (Cold method)
Ziehl neelsen
Primary stain
Carbolfuchsin
Ziehl-Neelsen
Mordant
Heat/steam
Ziehl-Neelsen
Decolorizer
Acid-alcohol
Ziehl-Neelsen
Secondary stain
Methylene blue/malachite green
Kinyoun method
Primary stain
Carbolfuchsin
Kinyoun method
Mordant
Tergitol
Kinyoun method
Decolorizer
Acid alcohol
Kinyoun method
Second stain
Methylene blue/malachite green
Decolorizer
NAF
Colorless
Secondary stain
NAF
Blue
