1. Lipid A 2. Core polysaccharide region 3. O-antigen

Component Of A Bacteria Flashcards by Lucy Ferragamo

What are the components of a bacteria?

Cell wall
Plasma membrane
Cytoplasm
Components external to the cell

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One of the most important structures
Layer that is usually fairly rigid that lies outside the plasma
membrane

Confers shape
Protects the cell from osmotic lysis
Anchors the flagellum
Adds to the pathogenicity of the cell
Protects the cell from toxic substances and pathogen
Used in identification

Cell wall

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Why is gram positive violet/blue stain while gram negative is red stain?

The peptidoglycan layer enables the differentiation with the gram staining action. In gram positive, the peptidoglycan layer only absorbs the crystal violet stain –giving the violet/bluish color. In gram negative, when the colorizer is applied, because of the very thin peptidoglycan layer, the crystal violet is being washed off. And then, when the counterstain, safranin, which is red in color is applied, it gives off a red stain.

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CHARACTERISTICS OF A GRAM POSITIVE (+) CELL WALL

Thick layer of peptidoglycan
Presence of Teichoic acid
Other substances found in cell wall

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what are the other substances found in cell wall?

Teichuronic acid
Neutral polysaccharides
Other glycolipids
Mycolic acids

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Refers to the major composition of the cell wall.

Peptidoglycan

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Peptidoglycan subunit

Peptidoglycan subunit:
1. N-acetylglucoseamine (G)
2. N-acetylmuramic acid (M)
3. L-alanine
4. D-glutamic acid
5. D-alanine
6. Meso-diaminopimelic-acid

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the one responsible for the gram positivity of microorganism. Because of its presence in the peptidoglycan layer, it retains the crystal violet stain.

Teichoic acid

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Linear polymers of 16-40 phosphodiester-linked
glycerophosphate residues covalently linked to the cell membrane

Lipoteichoic acid (LTA)

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These are the
viruses that infects bacteria.

Bacteriophages

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Periplasmic space in gram (+) and (-)

(+) plasma membrane and cell wall
(-) plasma membrane and outer membrane

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Characteristics of a gram negative (-) cell wall includes thin layer of peptidoglycan and what outer membranes

Lipopolysaccharides (LPS)
Lipoproteins
Porins

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Lipopolysaccharides (LPS) contains High toxin.
NOTE: The difference between gram positive and gram negative is:
Gram negative: the LPS would be released after the microorganism is already ______
Gram positive: the LPS is released continuously while the microorganism is_______

(+) alive
(-) already dead

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3 parts of LPS

Lipid A
Core polysaccharide region
O-antigen

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In E. coli and Salmonella typhimurium: fatty acids are

β-hydroxymyristic acid (3-hydroxytetradecanoic acid)

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Composed of 2 glucosamine residues linked β-1,6 (backbone) with four identical fatty acids

Lipid A

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Inner core of the polysaccharide region consists of

2-keto-3-deoxyoctonate (KDO) 2. Heptose
Ethanolamine
Phosphate

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− Short polysaccharide extending outward from the core
− Consists of peculiar sugars which varies between bacterial strains
− NOT essential for viability

O-antigen

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Importance of Lipopolysaccharides (LPS)

 Avoidance of host defenses (O-antigen)
 Contributes to the negative charge on the cell’s
surface.
 Stabilizes membrane structure
 Act as endotoxin

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 Mediate interconnection between OM and
murein
 Synthesized within the cell and contains a
leader sequence of 20 amino acids at its amino
terminal end
 After transport through the CM, the leader
sequence is removed and the terminal residue
is modified to make it hydrophobic
 Facilitates integration to the OM

Lipoproteins

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Small holes in the cell wall

Porins

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Importance of outer membrane

 Proteins in OM are used as attachment sites
by bacteriophages
 Permeability barrier to heavy metals, lipid-
disrupting agents and larger molecules
There are heavy metals that are toxic to the bacteria.
 Outer surface with strong negative charge is important in evading phagocytosis

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Space between the cell wall and the peptidoglycan layer (aqueous compartment)

Periplasm

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Space between the cell wall and the peptidoglycan layer (aqueous compartment)

Periplasm

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Activities of periplasm

 Redox reactions For transport of materials  Osmotic regulations So that limited materials would enter. Otherwise, it would lead to shrinkage or the cell would burst.  Solute transport  Protein secretion  Hydrolysis

Composition of plasma membrane

1. Phospholipid 2. Proteins 3. Hopanoids

In phospholipid, most membrane associated lipids are

Structurally asymmetric

Parts of phospholipid

Phosphatidylethanolamine Phosphatidylglycerol Fatty acids

Major phospholipid in the cytoplasmic membrane

Phosphatidylethanolamine

Phosphatidylethanolamine is formed from

Glycerol-3-P Serine Fatty acids 1:1:2

Phosphatidylglycerol, next most prevalent is formed from

Glycerol-3-P Serine Ratio is equimolar

Part of phospholipid that varies depending on the species and environmental conditions

Fatty acids

2 types of proteins

A. Integral proteins B. Peripheral proteins

− embedded in the CM − Amphipathic − bound to the fatty acids of the phospholipids via hydrophobic bonding

Integral proteins

− attached to membrane surfaces by ionic interactions

Peripheral proteins

− Rigid, planar molecules found associated with bacterial CM − Molecules similar to sterol

Hopanoids

− Most widely accepted model of the CM − Shows that the CM is a lipid bilayer with which proteins and lipids “float” freely

Fluid Mosaic Model

The fatty acid responsible for the fluidity of the cytoplasmic membrane is the

unsaturated acids.

What is the component of the lipid bilayer?

Phosphatidylcholine and phosphatidylethanolamine

Prokaryotic cytoskeleton

Cresentin FtsZ MreB

− Invaginations of the plasma membrane in the shape of vesicles, tubules, or lamellae − Believed to be involved in:  cell septum formation electron transport  photosynthesis  cell wall formation  DNA replication  Segregation and sporulation

Mesosomes

− Complex structures made of both protein and ribonucleic acid − Present in the cytoplasmic matrix or loosely attached to the plasma membrane − Site of protein synthesis

Ribosomes

Characteristics of a bacterial chromosomes

1. Circular 2. Very tightly-coiled 3. Histones are absent

Granules and Globules

1. Glycogen 2. Poly- β - hydroxyalkanoates 3. Cyanophycin granules 4. Carboxysomes 5. Chlorosomes 6. Polyphosphate granules 7. Sulfur granules 8. Gas vesicles 9. Magnetosomes

Aids in orienting bacteria in the earth’s magnetic field

Magnetosomes

− Small, hollow, cylindrical structures composed entirely of a single small protein − Impermeable to water but freely permeable to gases

Gas vesicles

− Used to store sulfur temporarily − Accumulate in the periplasmic space of in special cytoplasmic globules − Can be found in sulfur bacteria

Sulfur granules

− Linear polymer of orthophosphates joined by ester bonds − Functions as storage reservoir for phosphates or as energy reserve − Can be found in Mycobacterium tuberculosis or Corynebacterium diphtheriae

Polyphosphate granules

− Ellipsoidal vesicles where photosynthetic pigments are located − Attached to the plasma membrane but not continuous with it − Can be seen in photosynthetic bacterias.

Chlorosomes

− Polyhedral bodies about 100 nm in diameter − Containing the enzyme ribulose-1-5- bisphosphate carboxylase − May serve as site for CO2 fixation

Carboxysomes

− Composed of large polypeptides containing approximately equal amount equal amount of amino acids arginine and aspartic acid

Cyanophycin granules

− Also: PHB − Contains β –hydroxybutyrate molecules joined by ester bonds

Poly- β - hydroxyalkanoates

− A polymer of glucose units composed of long chains formed by α(1-4) − Reservoir of food of bacteria

Glycogen

If it is a photosynthetic bacteria it has

Carboxysomes

Components of the cell wall

Glycocalyx Pili/Fimbrae

Glycocalyx layers

1. Capsule 2. Slime layer

 Well-organized glycocalyx  Attached firmly to the cell wall  Compact  Excludes particles like India Ink

Capsule

 Zone of diffused, unorganized material  Loose association  Does not exclude particles

Slime layer

Importance of glycocalyx

 Exclude viruses and most hydrophobic toxic substances  Protection from physical injury  Aid attachment to surfaces  Provide resistance to phagocytes  Reservoir of stored food  Prevent desiccation  Confers pathogenicity  “Cellular garbage dump”  Antigenicity

− Hair-like structures on the surfaces of prokaryotic cells − Composed of protein subunits called “pilins”

Pili/Fimbrae

Types of pili

Adhesion pili Conjugation pili

 Involved in attachment of cells to surfaces  Composed of a single protein  Major determinant of bacterial virulence up to 1000 per cell IF THE BACTERIA HAS THIS, THE RATE OF INFECTION IS FAST

Adhesion pili

 Vehicles for transfer of genetic information between bacteria  Composed of phosphoglycoprotein  About 1 to 10 per cell

Conjugation pili

− Thread-like locomotor appendages extending outward from the plasma membrane and cell wall − Slender, rigid structures about 20 nm across and 15-20 μm long − Rotary structure driven from a motor at the base, with the filament acting as the propeller

Bacterial flagella

The attachment of flagella is deep in the

Plasma membrane

The movement of the flagellated microorganisms are so called the

“tumbling movement”

Filament  A hollow rigid cylinder constructed if a single protein called

Flagellin

Types of flagella

1. Monotrichous 2. Amphitrichous 3. Lophotrichous 4. Petrichous 5. Atrichous

found inside the cytoplasm [bailey & scott’s 15th ed] − A type of dormant cell formed by some groups of bacteria − A cryptobiotic − Highly resistant to environmental stresses If they encounter a very harsh environment, they would transform themselves into spores. But not all can be turned to spores. It depends on the species and their genes. − Formed by vegetative cells in response to environmental signals that indicate a limiting factor for vegetative growth − A mechanism of survival

Bacterial endospore

Location of spores

Terminal spores Central spores Subterminal spores

Component Of A Bacteria Flashcards

(70 cards)