Topic 2: General Characteristics of Bacteria

Bacteria

• unicellular organisms that lack a nuclear membrane and true nucleus

• classified as prokaryotes (Greek: before kernel [nucleus]), having no mitochondria, endoplasmic reticulum (ER), or Golgi bodies

0.25- 1

1-3

Most clinically relevant bacterial species range in size from ____-____ μm in width and ___ μm in length

1. Cocci - circular

2. Coccobacilli - ovoid

3. Bacillus - rod shaped

4. Fusiform - tapered, pointed ends

5. Curved

6. Spiral - helical, like corkscrew

7. Pleomorphic  no defined shape

7 COMMON BACTERIAL CELLULAR MORPHOLOGIES

a. Pairs
b. Chains
c. Grape-like clusters
d. Group of four
e. Packets of eight
f. Palisades
g. Chinese characters

8 BACTERIAL ARRANGEMENT

Cell Evelope

• outermost structure, comprises:

A. Outer membrane
in gram-negative bacteria only

B. Cell wall
composed of the peptidoglycan macromolecule (murein layer)

C. Periplasm
in gram-negative bacteria only

D. Cytoplasmic or cell membrane
encloses the cytoplasm

Outer Membrane

COMPOSITION OF CELL ENVELOPE

• found only in gram-negative bacteria

• function as the cell’s initial barrier to the environment

Outer Membrane

COMPOSITION OF CELL ENVELOPE

• as primary permeability barriers to hydrophilic and hydrophobic compounds and contain essential enzymes and other proteins located in the periplasmic space

Outer Membrane

COMPOSITION OF CELL ENVELOPE

• bilayered structure composed of lipopolysaccharide

Outer Membrane

COMPOSITION OF CELL ENVELOPE

• gives the surface of gram- negative bacteria a net negative charge plays a significant role in the ability of certain bacteria to cause disease

lipopolysaccharide

gives the surface of gram- negative bacteria a net negative charge

porins

• protein structures scattered throughout the lipopolysaccharide macromolecules

• number and types of porins vary with bacterial species

porins

• water-filled structures that control the passage of nutrients and other solutes, including antibiotics, through the outer membrane

porins

• influence the extent to which various substances pass through the outer membranes of different bacteria

Murein Lipoproteins

• facilitate the attachment of the outer membrane to the next internal layer in the cell envelope, the cell wall

Cell wall

COMPOSITION OF CELL ENVELOPE

• referred to as the peptidoglycan, or murein layer

• structure is composed of disaccharide- pentapeptide subunits

• gives the bacterial cell shape and strength to withstand changes in environmental osmotic pressures that would otherwise result in cell lysis

Cell wall

COMPOSITION OF CELL ENVELOPE

• protects against mechanical disruption of the cell and offers some barrier to the passage of larger substances

Cell wall

COMPOSITION OF CELL ENVELOPE

• synthesis and structure are often the primary targets for the development and design of several antimicrobial agents

N-acetyl-D-glucosamine and N-acetyl-D-muramic acid
NAG AN NAM

• alternating sugar components (moieties), with the amino acid chain linked to N-acetylmuramic acid molecules

N-acetyl-D-glucosamine and N-acetyl-D-muramic acid
NAG AN NAM

• polymers of these subunits cross-link to one another by means of peptide bridges to form peptidoglycan sheets

N-acetyl-D-glucosamine and N-acetyl-D-muramic acid
NAG AN NAM

• layers of these sheets are cross-linked with one another, forming a multilayered, cross-linked structure of considerable strength

N-acetyl-D-glucosamine and N-acetyl-D-muramic acid
NAG AN NAM

• Referred to as the murein sacculus, or sack, this peptidoglycan structure surrounds the entire cell

Staining Characteristics

Different types of cell wall structures traditionally have been categorized according to their ________________

Gram-positive

Gram-negative

Major types of Cells walls

Mycobacteria

stain gram-positive, have a modified cell wall called an ACID-FAST CELL WALL

Mycoplasmas

microorganisms that have no cell wall

Gram-Positive Cell Wall

TYPE OF CELL WALL

• composed of a very thick protective peptidoglycan (murein) layer

Gram-Positive Cell Wall

TYPE OF CELL WALL

• consists of glycan (polysaccharide) chains of alternating Nacetyl-d-glucosamine (NAG) and N-acetyl-d-muramic acid (NAM)

Peptidoglycans

many antibiotics effective against gram-positive organisms (e.g., penicillin) act by preventing synthesis of _______

Techoic Acid

TYPE OF CELL WALL

Other components of gram-positive cell wall that penetrated to the exterior of the cells

• anchored to the peptidoglycan (N-acetylmuramic acid)

• glycerol or ribitol phosphate polymers combined with various sugars, amino acids, and amino sugars

Lipoteichoic Acid

TYPE OF CELL WALL

Other components of gram-positive cell wall that penetrated to the exterior of the cells

• anchored to the PM

• linked to the next underlying layer, PM or cellular memebrane

Teichuronic acids

TYPE OF CELL WALL

Other components of gram-positive cell wall that penetrated to the exterior of the cells

• similar polymers, but the repeat units include sugar acids (eg, N-acetylmannosuronic or d-glucosuronic acid) instead of phosphoric acids

• synthesized in place of teichoic acids when phosphate is limiting

Gram-Negative Cell wall

• Inner peptidoglycan layer

• Outer membrane

TYPE OF CELL WALL

identigy the type and major layers

composed of two layers:

• ___________- much thinner than in gram-positive cell walls

• ____________- Outside the peptidoglycan layer is an additional outer membrane contains proteins, phospholipids, and lipopolysaccharide (LPS)

a. O-specific polysaccharide = Antigenic

b. Core polysaccharide"= ketodeoxyoctanoic acid (KDO)

c. Lipid A (also called endotoxin)= inner, major constituents

Lopopolysaccharide contains what 3 regions

• Vital in evading the host defenses

• Contribute to the negative charge of the bacterial surface, which stabilizes the membrane structure

• Considered as an endotoxin

LPS Functions:

Lipid A moiety

• consists of phosphorylated glucosamine disaccharide units to which are attached a number of long-chain fatty acids

• responsible for producing fever and shock conditions in patients infected with gram-negative bacteria

• Acts as a barrier to hydrophobic compounds and harmful substances

• Acts as a sieve, allowing water-soluble molecules to enter through protein-lined channels called porins

• Provides attachment sites that enhance attachment to host cells

• Strong negative charge is an important factor in evading phagocytosis

• Acts as a barriers to toxic substances that prevents movement inside the cell

Outer membrane function

• Gram positive-Thick (multilayered

• Gram Negative- Thin (Bilayered/Trilayered)

CHARACTERISTICS
Peptidoglycan Layer

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Present in many

• Gram Negative- Absent

CHARACTERISTICS
Teichoic Acids

• Gram positive-__________

• Gram Negative- ________

• Gram positive- Absent

• Gram Negative- Present

CHARACTERISTICS
Periplasmic Space

• Gram positive-__________

• Gram Negative- ________

• Gram positive- Absent

• Gram Negative- Present

CHARACTERISTICS
Outer Membrane

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Virtually none

• Gram Negative- High

CHARACTERISTICS
LPS content

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Low

• Gram Negative- High

CHARACTERISTICS
Lipid and LPP

• Gram positive-__________

• Gram Negative- ________

• Gram positive- 2 RIngs in Basal body

• Gram Negative- 4 RIngs in Basal body

CHARACTERISTICS
Flagellar structure

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Exotoxins

• Gram Negative- Endotoxins and Exotoxins

CHARACTERISTICS
Toxins Produced

• Gram positive-__________

• Gram Negative- ________

• Gram positive-High

• Gram Negative- Low

CHARACTERISTICS
Resistance to Physical Disruption

• Gram positive-__________

• Gram Negative- ________

• Gram positive-High

• Gram Negative-Low

CHARACTERISTICS
Cell disruptionby lysozymes

• Gram positive-__________

• Gram Negative- ________

• Gram positive- High

• Gram Negative- Low

CHARACTERISTICS
Susceptibility of Pen and Sulfonamide

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Low

• Gram Negative- High

CHARACTERISTICS
Susceptibility to Step, Chroram and Tetra

• Gram positive-__________

• Gram Negative- ________

• Gram positive- High

• Gram Negative- Low

CHARACTERISTICS
Inhibitions by Basic Dyes

• Gram positive-__________

• Gram Negative- ________

• Gram positive-Low

• Gram Negative- High

CHARACTERISTICS
Resistance to Anionic Detergents

• Gram positive-__________

• Gram Negative- ________

• Gram positive- High

• Gram Negative- Low

CHARACTERISTICS
Resistance to Sodium azide

• Gram positive-__________

• Gram Negative- ________

• Gram positive-High

• Gram Negative- Low

CHARACTERISTICS
Resistance to Drying

• Gram positive-__________

• Gram Negative- ________

Gram positive

• Spherical

• rod-shape

• filamentous

Gram Negative

• Spaherical

• oval

• straight or curved

• helical or filamentous

PROPERTIES
Shape

• Gram positive-__________

• Gram Negative- ________

Gram positive

• Chemoorganoheterotrophic

Gram Negative

• Phototrophic

• chemolitoautotrophic

• Chemoorganoheterotrophic

PROPERTIES
Metebolism

• Gram positive-__________

• Gram Negative- ________

Gram positive

• Present in some groups

Gram Negative

• Absent

PROPERTIES
Endospore

• Gram positive-__________

• Gram Negative- ________

Gram positive

• Binary Fission

Gram Negative

• Binary FIssion

PROPERTIES
Reproduction

• Gram positive-__________

• Gram Negative- ________

Acid-Fast Cell Wall

TYPE OF CELL WALL

• have a gram-positive cell wall structure

• contain a waxy layer of glycolipids and fatty acids (mycolic acid) bound to the exterior of the cell wall

• More than 60% of the cell wall is lipid

Mycolic acid

TYPE OF CELL WALL

Part of Acid-fast cell wal

• major lipid component

• strong “hydrophobic” molecule that forms a lipid shell around the organism and affects its permeability

• makes Mycobacterium spp. difficult to stain with the Gram stai

Mycobacterium and Nocardia

• stain a faint blue (gram-positive) color

• best stained with an acid-fast stain

Absence of Cell Wall

TYPE OF CELL WALL

• lack a cell wall and contain STEROLS in their cell membranes

• lack the rigidity of the cell wall

• seen in various shapes microscopically

Mycoplasma

Ureaplasma

Example of BActeria with Absent Cell wall

Serum
Sugar

*Gram-positive and gram-negative cells can lose their cell walls and grow as L-forms in media supplemented with ____ or ____ to prevent osmotic rupture of the cell membrane

Periplasmic Space

COMPOSITION OF CELL ENVELOPE

• typically found only in gram-negative bacteria

Periplasmic Space

COMPOSITION OF CELL ENVELOPE

• bounded by the internal surface of the outer membrane and the external surface of the cellular membrane encompassing the thin peptidoglycan layer

Periplasmic Space

COMPOSITION OF CELL ENVELOPE

• contains the murein layer, consists gellike matrix containing nutrient-binding proteins that assist in the capture of nutrients from the environment

Periplasmic Space

COMPOSITION OF CELL ENVELOPE

• contains several enzymes involved in the degradation of macromolecules and detoxification of environmental solutes, including antibiotics that enter through the outer membrane

Cytoplasmic (Inner) Membrane

COMPOSITION OF CELL ENVELOPE

• present in both gram-positive and gramnegative bacteria and is the deepest layer of the cell envelope

Cytoplasmic (Inner) Membrane

COMPOSITION OF CELL ENVELOPE

• consist of phospholipid bilayer, various proteins (70%), including a number of enzymes vital to cellular metabolism

Cytoplasmic (Inner) Membrane

COMPOSITION OF CELL ENVELOPE

• serves as an additional osmotic barrier

• absence of sterols

Mycoplasma

incorporate sterols (e.g., cholesterol), into their membranes when growing in sterol-containing media

• Transport of solutes into and out of the cell

• Housing of enzymes involved in outer membrane synthesis, cell wall synthesis, and the assembly and secretion of extracytoplasmic and extracellular substances

• Generation of chemical energy (i.e., ATP)

• Cell motility

• Mediation of chromosomal segregation during replication

• Housing of molecular sensors that monitor chemical and physical changes in the environment

• Electron transport and oxidative phosphorylation in aerobic species

• Excretion of hydrolytic exoenzyme

FUNCTION OF CYTOPLASMIC MEMBRANE

Passive Tranport

PERMEABILITY AND TRANSPORT

• relies on diffusion, uses no energy, and operates only when the solute is at higher concentration outside than inside the cell

Simple Diffusion

PERMEABILITY AND TRANSPORT

• Type of Passive Tranports that accounts for the entry of very few nutrients, including dissolved oxygen, carbon dioxide, and water itself

Facilitated Diffusion

PERMEABILITY AND TRANSPORT

• Type of Passive Tranports that is selective and uses no energy so the solute never achieves an internal concentration greater than what exists outside the cell (e.g., Glycerol)

Channel Proteins

PERMEABILITY AND TRANSPORT

• Type of Passive Tranports that form selective channels that facilitate the passage of specific molecules

Active Tranport

PERMEABILITY AND TRANSPORT

• the other type of transport other than passive transport

Ion-coupled transport

PERMEABILITY AND TRANSPORT

• Type of Active Transport that move a molecule across the cell membrane at the expense of a previously established ion gradient such as protonmotive or sodiummotive force

• particularly common in aerobic organisms, which have an easier time generating an ion-motive force than do anaerobes

Uniport

PERMEABILITY AND TRANSPORT

• Type of Active Ion-coupled Transport that catalyze the transport of a substrate independent of any coupled ion

Symport

PERMEABILITY AND TRANSPORT

• Type of Active Ion-coupled Transport that simultaneous transport of two substrates in the same direction by a single carrier

Antiport

PERMEABILITY AND TRANSPORT

• Type of Active Ion-coupled Transport that simultaneous transport of two likecharged compounds in opposite directions by a common carrier (40% of the substrates transported by E coli)

ABC Transport

PERMEABILITY AND TRANSPORT

• TYpe of active transport that uses ATP directly to transport solutes into the cell

Gram-negative

PERMEABILITY AND TRANSPORT

• Type of gram bacteria that uses active ABC tranport that transport of many nutrients is facilitated by specific binding proteins located in the periplasmic space

Gram-positive

PERMEABILITY AND TRANSPORT

• Type of gram bacteria that uses active ABC tranport that used binding proteins are attached to the outed surface of the cell membrane

Group Translocation

PERMEABILITY ANF TRANSPORT

• vectorial metabolism

• not active transport because no concentration gradient is involved

• Allows bacteria to use their energy resources efficiently by coupling transport with metabolism

Siderophores

PERMEABILITY ANF TRANSPORT

• Special tranport processes where compounds that chelate Fe and promote its transport as a soluble complex

Transferrin
Lactofrrin

Some pathogenic bacteria use specific receptors that bind host ______ and _______ (as well as other ironcontaining host proteins)

Ribosome

CYTOPLASMIC STRUCTURE

• site of protein biosynthesis and gives the cytoplasm a granular structure

• Consist of RNA and proteins 70S in size and separates into two subunits, 50S and 30S

Streptomycin and Gentamac

attach to the 30S subunit and interfere with protein synthesis

Erythromycin and Chloramphenicol

interfere with protein synthesis by attaching to the 50S subunit

Genome

CYTOPLASMIC STRUCTURE

• Consist of a single, circular chromosome

• lacks nuclear membrane and mitotic apparatus

• Appears as diffused nucleoid or chromatin body that is attached to a mesosome (sac-like structure)

Nucleoid = FUlgen positive

Under Genome:

Consists of a single continuous circular molecule ranging in size from 0.58 to almost 10 million base pair

Borrelia burgdorferi

Streptomyces coelicolor

Bacteria with Linear Chromosomes and an exception to the rule of cirular chromosome

Vibrio cholera

Brucella melitensis

Bacteria that have dissimilar chromosomes

Plasmid

CYTOPLASMIC STRUCTURE

• extrachromosomal, double-stranded element of DNA that is associated with virulence

Plasmid

CYTOPLASMIC STRUCTURE

• Located in the cytoplasm and serve as a site for the genes to code for antibiotic resistance and toxin production

• Not essential for bacterial growth so a bacterial cell may or may not contain it

Plasmid

CYTOPLASMIC STRUCTURE

• Sometimes disappears during cell division and it can make bacteria (mostly Gram-neg) pathogenic

Large Plasmid

CYTOPLASMIC STRUCTURE

• kind of plasmid that is responsible for the production of B-lactamase that provide resistance to B-lactam antibiotics (penicillin and oxacillin)

Small Plasmid

CYTOPLASMIC STRUCTURE

• kind of plasmid that is resistant to tetracyclines and chloramphenicol

Inclusions Bodies

CYTOPLASMIC STRUCTURE

• Serve as the energy source or food reserve of the bacteria or as a reservoir of structural bulding blocks