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Bacterial morphology, metabolism and growth. Dr Ömer Küçükbasmacı. Cell. Fundemental unit of living things (smallest bacterium-largest plants-animals). Bacteria. The smallest cells Visible only with the aid of a microscope The smallest bacteria: Chlamydia and Rickettsia-0.1-0.2 micrometer

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  • Fundemental unit of living things

(smallest bacterium-largest plants-animals)

  • The smallest cells
  • Visible only with the aid of a microscope
  • The smallest bacteria: Chlamydia and Rickettsia-0.1-0.2 micrometer
  • Larger bacteria: many microns in length
a newly described species
A newly described species
  • Hundred of times larger than the average bacterial cell
  • Is visible to the naked eye


most bacterial cells
Most bacterial cells
  • Approximately 1 micrometer in diameter
  • Visible by light microscope
  • Resolution: 0.2 micrometer
  • Light:
    • Bright-field
    • Dark-field (Treponema pallidum-Syphilis_Frengi)
    • Fluorescence
    • Phase contrast (details of the living cell)
  • Electron
  • Simple
  • Differential: Gram and Acid-fast stain

Gram-stain: cell wall

Acid fast stain: Mycobacterium

  • Negative stain: Indian ink


  • Special staining
animal and plant cells
Animal and plant cells
  • Much larger
  • Ranging from 7micrometer (red blood cells)
  • To several feet (certain nerve cell)
each cell
Each cell
  • Genetic basis for reproduction (DNA genome)
  • Biochemical machinery (genetic information is transcribed in mRNA and mRNA translated in proteins)
  • The machinery for energy production and biosynthesis
  • This is all packaged by a membrane.
each cell1
Each cell
  • Replicates by cell division.
  • Eukaryotic (Greek for true nucleus)
  • Prokaryotic (Greek for primitive nucleus)
  • Animals
  • Plants
  • Fungi
  • Bacteria
  • Blue-green algae
major characteristics of eucaryotic and prokaryotic cell
Major characteristics of Eucaryotic and prokaryotic cell

Eucaryote Prokaryote

  • Size >5 μm 0,5-3 μm
  • Nuclear

structure :

Nucleus classic membrane no membrane


strands of DNA single circular DNA

diploid genome haploid genome

major characteristics of eucaryotic and prokaryotic cell1
Major characteristics of Eucaryotic and prokaryotic cell

Eucaryote Prokaryote

  • Cytoplasmic


Mitokondria + -

Golgi bodies + -


reticulum + -

Ribosomes 80S(60S+40S) 70S(50S+30S)


membrane with sterols no sterol

major characteristics of eucaryotic and prokaryotic cell2
Major characteristics of Eucaryotic and prokaryotic cell

Eucaryote Prokaryote

  • Cell wall -/composed of kitin complex structure

(protein, lipits and peptidoglycans)

  • Reproduction sexual and asexual asexual (binary


  • Movement complex flagellum simple flagellum

(If present) (If present)

  • Respiration via mitokondria via cytoplasmic membrane
  • Lack nucleus membrane and membrane bound organelles
  • A smaller ribosome
  • Peptidoglycan cell wall which protects it from environtment with low osmotic pressure, at temperature extremes (both hot and cold), dryness and with very dilute and diverse energy sources.
  • They have evolved their structures and functions to adopt these conditions.
  • Between Eukaryotes and prokaryotes
differences between prokaryotes
Differences between Prokaryotes
  • Bacteria differ:

-morphology (size, shape, stainig characteristics)


-antigenic and

-genetic characteristics

  • They are diffucult to differentiate by size
  • Spherical: coccus (Staphyloccus)
  • Rod-shaped: bacillus (Escherichia)
  • Snakelike: spirillum (Treponema)
  • Branched filamentous (Nocardia and Actinomyces)

( Clusters: diplococcus (Neisseria)

chains (Streptococcus)

grapelike (Staphylococcus) )

bacterial shape
Bacterial shape

Sperical (coccus)



Spiral or spirillum

Helix or spirochete

bacterial arrangement
Bacterial arrangement


Chains: streptococcus

Clusters: staphylococcus

Packets of eight:sarcina

gram stain
Gram stain
  • Two major classes of bacteria are distinguished:
  • Gram-positive and
  • Gram-negative bacteria
  • Except:
  • Mycobacteria (waxy outer shell , distinguished by acid fast stain)
  • Mycoplasmas(no peptidoglycan)
bacterial ultrastructure
Bacterial Ultrastructure
  • Internal structure
  • External structure
  • Gram-positive and gram-negative bacteria have

-Similar internal structure

-But different external structure

  • DNA chromosome
  • mRNA
  • Ribosomes
  • Proteins
  • Metabolites
bacterial chromosome
Bacterial chromosome
  • Unlike eukaryotes
  • A single
  • Double stranded circle
  • Not in a membrane bound nucleus
  • In a discrete area called nucleoid
bacterial chromosome1
Bacterial chromosome
  • Unlike eukaryotes
  • No histons
  • Smaller
  • Circular
  • Extrachromosomal DNAs
  • Not usually essential for cellular survival
  • Most commonly found in gram-negative bacteria
  • Often provide a selective advantage: resistance to antibiotics
lack of a nuclear membrane
Lack of a nuclear membrane
  • Simplifies the requirements and
  • Control mechanisms for the synthesis of proteins
  • Unlike the eukaryotic 80S(40S+60S)ribosome
  • Bacterial 70S chromosome (30+50S)
  • Proteins and RNA of the ribosome are significantly different
  • Major targets for antibacterial drugs
cytoplasmic membrane
Cytoplasmic membrane
  • Lipid bilayer
  • Similar to eukaryotic membranes
  • But no sterols (cholesterol)

Exception: Mycoplasmas

cytoplasmic membrane1
Cytoplasmic membrane
  • Responsible for many functions
  • Attributable to organelles in eukaryotes:

-electron transport

-energy production (mitokondria in eukaryotes)

cytoplasmic membrane2
Cytoplasmic membrane
  • Transport proteins: uptake of metabolites release of other substances
  • Ion pumps: to maintain a membrane potential
  • Enzymes
  • A coiled cytoplasmic membrane
  • An anchor to bind and pull apart daughter chromosomes during cell division.
cell wall
Cell wall
  • Distinguishes gram-positive and gram-negative bacteria
the cytoplasmic membrane in most prokaryotes surrounded by
The cytoplasmic membrane in most prokaryotes surrounded by
  • Rigid peptidoglycan (murein) layer
  • Except: Archaebacteria (pseudoglycan and pseudomurein) and mycoplasmas (no cell wall)
  • Peptidoglycan provides rigidity and determines the shape of a bacteria
  • Gram-negative bacteria. + outer membranes
gram positive bacteria
Gram positive bacteria
  • Thick multilayered cell wall
  • Consisting mainly of peptidoglycan
gram positive bacteria1
Gram positive bacteria
  • Peptidoglycan
  • Sufficiently porous(allows diffusion of metabolites to the plasma membrane)
  • Essential for structure, replication, for survival
  • During infection
  • İnterferes with phagocytosis
  • Stimulates lymphoctes
  • Pyrogenic activity (induces fever)
  • Degraded by lysozyme
  • Enzyme in human tears, mucus (produced by bacteria and other organisms)
  • Degrades the glycan backbone of the peptidoglycan which protects it from osmotic pressure changes
  • Removal of cell wall with lysozyme
  • Lysis unless it is osmotically stabilized
gram positive cell wall
Gram-positive cell wall
  • Peptidoglycan +
  • Teicoic acid
  • Lipoteichoic acid
  • Complex polisaccarides (C polysaccharides)
  • M protein of streptococci
  • R protein of staphylococci
gram positive bacteria2
Gram-positive bacteria
  • Teicoic acid : covalently linked to peptidoglycan
  • Lipoteichoic acid : anchored in the cytoplasmic membrane
  • Common surface antigens
  • Distinguish bacterial serotypes
  • Promote attachment to other bacteria and to spesific receptors on mammalian cell surfaces (adherence)
gram positive bacteria3
Gram positive-bacteria
  • Teicoic acid: important virulance factors
  • Lipoteicoic acid are shed into media and host
  • Although weaker
  • Can initiate endotoxic-like activities.
gram negative bacteria
Gram-negative bacteria
  • Cell wall is more complex
  • Both structurally and chemically
gram negative bacteria1
Gram-negative bacteria
  • Two layers external to the cytoplasmic membrane:
  • -Thin peptidoglycan layer
  • -Outer mebrane (unique to gram-negative bacteria)
  • No teicoic acid and lipoteicoic acid
  • +periplasmic space
periplasmic space
Periplasmic space
  • The area between the external surface of rhe cytoplasmic membrane and the internal surface of the outher membrane
periplasmic space1
Periplasmic space
  • A variety of hydrolytic enzymes
  • Breakdown of large macromolecules for metabolism
  • Lytic virulence factors ( collagenases, hyalurodidases, proteases, beta-lactamases)
  • Components of sugar transport system
  • Binding proteins for the uptake of different metabolites and of a chemotaxis system
outer membranes
Outer membranes
  • Unique to gram-negative-bacteria
  • Maintains the bacterial structure
  • Permeability barrier to large molecules and hydrophobic molecules
  • Provides protection from adverse environmental conditions (For Enterobactericeae from digestive system of the host)
outer membranes1
Outer membranes
  • Asymetric bilayer
  • The inner leaflet: phospholipits normally found in bacterial membranes
  • Outer leaflet: amphipathic molecule( having both hydrophobic and hydrophilic ends) contains Lipopolysaccaride (LPS)
outer membranes2
Outer membranes
  • LPS molecules are only found in the outer leaflet
  • Endotoxin (Lipid A+polysaccharide-O antigen, antigenic variety is great)
  • Powerful stimulator of immune responses
  • Causes fever and shock Shwartzman reaction (disseminated intravascular coagulation) follows the release of large amounts of endotoxin.
outer membrane proteins
Outer membrane proteins
  • Porins: transmembrane proteins they form pores allow diffusion of hydrophilic molecules
  • Structural proteins and receptor molecules for bacteriophages
disruption of the outher membrane
Disruption of the outher membrane
  • Weakens the bacteria
  • +lysozyme
  • Spheroplasts (osmotically sensitive) are formed.
external structures
External structures
  • Capsule
  • Pili
  • Flagellum
  • Proteins
  • Some bacteria (gram-positive and gram-negative)
  • Loose polysaccaride or proteinlayer
  • Slime layer: loosely adherent and nonuniform in density and thickness
  • Glycocalyx: capsule and slime layer are also called.
  • Polypeptide capsule:
  • Bacillus anthracis (polyglutamic acid)
  • Hard to be seen by microscopy
  • Negative staining: Indian ink
  • Unnecessary for growth
  • Very important for survival
  • Poorly antigenic
  • Antiphagocytic and a major virulence factor (Streptococcus pneumoniae)
  • Barrier to toxic hydrophobic molecules such as detergents
  • Promote adherence (Streptococcus mutants: stick the tooth)
quellung reaction
Quellung reaction
  • For vizualizing the capsule
  • Using antibodies
  • The capsule is swollen
flagella kirpik
Flagella (Kirpik)
  • Motility
  • Protein (flagellin)
  • Antigenic and strain determinants
  • Anchored in membranes through a hook and basal body
  • One or several
  • Monotrichous
  • Polar: Pseudomonas aeruginosa
  • Peritrichous :Escherichia coli
  • Lophotrichous
fimbriae pili
Fimbriae (Pili)
  • Protein(pilin)
  • Different from flagella: smaller in diameter and not coiled in structure.
  • Promote adherence to other bacteria or to th host (adhesins, lectins, evasins, aggresins)
fimbriae pili1
Fimbriae (Pili)
  • Fimbriae are important virulance factors as an adhesin in E. Coli (urinary tract), Neisseria gonorrhoeae
  • The tips of fimbriae may contain proteins-lectins that bind to spesific sugars-mannose
fimbriae pili2
Fimbriae (Pili)
  • F pili (Sex)
  • Promote transfer of large segments of bacterial chromosome between bacteria
  • Encoded by a F plasmid.
bacterial exceptions
Bacterial exceptions
  • Mycobacteria
  • Corynebacterium
  • Nocardia
  • Mycoplasmas
  • Peptidoglycan (slightly different)
  • Waxlikelipit coat of mycolic acid
  • Cord factor
  • Wax D
  • Sulfolipids
  • Acid-fast staining
  • The coat responsible for virulence and antiphagocytic.
  • Nocardia

Produce mycolic acid lipids.

  • No peptidoglycan cell wall
structure of bacterial cell wall
Structure of Bacterial Cell Wall
  • The components are large structures
  • They are made up of polymers of subunits
  • Synthesis of it occurs outside the bacteria
peptidoglycan mucopeptide murein
Peptidoglycan(Mucopeptide, Murein)
  • Linear polysaccaride chain:

-repeating disaccarides:


N-acetylmuramic acid

  • Cross-linked by peptides
cell wall synthesis
Cell wall synthesis
  • Cross-linking reaction is catalyzed by:

-membrane bound transpeptidases


penicillin-binding proteins (PBPs)

cell wall synthesis1
Cell wall synthesis
  • Penicillin-binding proteins (PBPs):

-remove extra terminal D-alanines

-These terminal D-alanines limit the extent of cross-linking

-They are targets for penicillin and beta-lactam antibiotics

cell wall1
Cell wall
  • Peptidoglycan is constantly being synthesized and degraded.
  • Autolysins such as lysozyme are important for determining the shape of bacteria.
cell wall2
Cell wall
  • During starvation:

-New peptidoglycan synthesis does not occur

-Peptidoglycan is weakened

-Gram-staining property changes

(old cultures)

biosynthesis of peptidoglycan
Biosynthesis of peptidoglycan
  • Unique to bacterial cells
  • İnhibited with no adverse effect of human cells
  • An important target for antibiotics

(selective toxicity)

  • Lipid A
  • Core polysaccaride
  • O antigen
  • Lipid A:

basic component

essential for bacterial viability

endotoxin activity

  • O antigen: antigenic part (serotypes)
inclusion granules
Inclusion granules
  • Storage of energy
  • Poly-beta-hydroxybutyric acid (PHB)
  • Glycogen
  • Polyphosphate
inclusion granules1
Inclusion granules
  • Polymetaphosphate: Corynebacterium

-Babes-Ernst bodies

  • Resistant to harsh conditions
  • (loss of nutritional requirement, dessication, intense heat, radiation and attack by most enzymes and chemical agents)
  • Exist for centuries
  • Diffucult to decontaminate with standart disinfectants
spores formers
Spores formers:
  • Some gram-positive
  • Never gram-negative
spore formers
Spore formers
  • Bacillus
  • Clostridium
kinds of spores
Kinds of spores
  • Endospore: Bacillus subtilis
  • Terminal endospore: Clostridium tetani


  • Subterminal: Clostridium botulinum
under harsh conditions
Under harsh conditions
  • Vegetative state is converted to dormant state (spore)
localisation of the spore within a cell
Localisation of the spore within a cell
  • Characteristic of bacteria
  • Can assist in identification of the bacterium.
  • Dehydrated
  • Multishelled structure
  • A complete copy of chromosome
  • Minimum concentration of proteins and

Ribosomes + High concentration of calcium bound dipicolinic acid

  • Outside the core:

-inner membrane

-spore wall


-outher membrane

-keratin-like protein coat


  • 6-8 hours
  • Spor__vegetative state:

disruption of the outher coat

by mechanical stress, pH, heat or

another stressor

It takes about 90 minutes

bacterial metabolism
Bacterial metabolism
  • Bacterial growth:

-a source of energy

-raw materials

*To build the proteins, structures and membranes

*That make up the structure and biochemical machines of the cell

bacterial metabolism1
Bacterial metabolism
  • Bacteria should obtain or synthesize:



-lipids as building blocks of the cell

the minimum requirement for growth
The minimum requirement for growth
  • Carbon
  • Nitrogen
  • Energy source
  • Water
  • Various ions

derive energy from inorganic material

  • Chemoorganotrophs:

Most bacterial

  • Cardinal temperatures:

-minimum temperature

-optimum temperature

-maximum temperature

  • Psychrophiles
  • Mesophiles
  • Thermophiles
  • Hyperthermophiles
  • Acidophiles: Below pH 5 (many fungi)
  • Alkaliphiles: Above pH 9 (Vibrio)
  • Neutral pH: most pathogens
oxygen requirement
Oxygen requirement
  • Obligate anaerobes :

Clostridium perfringens

  • Obligate aerobes
  • Facultative anaerobes
  • Microaerophilic
incubation for growth
Incubation for growth
  • Aerobic
  • Anaerobic
  • Capneic (%5 Carbon dioxide)
  • Catabolism: substrate breakdown and conversation into usable energy
  • Anabolism: synthesis of cellular constituents (cell wall, proteins,fatty acids, nucleic acids
bacterial growth
Bacterial growth
  • Bacterial replication
  • Two equivalent daughter cells
  • Binary fission

(Escherichia coli: 20 minutes

Mycobacterium much slower: 12-24h)

bacterial growth curve
Bacterial growth curve
  • Lag phase
  • Exponential phase
  • Stationary phase
  • Death phase