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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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Bacterial morphology, metabolism and growth

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Bacterial morphology metabolism and growth

Bacterial morphology, metabolism and growth

Dr Ömer Küçükbasmacı

Bacterial morphology metabolism and growth


  • 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


  • Size>5 μm0,5-3 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


  • Cytoplasmic



    Golgi bodies+-



    Ribosomes80S(60S+40S) 70S(50S+30S)


    membranewith sterolsno sterol

Major characteristics of eucaryotic and prokaryotic cell2

Major characteristics of Eucaryotic and prokaryotic cell


  • Cell wall -/composed of kitincomplex structure

    (protein, lipits and peptidoglycans)

  • Reproduction sexual and asexualasexual (binary


  • Movement complex flagellumsimple flagellum

    (If present)(If present)

  • Respiration via mitokondriavia 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

Bacterial morphology metabolism and growth


  • 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

Treponema by dark field microscopy

Treponema by dark-field microscopy

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.

Bacterial morphology metabolism and growth

  • Corynebacterium

  • 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

Bacterial morphology metabolism and growth

  • Chemotrophs:

    derive energy from inorganic material

  • Chemoorganotrophs:

    Most bacterial

Bacterial morphology metabolism and growth


  • Cardinal temperatures:

    -minimum temperature

    -optimum temperature

    -maximum temperature



  • Psychrophiles

  • Mesophiles

  • Thermophiles

  • Hyperthermophiles

Bacterial morphology metabolism and growth


  • 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

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