Bacterial morphology metabolism and growth
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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

Cell

  • Fundemental unit of living things

    (smallest bacterium-largest plants-animals)


Bacteria

Bacteria

  • 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

    Diversity!


Most bacterial cells

Most bacterial cells

  • Approximately 1 micrometer in diameter

  • Visible by light microscope

  • Resolution: 0.2 micrometer


Microscopes

Microscopes

  • Light:

    • Bright-field

    • Dark-field (Treponema pallidum-Syphilis_Frengi)

    • Fluorescence

    • Phase contrast (details of the living cell)

  • Electron


Staining

Staining

  • Simple

  • Differential: Gram and Acid-fast stain

    Gram-stain: cell wall

    Acid fast stain: Mycobacterium

  • Negative stain: Indian ink

    (capsule)

  • 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.


Cells

Cells

  • Eukaryotic (Greek for true nucleus)

  • Prokaryotic (Greek for primitive nucleus)


Eucaryotes

Eucaryotes

  • Animals

  • Plants

  • Fungi


Procaryotes

Procaryotes

  • Bacteria

  • Blue-green algae


Major characteristics of eucaryotic and prokaryotic cell

Major characteristics of Eucaryotic and prokaryotic cell

EucaryoteProkaryote

  • Size>5 μm0,5-3 μm

  • Nuclear

    structure :

    Nucleus classic membrane no membrane

    Chromosomes

    strands of DNA single circular DNA

    diploid genome haploid genome


Major characteristics of eucaryotic and prokaryotic cell1

Major characteristics of Eucaryotic and prokaryotic cell

EucaryoteProkaryote

  • Cytoplasmic

    Structures

    Mitokondria+-

    Golgi bodies+-

    Endoplasmic

    reticulum+-

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

    Cytoplasmic

    membranewith sterolsno sterol


Major characteristics of eucaryotic and prokaryotic cell2

Major characteristics of Eucaryotic and prokaryotic cell

EucaryoteProkaryote

  • Cell wall -/composed of kitincomplex structure

    (protein, lipits and peptidoglycans)

  • Reproduction sexual and asexualasexual (binary

    fission)

  • Movement complex flagellumsimple flagellum

    (If present)(If present)

  • Respiration via mitokondriavia cytoplasmic membrane


Bacteria1

Bacteria

  • 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.


Differences

Differences

  • Between Eukaryotes and prokaryotes


Differences between prokaryotes

Differences between Prokaryotes

  • Bacteria differ:

    -morphology (size, shape, stainig characteristics)

    -metabolic

    -antigenic and

    -genetic characteristics


Bacterial morphology metabolism and growth

Size

  • They are diffucult to differentiate by size


Shape

Shape

  • 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)

Rod-shaped

Spiral

Spiral or spirillum

Helix or spirochete


Bacterial arrangement

Bacterial arrangement

Diplococcus

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


Cytoplasm

Cytoplasm

  • 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


Plasmids

Plasmids

  • 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


Ribosomes

Ribosomes

  • 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


Mesosome

Mesosome

  • 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


Peptidoglycan

Peptidoglycan

  • During infection

  • İnterferes with phagocytosis

  • Stimulates lymphoctes

  • Pyrogenic activity (induces fever)


Peptidoglycan1

Peptidoglycan

  • 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


Protoplast

Protoplast

  • 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


Lipopolysaccaride

Lipopolysaccaride

  • 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


Capsules

Capsules

  • 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.


Capsule

Capsule

  • Polypeptide capsule:

  • Bacillus anthracis (polyglutamic acid)


Capsule1

Capsule

  • Hard to be seen by microscopy

  • Negative staining: Indian ink


Capsule2

Capsule

  • Unnecessary for growth

  • Very important for survival


Capsule3

Capsule

  • 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


Flagella

Flagella

  • 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


Mycobacteria

Mycobacteria

  • 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.


Mycoplasmas

Mycoplasmas

  • 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-acetylglucosamine

    N-acetylmuramic acid

  • Cross-linked by peptides


Cell wall synthesis

Cell wall synthesis

  • Cross-linking reaction is catalyzed by:

    -membrane bound transpeptidases

    -DD-carboxypeptidases-

    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)


Lipopolysaccaride1

Lipopolysaccaride

  • Lipid A

  • Core polysaccaride

  • O antigen


Lipoppolysaccaride

Lipoppolysaccaride

  • 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


Spores

Spores

  • Resistant to harsh conditions

  • (loss of nutritional requirement, dessication, intense heat, radiation and attack by most enzymes and chemical agents)


Spores1

Spores

  • 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

    ‘drumstick’

  • 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.


Spore

Spore

  • Dehydrated

  • Multishelled structure

  • A complete copy of chromosome

  • Minimum concentration of proteins and

    Ribosomes + High concentration of calcium bound dipicolinic acid


Spore1

Spore

  • Outside the core:

    -inner membrane

    -spore wall

    -cortex

    -outher membrane

    -keratin-like protein coat

    -exosporium


Sporulation

Sporulation

  • 6-8 hours


Germination

Germination

  • 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:

    -aminoacids

    -carbohydrates

    -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

Heat

  • Cardinal temperatures:

    -minimum temperature

    -optimum temperature

    -maximum temperature


Temperature

Temperature

  • Psychrophiles

  • Mesophiles

  • Thermophiles

  • Hyperthermophiles


Bacterial morphology metabolism and growth

ph

  • 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)


Methabolism

Methabolism

  • 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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