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Characteristics of microbes

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Title: Characteristics of microbes


1
Characteristics of microbes
Major groups of microorganisms
  • VirusesNot cells contain either RNA or DNA in
    envelope can only multiply in living cells.
  • BacteriaUnicellular procaryotic rigid cell
    wall absorb nutrients. Archaebacteria
    eubacteria
  • Archaebacteria
  • Non-peptidoglycan cell walls
  • Have unusual metabolic capabilities.
  • Live in extreme environments.
  • Methanogens, halophiles and thermoacidophiles.

2
Characteristics of microbes
Major groups of microorganisms 2
  • FungiEither uni- or multicellular eucaryotic
    rigid cell walls absorb nutrients.
  • ProtozoaSingle celled eucaryotic lack rigid
    cell wall ingest food.
  • AlgaeEither uni- or multicellular eucaryotic
    rigid cell walls chlorophyll absorb nutrients.

3
Structure/function of eubacteria
Size, shape and arrangement
Diameter Length Ave. 0.5 - 1 ?mup to 500 ?m 1.1 - 1.5 ?m wide 2.0 - 6.0 ?m long (E. coli )
Spherical Rods Spiral coccus (sing.) cocci (pl.) meaning berries.bacillus (sing.) bacillus (pl.) meaning little staffs. spirullum (sing.) spirilla (pl.)
Pleomorphy variety of shapes in a species
4
Structure/function of eubacteria
Size, shape and arrangement 2
5
Structure/function of eubacteria
Size, shape and arrangement 3
6
Structure/function of eubacteria
Ultrastructure
Cell wall
7
Structure/function of eubacteria
Ultrastructure 2
  • Cell wall

Rigid, strong structure gives and maintains
shape.10 - 40 of dry weight of the
cell.Usually essential for cell division.
A barrier to some substances.Not homogeneous
structures depending on species, layered with
different substances which have different
thicknesses.
8
Structure/function of eubacteria
Ultrastructure 3
  • Peptidoglycan (a.k.a. murein)

Shape determining part of the wall.Insoluble,
porous polymer of great strength and rigidity.
Comprises N-acetylglucosamine, N-acetylmuramic
acid and tetrapeptides.Peptidoglycan chains are
cross-linked at the tetrapeptide units.Autolysin
opens the network for addition of new polymer.
9
Structure/function of eubacteria
Ultrastructure 3
10
Structure/function of eubacteria
Ultrastructure 4
There are 2 types of cells wall in eubacteria
  • Gram stain differently
  • Differences in the layering and presence of outer
    membrane (in G -)explains the difference in Gram
    reaction and pathogencity.

11
Structure/function of eubacteria
Ultrastructure 5
The G() cell wall
  • Peptidoglycan content ? 50cf. G(-) ? 10?
    walls of G() bacteria appear thicker.
  • Contains techoic acid (may aid in the transport
    of cations).

12
Structure/function of eubacteria
Ultrastructure 5
The G(-) cell wall
  • More complex has outer membrane covering a thin
    layer of peptidoglycan.
  • Outer membrane Contains lipolysaccharides (lipid
    portion causes toxic effects in infected
    animals).

13
Structure/function of eubacteria
Ultrastructure 5
Cytoplasmic membrane
  • Composition Phospholipids 20 - 30
    Proteins 50 - 70

14
Structure/function of eubacteria
Ultrastructure 6
Cytoplasmic membrane 2
  • A site of specific enzyme activity, transport of
    molecules in and out of the cell, and
    invaginations participate in cell metabolism and
    replication.
  • Some processes essential to the cell are located
    here.

A barrier to most water-soluble molecules, and
is more selective than the cell wall.
Permeases transport small molecules into the
cell.
Also contains various enzymes for energy
production and synthesis of cell wall.
  • Photosynthetic bacteria or those with metabolisms
    based on gas exchange have elaborate
    intracellular extensions of the cytoplasmic
    membrane.This infolding increases the area for
    light pigments or gas exchange.

15
Structure/function of eubacteria
Ultrastructure
Cytoplasmic area
16
Structure/function of eubacteria
Ultrastructure 6
Cytoplasmic area
  • 80 water with nucleic acids, proteins,
    carbohydrates, lipids, inorganic ions, many
    low-molecular weight compounds and particles with
    various functions.
  • Ribosomes. Free in cytoplasm, not membrane-bound.
  • Cell inclusions (insoluble chemical substances
    accumulated) e.g. metachromatic granules (a.k.a
    volutin a reserve of inorganic
    phosphate).Lipids e.g. poly-?-hydroxybutyrate
    reserve carbon and energy source.Sulfur
    H2S-oxidizing bacteria.Polysaccharides e.g.
    glycogen and starch reserve energy sources.

17
Structure/function of eubacteria
Ultrastructure
Nuclear area
18
Structure/function of eubacteria
Ultrastructure 6
Nuclear area
  • No nuclear membrane. Nuclear material found near
    the center of the cell and is attached to the
    mesosome-cytoplasmic membrane.
  • Total nuclear material nucleoid consist of a
    single circular chromosome.

19
Structure/function of eubacteria
Ultrastructure
Flagella
20
Structure/function of eubacteria
Ultrastructure 6
Flagella(e)
  • Thin, helical, hair-like filaments extends from
    the cytoplasm through the cell wall. Observable
    in stained specimens.
  • Propels the cell. Up to 100 ?m min-1. 3000 cell
    lengths min-1 cf. the cheetahs top speed of
    1500 body lengths min-1.
  • Polar flagellation monotrichous lophotrichous
    amphitrichous.
  • Peritrichous flagellation

21
Structure/function of eubacteria
Ultrastructure 7
Fimbria(e)
  • Hair-like appendages not related to motility.
    Shorter and straighter than flagella
  • Either polar or even distribution.Number from
    few to thousands.
  • Enables adhesion. A factor in pathogenicity.

22
Structure/function of eubacteria
Ultrastructure 8
Pilus(i)
  • Usually longer than fimbriae.
  • Number only one or two.
  • Join cells in preparation for transfer of
    DNA.Thus also known as sex pili.

23
Structure/function of eubacteria
Ultrastructure 9
Glycocalyx
  • Layer of viscous material (usually
    polysaccharides) outside the cell wall.
    Observation Indian ink stained specimens.
  • When well defined capsule. disorganized slime
    layer.
  • Function Adhesion protection against
    desiccation prevent attachment by bacteriophages
    or attack by white blood cells.

24
Characteristics of viruses
Living organisms?
  • Inert outside a living host
  • Obligatory intracellular parasites
  • Either complex aggregation of non-living
    chemicals or simple living microorganism.
  • Distinctive features
  • Single type of nucleic acid DNA or RNA.
  • Protein coat surrounds the nucleic acid (NA).
  • Synthetic processes of a host living cell used to
    multiply.
  • Specialized structures for transfer viral NA to
    other cells.

25
Characteristics of viruses
26
Viral structure
Virion   A complete, fully developed viral
particle composed of nucleic acid surrounded by a
protective coat which also serves as a vehicle of
transmission from one host cell to another.
Nucleic acid
  • Contrasts with pro- and eucaryotic cells where
    DNA is the primary genetic material.
  • Total NA From a few thousand to as many as
    250,000 nucleotide pairs.E. coli has 4 million
    nucleotide pairs.
  • NA is single or double stranded linear or
    circular.
  • May be in separate segments e.g. influenza virus.

27
Viral structure
Capsid
  • Protein coat surrounding the nucleic acid.
  • Capsomere Protein subunits of the
    capsid. Arrangement is characteristic of each
    particular virus.
  • Nucleocapsid Capsid and nucleic acid as a unit.
  • Capsids give virus types their typical shapes.

28
Viral structure
Envelope
  • Outer membranous layer lipids, carbohydrates and
    proteins.
  • Present in many animal and some plant viruses.
  • In animal viruses Host cell nuclear or plasma
    membranes contribute envelope lipids and
    carbohydrates.Envelope proteins are made by the
    virus.
  • Some have spikes (a.k.a. peplomers) are
    carbohydrate-protein complexes.Thought to be
    involved in attachment to hosts.Useful in
    identification since they differ amongst viruses.

29
Viral structure
Four general morphological types of virion
structure
  • Helical virusesCapsomeres arranged in a helical
    around the nucleic acid.
  • Polyhedral virusesCapsids are icosahedral in
    arrangement (20 equilateral triangular faces and
    12 corners).
  • Enveloped viruses Roughly spherical but
    pleomorphic as the envelope is not rigid. Capsid
    can be helical or polyhedral. Non-enveloped
    viruses are naked viruses.
  • Complex viruses Have capsid symmetry but neither
    purely helical or polyhedral.

30
Viral structure
31
The eucaryotic cell
Protozoa, algae and fungi are eucaryotic.
32
The eucaryotic cell
Ultrastructure
  • Flagella and ciliaFew and long - FlagellaShort
    and few - ciliaMotility movement of substances
    (cilia)Both 9 ring pairs and 2 central
    microtubules.
  • GlycocalyxSurrounds animal cells.Strengthens
    cells also means of attachment to other cell.

33
The eucaryotic cell
Ultrastructure 2
  • Cell wallAlgae and some fungi
    cellulose.Fungi chitin.
  • Cytoplasmic membraneLike procaryotes
    Phospholipid bilayer containing
    proteins.Contains CHO attached to proteins and
    sterols not found in procaryotes.Capable of
    endocytosis.
  • CytoplasmResemble that of procaryotes.Has
    cytoskeleton and exhibits cytoplasmic
    streaming.Unlike procaryotes, many important
    enzymes are sequestered in organelles.

34
The eucaryotic cell
Ultrastructure 3
  • Cell wallAlgae and some fungi
    cellulose.Fungi chitin.
  • Cytoplasmic membraneLike procaryotes
    Phospholipid bilayer containing
    proteins.Contains CHO attached to proteins and
    sterols not found in procaryotes.Capable of
    endocytosis.
  • CytoplasmResemble that of procaryotes.Has
    cytoskeleton and exhibits cytoplasmic
    streaming.Unlike procaryotes, many important
    enzymes are sequestered in organelles.

35
The eucaryotic cell
Ultrastructure 4
Organelles
  • NucleusContains DNA in the form of chromosomes.
    Most characteristic of eucaryotes.

36
The eucaryotic cell
Ultrastructure 5
Organelles
  • Endoplasmic reticulumNot present in
    procaryotes.Provides surface for chemical
    reactions.Serves as transport network.Stores
    synthesized molecules.
  • RibosomesAttached to outer surface of ER but
    also found free.Larger than procaryotic
    ribosomes.Site of protein synthesis.

37
The eucaryotic cell
Ultrastructure 6
Organelles
  • Golgi complexConsists of cisternae.Secretion
    CHO and glycoprotein synthesis.

38
The eucaryotic cell
Ultrastructure 7
Organelles
  • Mitochondrion(a)Folding of inner membrane
    provides large surface area for chemical
    reactions e.g. ATP production (primary site) and
    cellular respiration.Can multiply on their own
    by fission.

39
The eucaryotic cell
Ultrastructure 8
Organelles
  • LysosomesFormed from golgi complexes.Contain
    digestive enzymes to breakdown molecules and
    invasive bacteria.
  • CentriolesRole in cell division and as basal
    bodies in the formation of flagella and cilia.

40
The eucaryotic cell
Ultrastructure 6
Organelles
  • ChloroplastAlgae/green plants only.Contains
    DNA, ribosomes, chlorophyll and photosynthetic
    pigments.Can multiply on their own by fission.
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