Title: Characteristics of microbes
1Characteristics 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.
2Characteristics 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.
3Structure/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
4Structure/function of eubacteria
Size, shape and arrangement 2
5Structure/function of eubacteria
Size, shape and arrangement 3
6Structure/function of eubacteria
Ultrastructure
Cell wall
7Structure/function of eubacteria
Ultrastructure 2
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.
8Structure/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.
9Structure/function of eubacteria
Ultrastructure 3
10Structure/function of eubacteria
Ultrastructure 4
There are 2 types of cells wall in eubacteria
- Differences in the layering and presence of outer
membrane (in G -)explains the difference in Gram
reaction and pathogencity.
11Structure/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).
12Structure/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).
13Structure/function of eubacteria
Ultrastructure 5
Cytoplasmic membrane
- Composition Phospholipids 20 - 30
Proteins 50 - 70
14Structure/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.
15Structure/function of eubacteria
Ultrastructure
Cytoplasmic area
16Structure/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.
17Structure/function of eubacteria
Ultrastructure
Nuclear area
18Structure/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.
19Structure/function of eubacteria
Ultrastructure
Flagella
20Structure/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
21Structure/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.
22Structure/function of eubacteria
Ultrastructure 8
Pilus(i)
- Usually longer than fimbriae.
- Join cells in preparation for transfer of
DNA.Thus also known as sex pili.
23Structure/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.
24Characteristics 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.
25Characteristics of viruses
26Viral 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.
27Viral 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.
28Viral 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.
29Viral 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.
30Viral structure
31The eucaryotic cell
Protozoa, algae and fungi are eucaryotic.
32The 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.
33The 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.
34The 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.
35The eucaryotic cell
Ultrastructure 4
Organelles
- NucleusContains DNA in the form of chromosomes.
Most characteristic of eucaryotes.
36The 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.
37The eucaryotic cell
Ultrastructure 6
Organelles
- Golgi complexConsists of cisternae.Secretion
CHO and glycoprotein synthesis.
38The 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.
39The 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.
40The eucaryotic cell
Ultrastructure 6
Organelles
- ChloroplastAlgae/green plants only.Contains
DNA, ribosomes, chlorophyll and photosynthetic
pigments.Can multiply on their own by fission.