Microbes: the most successful creatures on earth?

1
Microbes the most successful creatures on earth?

• Is evolution driving towards perfection or
  greater complexity?
• Prokaryotes are the simplest form of what
  scientists usual consider life.
• Prokaryotes have been around for 3.8 billion
  years and they are still here!
• So whats the most successful form of life?

2
Why you think bacteria are simple

• Prokaryotic cells are only a fraction of the size
  of eukaryotes
• Most bacteria are 1 5 µm in size eukaryotes
  are 25x that size.
• Bacteria have no internal organelles
• No nucleus (but yes, DNA), no mitochondria, no
  endoplasmic reticulum (but they do have
  ribosomes)
• We are smarter
• We can kill them with disinfectants and
  antibiotics

3
Why bacteria are more clever than you

• Nutrition
• Give E. coli a simple nutrient source with
  mineral salts to supply N, P, S, and other
  elements, and only glucose as source of C, H, and
  O and it will grow.
• You would die. You need
• 8 different amino acids
• Vitamins (A, many B vitamins, C, D, etc.)
• Habitat
• Different bacteria can live in places with
  extremes in pH, temperature, with and without
  oxygen

4
How are bacteria classified?

• Taxonomy of cellular creatures
• Three domains
• Eubacteria prokaryotic cell structure
• Archaebacteria prokaryotes, but different
• Eukaryotes 4 kingdoms
• Prokaryotes look alike
• Archaea and eubacteria very similar
• Differences are genetic, biochemical, and
  ecological

5

• Why Study Microbes?
• Major impact on health
• Responsible for disease in humans, animals,
  plants
• Major impact on environment
• Major decomposers
• Nutrient cycling, elemental cycling

6
Microbes are talented

• Live under extreme conditions
• Protect against disease
• Eat oil, toxic waste (bioremediation)
• Make plastic
• Spoil food, make food
• Use light, produce light

7
Bacterial Appearance

• Size
• 0.2 µm 0.1 mm
• Most 0.5 2.0 µm

• Shape
• Coccus (cocci) rod (bacillus, bacilli) spiral
  shapes filamentous various odd shapes.
• Arrangement
• Clusters, tetrads, pairs, chains

http//smccd.net/accounts/case/biol230/ex3/bact.jp
eg
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How are bacteria put together?

• A cell membrane
• Separates inside from outside
• Cytoplasm
• No organelles
• Nucleoid instead of nucleus
• Ribosomes
• Cell wall (usually)
• In Eubacteria, made partly of peptidoglycan
• Outer layers

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Overview of prokaryotic cell.
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Division of the EubacteriaGram Negative and
Gram Positive

• Gram stain invented by Hans Christian Gram
• Gram positive cells stain purple Gram negatives,
  pink.
• Architecture
• Gram positives have a thick peptidoglycan layer
  in the cell wall
• Gram negatives have a thin peptidoglycan layer
  and an outer membrane.
• Stain is valuable in identification.

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Gram Negative Gram Positive
http//www.conceptdraw.com/sampletour/medical/Gram
NegativeEnvelope.gif http//www.conceptdraw.com/sa
mpletour/medical/GramPositiveEnvelope.gif
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Function and Structure of peptidoglycan

• Provides shape and structural support to cell
• Resists damage due to osmotic pressure
• Provides some degree of resistance to diffusion
  of molecules
• Single bag-like, seamless molecule
• Composed of polysaccharide chains cross linked
  with short chains of amino acids peptido and
  glycan.
• Many antibiotics work by preventing bacteria from
  producing this cell wall material.

13
Bacteria and Osmotic pressure

• Bacteria typically face hypotonic environments
• Insides of bacteria filled with proteins, salts,
  etc.
• Water wants to rush in, explode cell.
• Peptidoglycan provides support
• Limits expansion of cell membrane
• Growth of bacteria and mechanism of penicillin
• Bacteria need different protection from
  hypertonic situations
• Water leaves the cell cell membrane shrinks
• Lack of water causes precipitation of molecules,
  death

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Effect of osmotic pressure on cells

• Hypotonic water rushes in PG prevents cell
  rupture.
• Hypertonic
• water leaves cell, membrane pulls away from cell
  wall.

15
Glycocalyx capsules and slime layers
Sugar covering capsules are firmly attached,
slime layers are loose.
Multiple advantages to cells prevent
dehydration absorb nutrients protection from
predators, WBCs protection from biocides (as
part of biofilms) attachment to surfaces and
site of attachment by others.
cell
capsule
www.activatedsludge.info/ resources/visbulk.asp
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Fimbriae and pili
Both are appendages made of protein Singular
fimbria, pilus Both used for attachment Fimbriae
to surfaces (incl. host cells) and other
bacteria. Pili to other bacteria for exchanging
DNA (sex).
www.ncl.ac.uk/dental/oralbiol/ oralenv/images/sex1
.jpg
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Fimbriae and pili-2
http//www.mansfield.ohio-state.edu/sabedon/006pi
li.gif
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Flagella

• Flagella protein appendages for swimming through
  liquid or across wet surfaces.
• Rotate like propellers.
• Different from eukaryotic flagella.

www.ai.mit.edu/people/ tk/ce/flagella-s.gif
www.bmb.leeds.ac.uk/.../icu8/ introduction/bacteri
a.html
19
Energy and nutrition

• Bacteria as a whole have several different ways
  of obtaining carbon and energy
• Thus they are adapted to many types of
  environments.
• Heterotrophs use pre-existing organic molecules
• Get energy aerobically or anaerobically (or both)
• Some are autotrophs get carbon from CO2
• Some get energy from light photosynthetic
• Some oxidize inorganic minerals
• Play various roles in the cycling of different
  elements on the planet play different roles in
  food webs

20
Archaea vs. EubacteriaSo whats the difference?

• Genetic
• Ribosomal RNA genes different
• Biochemistry
• Cell wall polymer not peptidoglycan, but similar
• Lipids in membranes unusual
• Ecology
• Tend to live in extreme environments
• Very anaerobic, very salty, very acidic and/or
  very hot

21
Eubacteria little disease-causing monsters?

• Hardly. Most bacteria have never been grown in a
  lab, never mind on your tissues.
• Live in soil, water, in association with other
  organisms.
• Some do make you sick

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Bacterial diseases

• Staph infection, E. coli infection, Strep throat
• Anthrax, tularemia, plague
• Syphilis, gonorrhea, chlamydia infection
• tuberculosis