Transcript Microbiology: The study of small life

Microbiology:
The study of small life
• All living things divided into 3 domains
– Eubacteria: prokaryotic cell structure
– Archaebacteria: prokaryotes, but different
– Eukaryotes: 4 kingdoms
• Plants, animals, fungi, and protists.
• What are microbiologists interested in?
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Eubacteria and archaebacteria for sure.
Eukaryotes like fungi and protists
Animals (parasitic worms) but not really plants.
What’s missing?
VIRUSES!
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What is “life”?
• Cell theory: all living things are made of cells
– Schleiden and Schwann, 1839
– Eukaryotes and prokaryotes: different kinds of cells
– Excludes viruses, but we can argue later!
• Living things organized into complex structures
– We will compare prokaryotes and eukaryotes
• Living things obtain energy / carry out chemistry
– Bacteria are very diverse in how they do this!
– Most bacteria of medical interest grow by aerobic
metabolism or by fermentation (without oxygen)
– Without energy source, bacteria don’t grow!
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Life?- 2
• Living things are able to reproduce
– All life comes from pre-existing life
– Knowing when and how bacteria reproduce is important
for controlling their growth.
– All living things have DNA as a blueprint
• Living things respond to their environment
– Bacteria are small and simple in structure
– They are successful because they can change themselves
rapidly in response to their environment.
– Bacteria tightly control which genes they use and when.
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The study of chemistry (and biochemistry) is
necessary to understand Microbiology
Habitat
Diet
All living things are made of chemicals!
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Atom: smallest unit of an element
Elements differ by number of protons
http://www.perceptions.couk.com/imgs/atom.gif
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Molecule: atoms joined together with covalent bonds
Electrons are shared between atoms.
Covalent bonds are strong.
When atoms in the molecule are of
different elements, the substance is
called a “compound”.
http://www.truenorthgb.com/images/molecule.jpg
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Covalent bonds & polar molecules
Water
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Covalent Bonds: sharing
of electrons between the
oxygen and hydrogen
atoms. Strong.
Oxygen is an electron
hog; the electrons spend
more time there leaving
the hydrogen’s proton
nearly naked (and
somewhat positive):
Water is a polar molecule
mdp2.phys.ucl.ac.uk/ Talks/Ice/Ice.html
Hydrogen bonds:
• Electrical attraction between electronegative oxygen
atom and nearly naked proton.
• Bonds made between polar molecules.
• Weak bonds.
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H-bonds hold large molecules together
Example: A-T base pair in
DNA
http://www.mun.ca/biology/scarr/Fg10_16a.gif
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Hydrophilic and hydrophobic
Surfaces made of
molecules without
polar groups (e.g.
CH3CH2CH2CH2.)
repel water.
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H2O  H+ + OH-
[H+] = 10-7
pH= -log [H+]
Logarithmic
pH 7 is neutral
Ranges from 0-14
Molecules that
release H+ are acids;
those that release
OH- are bases.
http://www.btinternet.com/~chemistry.diagrams/ph_scale.gif
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Functional Groups
The Chemicals of life are large and small
• Cells contain molecules of all sizes but are MADE
of large molecules called polymers
– Polymer: a large molecule made of many similar or
identical subunits.
– “poly” means “many” (polyethylene, polysaccharide)
– The small molecules that make up a polymer can be
called “monomers”
• “mono” means “one”
• In our, not all polymers are biological
– Plastics are all polymers too
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Small molecules (monomers) and
macromolecules (polymers)
Ethylene and polyethylene
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Four Classes of Biological Molecules
• Carbohydrates
– Sugars and their polymers
• Nucleic acids and nucleotides
– DNA, RNA, ATP
• Lipids
– Various hydrophobic molecules
• Proteins and amino acids
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Carbohydrates: CH2O
Monosaccharides: glucose, fructose, many others
Disaccharides: sucrose, lactose
Oligosaccharides: found on glycoproteins, in cytoplasm
(oligo- means “few”)
Polysaccharides: starch, glycogen, cellulose, agar,
chitin, xanthan gum
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A nucleotide: a monomer of DNA
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/nucleotide.gif
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Nucleic acids are the polymers made from nucleotides.
DNA
tRNA
http://www.biochem.uwo.ca/meds/medna/IMG/tRNA.GIF
Structure of DNA
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http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/16-05-doublehelix.jpg
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Phospholipids are essential
building blocks for membranes;
sterol-type molecules are
rarely found in bacteria.
A lipid polymer: a biodegradable plastic
made by bacteria.
Ester bond
Polyesters
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Peptide bond
covalent bond that connects two amino acids.
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Levels of protein structure
Primary: amino acids and the
order they are in; determined
from the DNA.
Secondary: alpha helix and
beta pleated sheet; twisting
of chain in space.
Tertiary: 3D shape of protein.
Quaternary: more than 1
polypeptide combining to
form a functional unit.
http://www.contexo.info/DNA_Basics/images/proteinstructuresweb.gif
Role of these molecules in cell structure
• Polysaccharides
– Present in protective layers around the cell
– Part of cell wall
• Nucleic acids
– Blueprint of cell, location of genes
– Ribosomes contain RNA
• Lipids
– Major component of cell membranes, barrier
• Proteins
– Enzymes, carry out chemical reactions
– Structural components
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Don’t forget the water
• ALL living things require water
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Water is major component of cytoplasm
All small molecules are dissolved in water
All large molecules have water attached to them
Cells modify their chemistry to retain water
You die of dehydration before you starve
• Every polymer, every structure in the cell is
surrounded by water.
http://media.nasaexplores.com/lessons/04-070/images/faucet.jpg
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Review
• Microbes include
– Bacteria, which are prokaryotic cells
– Fungi and protozoa, which are eukaryotic cells
– Viruses, which are not cellular so maybe not alive
• All of these are comprised of 4 types of molecules
– There’s small and large example of all 4 types
• So Why do we study microbes?
www.pasteur.fr/.../im/micros/pasteur%20copie.jpg
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Why Study Microbes?
• Major impact on health
– Responsible for disease in humans, animals, plants
• Major impact on environment
– Major decomposers
– Nutrient cycling, elemental cycling
• Microbes are talented
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Live under extreme conditions
Protect against disease
Eat oil, toxic waste (bioremediation)
Make plastic
Spoil food, make food
Use light, produce light
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