Download 1. Overview of the Microbial World

Chapter 1:
Introduction
1. Overview of the Microbial World
2. Brief History of Microbiology
3. Ecological Roles of Microbes
1. Overview of the
Microbial World
Evolutionary
Tree of Life
*
*
*
* organisms
covered in
this course
1
Prokaryotes
Archaea:
“tongue” bacteria
• prokaryotic
“extremophiles”
Bacteria:
• colonize all but the most
extreme environments
• chemically and metabolically
very different from archaea
Methanosarcina
Fungi
Characteristics of Fungi:
• all are eukaryotic heterotrophs (eat “organic” food)
• unicellular (yeasts) or multicellular (molds, mushrooms)
• cell walls made of chitin
mold
yeast
Protists
Protists are mostly single-celled eukaryotes:
Protozoa – heterotrophic protists (“animal-like”)
Algae – photosynthetic protists (“plant-like”)
trypanosome
(protozoan)
Volvox
(alga)
2
Helminths
roundworms (Nematodes) &
Helminths = flatworms (Platyhelminthes)
• invertebrate phyla in the Animal Kingdom
• many helminths are disease-causing parasites
Trichinella (nematode)
“tapeworm” (platyhelminth)
Viruses
Non-cellular, “non-living” entities.
tobacco mosaic virus
T4 bacteriophage
• cannot function
without host cell
• frequently
pathogenic
adenovirus
2. Brief History of
Microbiology
3
The Discovery of Microorganisms
Anton van Leeuwenhoek was the first to observe
microorganisms in 1673 using his rather
sophisticated (for the time) “magnifying lenses”.
• essentially began the
field of microbiology
• the importance of
microorganisms for
human welfare was not
appreciated until almost
200 years later!
The Golden Age of Microbiology
Many landmark discoveries in microbiology
occurred in the last half of the 19th century:
• the first vaccine (cowpox lesions to prevent smallpox)
• Edward Jenner (1789)
• importance of aseptic techniques in hospitals
• Ignaz Semmelweis (1848) – hand washing
• Florence Nightingale (1854) – general cleanliness
• Joseph Lister (~1860) – use of surgical antiseptics
• the first epidemiological study (identifying the source of
a cholera outbreak)
• John Snow (1854)
Contributions of Louis Pasteur
• proposed “Germ Theory” of disease (1857)
• disproved concept of spontaneous generation (1861)
• i.e., microbes do NOT arise from non-living material
• showed fermentation
to be carried out by
microbes (1861)
• developed technique
of pasteurization
• developed several
attenuated vaccines
4
Contributions of Robert Koch
• identified the first bacterial pathogens:
• Bacillus anthracis (anthrax – 1876)
• Mycobacterium tuberculosis (tuberculosis – 1882)
• proposed method to identify the microbial agent
responsible for a given disease (Koch’s Postulates)
• developed numerous advances in
microbiological techniques:
• simple staining methods
• fixation of specimens to slides
• use of solid growth media
• pure culture techniques
• methods for counting microbes
Other Landmarks in Microbiology
• first evidence of viruses (tobacco mosaic virus)
• Dmitri Ivanowski (1892)
• the first synthetic antimicrobial chemicals
• Paul Erlich (1908)
• discovery of the first
antibiotic (penicillin)
• Alexander Fleming (1928)
• discovery of prions
• Stanley Prusiner (1997)
3. Ecological Roles
of Microbes
5
Microbes & Ecosystems
Microorganisms play many essential roles in
ecosystems, without which life on our planet
would collapse:
Nitrogen fixation
• conversion of atmospheric nitrogen (N2) into
“bio-available” ammonia and nitrate compounds
• makes nitrogen available for plants and, indirectly,
all other organisms (necessary for proteins, etc)
Photosynthesis
• photosynthetic microbes support aquatic food webs
Decomposition
• essential for the recycling of nutrients
Microbes & Humanity
Microorganisms provide many benefits for
human beings:
Internal and external health benefits
• gut microbes provide digestive help, important
nutrients, protection from pathogenic organisms
• normal skin and mucosal microbes provide protection
from pathogenic organisms
Food production
• wine, cheese, bread, yogurt, etc, depend on microbes
Pollution and pest control
• sewage treatment, cleanup of various pollutants, etc
**very few microbes actually cause human disease**
Key Terms for Chapter 1
• archaea
• heterotroph
• protozoa, algae
• helminth
• spontaneous generation
• nitrogen fixation
Relevant Chapter Questions
rvw: 2, 5
MC: 2, 3, 5-7
6
Chapter 2:
Chemical Principles
1. Atoms & Molecules
2. Biological Macromolecules
1. Atoms & Molecules
Atomic Structure
Atoms are composed of:
Protons (positively charged, 1 amu)
nucleus
Neutrons (no charge, 1 amu)
Electrons (negatively charged, negligible mass)
amu = “atomic mass unit”; atomic mass = protons + neutrons
• # of protons
determines element
• different isotopes of
an element contain
diff. # of neutrons
# of e- = p+ in a neutral atom
• electrons (e-) exist in
orbitals, w/in e- shells
7
Electron Configurations
Molecules & Covalent Bonds
“Happy” atoms have
NO partially filled
electron shells!
Molecular weight (MW)
= sum of atomic
masses in a molecule
Atoms share electrons to fill electron shells
• sharing of unpaired e- = covalent bond
• basis of molecules (multiple atoms joined by cov. bonds)
Water & Hydrogen Bonding
Water is a polar molecule due to polar O-H bond:
• polar covalent bond = electron pair shared unequally
• nonpolar covalent bond = electron pair shared equally
• hydrogen bonds are weak
interactions between opposite
partial charges due to polar bonds
8
Ions & Ionic Bonds
Ions have gained or lost an electron(s),
…and can form ionic bonds
due to the attraction of oppositely charged ions.
Water as a Solvent
Water’s polar nature makes it
a great solvent for other polar
or charged substances.
• polar water
molecules
neutralize
and shield
the solute
*doesn’t work
for nonpolar
solutes
(e.g., oils)*
Ionic Compounds Dissociate in Water
Acids (release H+ ions), bases (release OH- ions which
then combine with H+), and salts (ionic compounds w/o
OH- or H+) all dissolve and dissociate (split) into ions
very easily in water.
9
Acids, Bases & pH
Acids release H+
ions into solution
• raise [H+]
• lower pH
Bases remove H+
ions from solution
• lower [H+]
• raise pH
pH = –log of [H+]
[H+] x [OH-] = 10-14 M
buffers are molecules
that resist pH change
2. Biological Molecules
Functional Groups
common molecular groups found in organic molecules
10
Carbohydrates
Simple sugars
• mono- and disaccharides (e.g., glucose, sucrose)
Complex carbohydrates
• polysaccharides (e.g., starch, glycogen, cellulose)
Biological roles:
• energy source
• structure, physical support & protection
• adhesion, molecular “recognition”
Lipids
Hydrophobic (nonpolar)
biological molecules:
• fatty acids
• triglycerides
• phospholipids
• steroids
Biological roles:
• membranes, energy source &
storage, communication
Phospholipids & Membranes
Phospholipids have “polar heads”, “nonpolar tails”
• form a lipid
bilayer in
water
• the major
component
of biological
membranes
(which have
cholesterol
and proteins
as well)
11
Proteins
Polymers of amino acids connected by
peptide bonds (i.e., polypeptides).
• made from 20
amino acids
(differ in their
“R” groups)
• proteins have
extremely
diverse
biological roles
Protein
Structure
1o
2o
Protein function
is entirely
dependent on
protein structure.
Protein structure
is entirely
dependent on
the amino acid
sequence.
3o
4o
Nucleic Acids
DNA, RNA
• polymers of
nucleotides
• store genetic info
• gene expression
ATP
• direct source of
energy in cells
12
Key Terms for Chapter 2
• isotope, atomic mass, molecular weight
• valence
• covalent bond, ionic bond, hydrogen bond
• polar vs nonpolar bond
• solvent, solute
• acid, base, salt, pH, buffer
• carbohydrate, lipid, protein, nucleic acid
Relevant Chapter Questions
rvw: 1-7, 10-14
MC: 1-10
13