1

Chapter 1:Introduction

2. Brief History of Microbiology

3. Ecological Roles of Microbes

1. Overview of the Microbial World

1. Overview of the Microbial World

Evolutionary Tree of Life

* *

* organismscovered in this course

*

2

Prokaryotes

Bacteria:

Archaea:

• colonize all but the mostextreme environments

• prokaryotic“extremophiles”

• chemically and metabolicallyvery different from archaea

“tongue” bacteria

Methanosarcina

FungiCharacteristics of Fungi:• all are eukaryotic heterotrophs (eat “organic” food)

• unicellular (yeasts) or multicellular (molds, mushrooms)

• cell walls made of chitin

mold yeast

Protists

Protozoa –Algae –

heterotrophic protists (“animal-like”) photosynthetic protists (“plant-like”)

Protists are mostly single-celled eukaryotes:

trypanosome(protozoan)

Volvox(alga)

3

HelminthsHelminths =

• invertebrate phyla in the Animal Kingdom

roundworms (Nematodes) &flatworms (Platyhelminthes)

• many helminths are disease-causing parasites

Trichinella (nematode) “tapeworm” (platyhelminth)

VirusesNon-cellular, “non-living” entities.

• cannot functionwithout host cell

• frequentlypathogenic

tobacco mosaic virus

T4 bacteriophage

adenovirus

2. Brief History of Microbiology

4

Anton van Leeuwenhoek was the first to observe microorganisms in 1673 using his rather sophisticated (for the time) “magnifying lenses”.

• essentially began thefield of microbiology

• the importance of microorganisms for human welfare was notappreciated until almost200 years later!

The Discovery of Microorganisms

The Golden Age of MicrobiologyMany landmark discoveries in microbiology occurred in the last half of the 19th century:

• importance of aseptic techniques in hospitals • Ignaz Semmelweis (1848) – hand washing

• the first epidemiological study (identifying the source ofa cholera outbreak)

• John Snow (1854)

• the first vaccine (cowpox lesions to prevent smallpox)• Edward Jenner (1789)

• Florence Nightingale (1854) – general cleanliness• Joseph Lister (~1860) – use of surgical antiseptics

Contributions of Louis Pasteur

• disproved concept of spontaneous generation (1861) • i.e., microbes do NOT arise from non-living material

• proposed “Germ Theory” of disease (1857)

• showed fermentation to be carried out bymicrobes (1861)

• developed techniqueof pasteurization

• developed severalattenuated vaccines

5

Contributions of Robert Koch• identified the first bacterial pathogens:

• proposed method to identify the microbial agentresponsible for a given disease (Koch’s Postulates)

• developed numerous advances in microbiological techniques:

• simple staining methods

• fixation of specimens to slides

• pure culture techniques

• methods for counting microbes

• Bacillus anthracis (anthrax – 1876)• Mycobacterium tuberculosis (tuberculosis – 1882)

• use of solid growth media

Other Landmarks in Microbiology

• the first synthetic antimicrobial chemicals• Paul Erlich (1908)

• first evidence of viruses (tobacco mosaic virus)• Dmitri Ivanowski (1892)

• discovery of the firstantibiotic (penicillin)

• Alexander Fleming (1928)

• discovery of prions• Stanley Prusiner (1997)

3. Ecological Rolesof Microbes

6

Microbes & EcosystemsMicroorganisms 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 & HumanityMicroorganisms provide many benefits for human beings:Internal and external health benefits

• gut microbes provide digestive help, importantnutrients, protection from pathogenic organisms

• normal skin and mucosal microbes provide protectionfrom 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

• heterotroph

Relevant Chapter Questions rvw: 2, 5 MC: 2, 3, 5-7

• helminth

• protozoa, algae

• spontaneous generation

• archaea

• nitrogen fixation

7

Chapter 2:Chemical Principles

2. Biological Macromolecules

1. Atoms & Molecules

1. Atoms & Molecules

Atomic StructureAtoms are composed of:

Protons (positively charged, 1 amu)

Neutrons (no charge, 1 amu)

Electrons (negatively charged, negligible mass)

nucleus

amu = “atomic mass unit”; atomic mass = protons + neutrons

• # of protons determines element

• different isotopes ofan element containdiff. # of neutrons

• electrons (e-) exist inorbitals, w/in e- shells# of e- = p+ in a neutral atom

8

Electron Configurations

Molecules & Covalent Bonds

Atoms share electrons to fill electron shells• sharing of unpaired e- = covalent bond

“Happy” atoms have NO partially filled electron shells!

• basis of molecules (multiple atoms joined by cov. bonds)

Molecular weight (MW)= sum of atomic

masses in a molecule

Water & Hydrogen BondingWater 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 weakinteractions between oppositepartial charges due to polar bonds

9

Ions & Ionic BondsIons have gained or lost an electron(s),

…and can form ionic bondsdue to the attraction of oppositely charged ions.

Water as a SolventWater’s polar nature makes it a great solvent for other polar or charged substances.

• polar watermoleculesneutralizeand shieldthe solute

*doesn’t workfor 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.

10

Acids, Bases & pHAcids 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 moleculesthat resist pH change

2. Biological Molecules

Functional Groups

common molecular groups found in organic molecules

11

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”

LipidsHydrophobic (nonpolar) biological molecules:

• fatty acids• triglycerides• phospholipids• steroids

Biological roles:• membranes, energy source &storage, communication

Phospholipids & MembranesPhospholipids have “polar heads”, “nonpolar tails”

• form a lipidbilayer in water

• the major componentof biologicalmembranes(which havecholesteroland proteinsas well)

12

ProteinsPolymers of amino acids connected by peptide bonds (i.e., polypeptides).

• made from 20amino acids(differ in their“R” groups)

• proteins haveextremely diversebiological roles

ProteinStructureProtein function is entirely dependent onprotein structure.

Protein structure is entirely dependent onthe amino acid sequence.

1o

2o

3o

4o

Nucleic AcidsDNA, RNA

• polymers of nucleotides

• store genetic info• gene expression

ATP• direct source of

energy in cells

13

Key Terms for Chapter 2

• valence

• polar vs nonpolar bond

• covalent bond, ionic bond, hydrogen bond

• solvent, solute

• isotope, atomic mass, molecular weight

Relevant Chapter Questions rvw: 1-7, 10-14 MC: 1-10

• acid, base, salt, pH, buffer

• carbohydrate, lipid, protein, nucleic acid