Download MICRO Lecture 1

MICROBIOLOGY LECTURE
MICROORGANISMS
These are organisms that are too small to be seen with the unaided eye. A layperson calls
them “germs”, which is a word that is derived from “germinate”, and refers to a rapidly
growing cell. The proper term for a microorganism that causes disease is PATHOGEN. The
prefix “patho” means “disease”, and “gen” means “generating”. Types of pathogens include
fungi (plant molds and yeasts), protozoa (single celled animals), viruses (the smallest; they
can fit inside the nucleus of a bacteria), helminthes (worms), and bacteria. Not all
microorganisms are pathogens; many are useful in the environment and to humans.
BENEFITS OF MICROORGANISMS
1. Decompose organic wastes
2. Are producers in the ecosystem by photosynthesis (algae, cyanobacteria, etc)
3. Produce industrial chemicals such as ethanol and acetone
4. Produce fermented foods such as vinegar, cheese, bread, beer, wine. Fermentation
also produces useful products such as solvents to dissolve substances. To be
“probiotic” means to add microbes to your diet.
5. Produce products used in manufacturing (e.g. cellulose) and treatment of diseases
(e.g E coli can make insulin).
6. Genetic Engineering (recombinant DNA technology)
7. Normal microbiota: normally found on humans, etc, and do not cause disease
except in immunocompromised people(immune system is not strong).
WHY STUDY MICROORGANISMS?
1. Allows humans to prevent food spoilage
2. Prevent disease occurrence and transmission
3. Understanding of aseptic techniques to prevent contamination in medical practice,
surgery, laboratories, patient handling, food and medicine preparation.
a. NOSOCOMIAL DISEASES are those acquired in a hospital.
NAMING AND CLASSIFYING MICROORGANISMS
LINNAEUS (a Swedish Botanist) established the system of scientific nomenclature. Each
organism has two names: GENUS (from the word “genre”, meaning “more than one”)
and SPECIES (specific name unique to that organism type)
The first letter of the genus name is always capitalized, but never the first letter of the
species name. The genus may be abbreviated with the first letter, and the species is
written out. The genus and species of an organism is always either underlined OR
italicized: E. coli or E. coli are both acceptable.
Escherichia coli is the name of a common bacterium normally found in the large
intestine of all humans and animals. If E. coli gets out of that location and into the small
intestine or elsewhere, it can cause disease.
Staphylococcus aureus is the name of a common bacterium that is found on
human skin. If S. aureus gets inside of an open wound, it can cause disease.
HOW NAMES ARE CHOSEN FOR MICROORGANISMS
Named by location of organism: Enterococcus faecalis (located in feces)
Named by the shape of organism: Bacillus megaterium (rod shaped and large)
Named by the arrangement of organism: Staphylococcus aureus (clusters of circles)
CLASSIFICATION OF MICROORGANISMS
SUPERKINGDOMS
1. PROKARYA: Prokaryotes have no nucleus
2. EUKARYA: Eukaryotes have a nucleus
KINGDOMS
1. MONERA
a. BACTERIA
i. Prokaryotes: no nucleus
ii. Peptidoglycan cells walls: a substance that makes them strong
iii. Binary fission: reproduce by splitting in two
iv. Diverse energy requirements: For energy, use organic chemicals
(contains carbon), inorganic chemicals (no carbon), or
photosynthesis (use chlorophyll and sunlight to make food).
v. Normal microbiota are non-pathogenic
vi. Three main types
1. Gram positive
2. Gram negative
3. Spirochetes
b. VIRUSES
i. These are the smallest of all microbes; many viruses and fit into
the nucleus on one bacterium!
ii. They are acellular (no cells)
iii. They consist of a core of either DNA or RNA (not both). The RNA
viruses don’t have stable genes and they mutate frequently.
iv. The core is surrounded by a protein coat called a capsid, made up
of capsomeres. The capsid may be surrounded by an envelope
made up of lipid.
v. Viruses are only replicated when they are living in a host cell.
vi. They don’t have their own metabolism; they use host cells for metabolism.
vii. They are obligate intracellular (must live inside host cell) parasites (live at
the expense of the host, which it weakens or kills).
viii. Even when you kill a virus, it can leave behind an active particle.
ix. Examples of viral diseases range from the deadly HIV to the
common cold virus. Hepatitis A is a virus that can remain viable
(living) even outside of the host for long periods of time; it spreads
through fecal contamination (food workers who do not wash their
hands after a bowel movement).
x. Vaccines can prevent some viral infections, but antibiotics are
ineffective for treatment after infection. Antibiotics work by
interfering with cell wall synthesis or metabolism; since viruses don’t
have these things, they are not effective. There are medicines that treat
but don’t cure viruses, such as acyclovir for Herpes Simplex 1.
c. ARCHAEBACTERIA
i. Prokaryotic
ii. Lack peptidoglycan
iii. Live in extreme environments: deep sea, salt, heat, cold
1. Methanogens: can make methane gas (flatulence!). They
can live in animal bodies (cattle, etc), contributes to global
warming.
2. Extreme Halophiles: like excess salt
3. Extreme thermophiles: like extreme temperatures (hot and cold)
2. PROTISTA(protists)
a. ALGAE
i. These are the producers of the ecosystem because they use
photosynthesis to make food; other organisms eat them and get
their food that way. They are at the bottom of the food chain.
ii. Eukaryotes
iii. Produce oxygen that is needed for all other life forms on earth.
Without algae there would not be enough oxygen on earth.
iv. Don’t cause many diseases
b. PROTOZOA
i. Eukaryotes
ii. Absorb or ingest organic chemicals
iii. May be motile (can move) by pseudopods (false foot), cilia (hairs)
or flagella (tail).
iv. Diseases caused by protozoa include malaria (carried by
mosquitoes) and ameobiasis (food and water poisoning).
3. FUNGI
a. Eukaryotes: have a nucleus in the cell
b. Chitin cell walls or cellulose
c. Heterotrophic: Use organic chemicals for energy
d. Not as diverse as bacteria
e. Two types:
i. Yeasts: unicellular, no mycelia
1. Saccharomyces (Baker’s and Brewer’s yeast)
2. Candida albicans (vaginal yeast infections)
ii. Molds and mushrooms: multicellular, consisting of masses of
mycelia which are composed of filaments called hyphae.
4. PLANTAE (plants)
a. Do not cause many microbiological diseases; not covered in this course.
b. There is some cross-over in taxonomy from one Kingdom to another;
algae can be considered protists and plants.
5. ANIMALIA (animals): We will just cover multicellular animal parasites.
a. Eukaryotes
b. Multicellular animals
c. Endoparasites (animals that live inside other animals through fecal
contamination.
d. Life cycles are seen in stages; they are microscopic.
i. HELMINTHES
1. Flat worms
2. Tapeworms
ii. NEMATODES
1. Roundworms
Taxonomical classification becomes more specific until the organism is uniquely
identified:
Kingdom
Phylum
Class
Order
Family
Genus
Species