Transcript Bacteria and Viruses Chapter 19 Taxonomy • The branch of biology dealing with the classification of life. • 1700s 2 kingdoms: plant and animal •

Bacteria and Viruses
Chapter 19
Taxonomy
• The branch of biology dealing with the
classification of life.
• 1700s 2 kingdoms: plant and animal
• 1800s 3 kingdoms: plant, animal, and
protista
• 1950-1990s 5 kingdoms: plant, animal,
protista, fungi, monera
• Present: 6 kingdoms: eubacteria,
archaebacteria, protista, animal, plant,
fungi
Prokaryotes
• Traditionally all prokaryotes were
classified as Monerans Gr. 1. Single or
one
• Also known as bacteria (p.) or
bacterium (s.)
• Presently, the prokaryotes are divided
into two kingdoms.
1. K. Eubacteria
• Larger of the two kingdoms
• Live almost everywhere
• Vital for life functions and
industry
• Both helpful and harmful
2. K. Archaebacteria
• Comes from the Greek word archaio
which means “ancient”
• Believed by many to be the earliest
organisms to inhabit the earth
• All live in harsh environments
• 3 separate phyla:
1. Methane-producing
bacteria (methanogens)
• Intestinal tracts
of animals
• Bottoms of
swamps
• Used for sewage
treatment
2. Salt-loving bacteria
(Halophiles)
• Thrive in high
salinity waters
where no other
life can exist.
• Great Salt
Lake
• Dead Sea
3. Hot-acidic loving
(thermoacidophiles)
• Thrive at
temperatures as
great as 180ºF
and pHs as low as
2.
• Natural springs.
• Yellowstone
National Park
Facts about bacteria:
• Found everywhere
• Very small. Much smaller than any cell
in our body.
• No membrane-bound structures or
nucleus. (prokaryotes)
• Usually surrounded by a cell wall and a
capsule for additional protection.
General structure:
Classification according
to shape.
1.




Coccus (spherical)
Can be single cells
Pairs
Chains
example
 Strep throat
Bacillus (rod)
• Single cells
• Pairs
• Chains
2.
• example
– anthrax
3.
Spirillum(spiral)
Only exist as single cells
Example:
cholera, syphillis
Shapes:
Gram-positive bacteria
• Chemical nature of cell wall allows
these bacteria to retain the violet
stain.
• Can be harmed by antibiotics like
penicillin
• example: streptococcus
Gram-negative bacteria
• More difficult to penetrate cell wall.
• Usually more difficult to treat with
antibiotics
• Example: E-coli
Movement
• Usually move through flagella
or gliding along a surface.
• Surface Structures
Metabolic Needs
• Anaerobic
• Aerobic
• Cannot live in the
• The most
presence of
common type
oxygen
• Gets energy
• Cannot live
through
without oxygen
fermentation
(CO2)
Heterotrophic bacteria
• Saprobes
• Parasites
• Feed off the
• Live on or in
remains of
other living
dead plants and organisms.
animals.
Often cause
Seldom cause
disease
disease
Autotrophic bacteria
• Photoautotroph • Chemoautotroph
• Use sunlight to
convert carbon
dioxide into energy
• Ex. cyanobacteria
• Use inorganic
chemical
compounds to
convert carbon
dioxide into
energy.
Genetic material
• Nucleoid= a single
circular
chromosome
containing the DNA
and RNA.
• Endospore = tough
protective coat
that covers and
protects the
nuclear material.
Reproduction
• All reproduce asexually
• Usually through binary fission
• Under certain conditions, bacteria can
reproduce very quickly
– A small colony can double in 20
minutes.
– animation
Binary fission
• The most
common type of
asexual
reproduction.
• A single cell
splits to form
two daughter
cells
Exchange of DNA
Conjugation =
genes move
from one
cell to
another
Endospores
• A thick covering
around the DNA
that allows the
bacterium to
remain dormant for
long periods of
time. If necessary,
many years.
Helpful bacteria
•
•
•
•
•
Decompose food wastes
Produce vitamins
Produce antibodies
Genetic engineering
Decomposition of dead plants and
animals
• Industry & agriculture
Plant roots
• Found on the
roots of plants.
• Can be helpful in
‘fixing’ nitrogen
for plant use.
• Rhizobium
nodules on roots
of soybeans
• Are they living or non-living?
• Contain genetic material
• Lack organelles
Cannot reproduce unless inside a host
cell.
• The word virus comes from the Greek
word for POISON
• Cause many diseases.
How big is a virus?
• Much smaller than
bacterial cells.
• Scientists have only
recently, last 60
years, learned
anything about
viruses
• Classified
according to the
types of cells they
attack.
Virus structure:
• A center core of DNA or RNA
surrounded by a protein coat
called a capsid.
2 main types of viral
reproduction:
• LYTIC CYCLE
1. Injects its
nucleic acid
(DNA or RNA)
into the cell to
take over
cellular
activities.
• LYSOGENIC
CYCLE
1. Coexists with
the cell
without
destroying
the host cell
Lytic cycle
Lysogenic cycle
• Direct the production of proteins by
the host cell.
• RETROVIRUS = A special type of
virus that can make DNA which will
produce new RNA, which, in turn,
makes proteins that produce new
viruses.
• Ex.
Diseases caused by
microorganisms:
• Pathogens: disease-causing
agents
• BACTERIAL DISEASE:
1) Damage cells and tissues
directly
2) Release toxins to interfere with
normal cellular activity
Common bacterial
diseases:
• Lyme disease
• Tetanus
• Strep throat
• Tuberculosis
• E. coli poisoning
Controlling bacterial
disease.
• ANTIBIOTICS
• 1928. Discovery
of penicillin by
Sir Alexander
Flemming
• Came from a
mold.
Common methods of
bacterial infection.
• Food & water
(E. coli)
• Coughing &
sneezing
• Sexually
transmitted.
• Carried by
insects
Food disease prevention
• Keep hands, and cooking
utensils clean
• Canning and preservation
techniques with food.
• Pasteurization
• Freezing
How do we prevent viral
diseases?
• Cannot be treated with ordinary antibiotics
• Vaccinations. The word comes from the
vacca Latin for “cow”.
• A vaccine is a weakened form of a virus
that is used to stimulate the immune
system to produce antiviral substances.
Edward Jenner (17491823)
• British physician
• Developed the
first vaccine in
1798 for the
viral disease
smallpox.
• Considered the
“Father of
Immunology”
Common viral diseases:
•
•
•
•
•
•
•
•
AIDS
Measles
Chickenpox
Smallpox
Influenza
The common cold
West Nile
Polio
• Viral disease that is believed to have
originated in Egypt at least 2000
years ago.
• Characterized by pox lesions and
boils.
• Spread to the Americas by Spanish
conquistadors.
• Jenner’s vaccine was developed after
observing a bovine disease: “cowpox”
Eradication of smallpox:
• In 1967 the World Health
Organization launched a global effort
to eradicate smallpox.
• 1978 : Last known case of smallpox.
• 1980 : W.H.O. declares the world free
of smallpox.
• Is there any smallpox virus left?
Viroids and Prions
• Viroid
• Small disease
causing
particle.
• Affect plants
• Prion
• Small disease
causing particle.
• Affects animals.
• example:
Assignment:
• Pages 493
• 1-10,11,12,13,19,22,23,24
• Page 495
• 1-12