Transcript Monerans, Protists, & Viruses

Bacteria and Viruses
Chapter 19
anthrax
Strep throat
19-1 BACTERIA
• BACTERIA ARE CLASSIFIED AS
PROKARYOTES – UNICELLULAR
ORGANISMS THAT LACK A NUCLEUS
• CLASSIFYING PROKARYOTES
– EUBACTERIA – LARGER OF THE TWO
KINGDOMS
• LIVE IN FRESH WATER, SALT WATER, LAND,
AND ON AND IN HUMAN BODY.
Prokaryotes
• Traditionally all prokaryotes were
classified as Monerans
• Also known as bacteria (p.) or
bacterium (s.)
• Presently, prokaryotes are divided
into two kingdoms Archaebacteria &
Eubacteria
1. K. Eubacteria
• Larger of the two kingdoms
• Live almost everywhere
• Vital for life functions and
industry
• Both helpful and harmful (E.
coli!)
2. K. Archaebacteria
• Believed to be earliest organisms to
inhabit the Earth
• All live in harsh environments
• DIFFER FROM EUBACTERIA BY:
– NO PEPTIDOGLYCAN
– DIFFERENT MEMBRANE LIPIDS
– DNA more like eukaryotes’ DNA
• 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:
IDENTIFYING
PROKARYOTES
• IDENTIFIED BY SHAPE, CELL
WALLS, MOVEMENT FLAGELLA, WAY THEY GET
ENERGY
– SHAPES:
– BACILLI (RODS),
COCCI (SPHERES),
SPIRILLA (SPIRAL)
Classification according
to shape.
1. Coccus (spherical)
 Can be single cells, pairs, or
chains
 Example: Strep throat
Bacillus (rod)
• Single cells
• Pairs
• Chains
2.
• Example: anthrax
3.
Spirillum(spiral)
Only exist as single cells
Example:
cholera, syphilis
Shapes:
4 Ways to Classify
Bacteria
1. shape
2. Chemical nature of cell walls
(Gram + or gram -)
3. How they move
4. How they obtain energy
Gram-positive bacteria
• Two kinds of cell walls in Eubactiera
• Gram-positive bacteria have cell walls
that are dyed a violet stain.
• Can be harmed by antibiotics like
penicillin
• example: streptococcus
Gram-negative bacteria
• More difficult to penetrate cell wall.
• Appear pink/red in Gram stain
• Usually more difficult to treat with
antibiotics
• Example: E-coli
Movement
• Usually move through flagella
or gliding along a surface.
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
2 types of heterotrophic
bacteria
• Chemoheterotrophs – take in organic
molecules for energy and carbon
(like humans!)
– Largest group of bacteria!
• Photoheterotrophs – use sunlight for
energy, but also need to take in
organic compounds
Autotrophic bacteria
• Photoautotroph • Chemoautotroph
• Use sunlight to
convert carbon
dioxide into energy
• In lakes/streams/
oceans
• Ex. cyanobacteria
• Use inorganic
chemical
compounds to
convert carbon
dioxide into
energy.
Releasing Energy
1. Obligate aerobes: require
oxygen
2. Obligate anaerobes: cannot
live in presence of oxygen
3. Facultative anaerobes: do
not need oxygen, but can live
in the presence of it (E. coli)
E. Growth and Reproduction
1. Binary fission: cell divides,
asexual
2. Conjugation: transfer of genetic
information from one cell to another,
sexual
3. In unfavorable conditions, many
bacteria can form endospores – can
remain dormant for months or years
(such as anthrax)
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.
Importance of Bacteria
• Without bacteria, we would die!
• Bacteria produce energy,
decompose dead matter into
nutrients, convert nitrogen for
plants, and produce vitamins in
our intestines
Helpful bacteria
• Decompose food wastes
• Produce antibodies
• Genetic engineering – bacteria can produce
heat-stable enzymes for medicines
• Decomposition of dead plants and animals
• Industry & agriculture – cleaning oil spills
• Break down sewage into water, carbon
dioxide, nitrogen
Bacteria on Plant roots
• Can be helpful in
‘fixing’ nitrogen
for plant use.
• Rhizobium
nodules on roots
of soybeans
convert nitrogen
into ammonia
Controlling Bacteria
1. Sterilization: destroy bacteria by
subjecting them to great heat or
chemicals
a. Boiling, frying, steaming can
all
kill bacteria
b. Disinfectant chemical
solutions can be used in
homes and hospitals
2. Refrigeration – bacteria grow
slowly at low temperatures
• 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.
Section 19.2 Viruses
A. Viruses: particles of
nucleic acid and protein
1. Nucleic acid = DNA
or RNA that contains
instructions for making
new copies of the virus
2. Capsid: outer protein
coat
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.
Viral Body
Plans
• Genetic material
is DNA or RNA
• Coat is protein
Helical virus
Polyhedral virus
Complex virus
(bacteriophage)
DNA and RNA Review
DNA – deoxyribonucleic acid
chemical compound (containing
hydrogen, oxygen, nitrogen, carbon, and
phosphorus) with instructions for coding
proteins that determines your genetic
makeup
RNA – ribonucleic acid - nucleic acid
that contains the sugar ribose
Viral Infections
A virus binds to proteins on a cell
and enters the cell
•
1. Infect cells and replicate
inside host cell
•
2. Bacteriophage: viruses
that infect bacteria
2 types of viral
infections
a. Lytic infection: virus
enters cell, makes copies of
itself and causes the cell to
burst
b. Lysogenic infection: virus
embeds its DNA into DNA of
host and is replicated with host
cell’s DNA
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
The Prophage
• Prophage = viral DNA that is
inserted into a cell
• The prophage can have the cell
make copies of the virus right
away or may wait several
generations (a latent infection)
and then begins making copies at
a later time
Viruses and Disease
1. Many viruses can be prevented
through the use of vaccines
(polio, measles, influenza)
2. Oncogenic viruses cause cancer
3. Retroviruses contain RNA
4. Prions contain no DNA or RNA, only
protein
• 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.
Bacteria and Disease
1. Pathogen: disease-causing
agents
2. 2 ways bacteria cause disease
a. Break down tissues for food
b. Release toxins to interfere
with normal cellular activity
3. Many can be prevented with
vaccines, can be treated with
antibiotics
Common bacterial
diseases:
• Lyme disease
• Tetanus
• Strep throat
• Tuberculosis
• E. coli poisoning
Controlling bacterial
disease.
• ANTIBIOTICS –
compounds that
block the growth
and reproduction of
bacteria
• 1928. Discovery of
penicillin by Sir
Alexander Fleming
Common methods of
bacterial infection.
• Food & water
(E. coli)
• Coughing &
sneezing
• Sexually
transmitted.
• Carried by
insects
Controlling Bacterial
Growth
• Sterilization by heat – most
bacteria are killed by high heat!
• Disinfectants – chemical
solutions that kill pathogenic
bacteria
• Food storage –
boiling/frying/steaming kills,
bacteria take longer to multiply
in fridge (cooler temperatures)
How do we prevent viral
diseases?
• Cannot be treated with ordinary antibiotics
• Prevention is best way to protect against
viral diseases:
• 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:
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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?
Smallpox
upmc-biosecurity.org
Viroids and Prions
• Viroid
• Small disease
causing
particle.
• Affect plants
• Prion
• Small disease
causing particle.
• Affects animals.
• example: