Download Microbes Notes

Microbes – Bacteria, Viruses,
Protists and Fungi
Prokaryotes
• Prokaryote – unicellular organism
without a nucleus
– DNA is found in the cytoplasm
Classifying Prokaryotes
• 2 Kingdoms of Prokaryotes
– Eubacteria
• Have peptidoglycan in cell walls
• Includes most of the bacteria
– Archaebacteria
• Live in unusually harsh
environments such as hot springs,
stomach acid, and salty water.
• No peptidoglycan in cell walls
• Cell membranes and rRNA different
than Eubacteria
Identifying Prokaryotes
•
Prokaryotes can be identified
based on the following:
1. Shapes
2. Cell Walls
3. Movement
Shapes
• 3 Shapes
1.Bacilli – rod shaped
2.Cocci – spherical shaped
3.Spirochetes – spiral & corkscrew
shaped
Cell Walls
• Eubacteria can be separated based
on Gram staining.
– Gram Positive
• Eubacteria cell walls have a thick layer of
peptidoglycan that absorbs only violet dye
and appears purple.
– Gram Negative
• Have an extra layer of lipid on the cell
wall that stops the purple stain from
entering and appears pink
Movement
• Stationary
– Some bacteria do not move.
• Flagella (tails)
– Whip like structures used for movement.
• Other
– Spiral shaped bacteria move in a corkscrew
Motion
– Myxobacteria produce a layer of slime to
glide in.
Obtaining Energy
• Autotrophs (Make their own energy)
– Photoautotroph – uses the sun
– Chemoautotroph – oxidize inorganic
compounds as food.
• Heterotrophs (Rely on other organisms
for energy)
– Fermentation – ferment sugars
– Saprophytes – feed on dead things
• Photoheterotrophs (A mix between the
two)
– are both autotrophic and heterotrophic
– Use energy from the sun, but they require
organic substances such as alcohol, fatty
acids or carbohydrates.
Growth and Reproduction
• Bacteria divide very quickly, as often as once
every 20 minutes!
• Binary Fission
– Asexual reproduction where the bacteria
divide into identical cells.
Endospore
• Endospore – a structure produced
in unfavorable conditions
- A thick internal wall encloses the DNA
and cytoplasm
Gene Transfer
(Bacterial Evolution)
• Mutation – random changes in DNA
-passed on to daughter cells
-one of the main way prokaryotes evolve
• Conjugation
– Bacteria make a bridge and exchange
genetic material.
• Transformation
– Bacteria incorporate DNA from dead
bacteria.
• Transduction
– Use viruses to transfer DNA from bacteria to
other bacteria.
Importance of Bacteria
• Decomposers
• Producers
• Nitrogen Fixers
Decomposers
• Decomposers
– Bacteria that break down complex
molecules of dead organisms (trees,
corpses) into simple molecules such
as water, nitrogen compounds, and
CO2
Producers
• Producers – food chains are
dependent on bacteria for
producing food
– 1 cyanobacterium (Prochlorococcus) is
the most abundant photosynthetic
organism – makes over ½ of food in the
open ocean
Nitrogen Fixers
• Nitrogen Fixers – converts nitrogen
into a form plants use (N2 to NH3)
– 90% of the nitrogen organisms use comes
from fixation
– Fix nitrogen to ammonia.
– Ex: Rhizobium grows in nodules of the roots
of soybeans and other legumes. It is a
mutual relationship where the plant provides
nutrients for bacteria and the bacteria
converts nitrogen for the plant.
Bacteria and Disease
•
Pathogens
–
•
Disease causing agents.
2 Ways Bacteria cause Disease
1. Damage Tissues – damage tissues of the
infected organisms directly by breaking
them down for food.
–
Ex: Tuberculosis – bacteria break down lung
tissue.
2. Toxins – release toxins that harm the
organism.
–
Ex: Streptococcus: causes strep throat, if
untreated, the bacteria releases toxins causing
a rash known as scarlett fever.
Bacterial Diseases
Human Uses of Bacteria
• Food
– Bacteria are used to make cheese,
yogurt, buttermilk, sour cream,
pickles, sauerkraut and vinegar.
• Drugs (Medicines)
– Also used to synthesize drugs such as
insulin.
• Environmental Use
– Certain bacteria are used to digest
petroleum after an oil spill.
Controlling Bacteria
• Physical Removal
– hand washing removes bacteria
• Disinfectants
- chemicals that kill bacteria
• Food Storage –
- refrigeration/freezing slows the growth
• Food Procession
– boiling, frying, steaming kills bacteria
• Sterilization by Heat
– kills bacteria
Controlling Bacteria (Cont.)
• Vaccines – a preparation of weakened
or killed pathogen or inactivated toxin
- The vaccine stimulates the body to
produce immunity to a specific disease
• Antibiotics – block the growth and
reproduction of bacteria
- Disrupt proteins or cell processes specific
to bacterial cells
- Do not harm host’s cells
Superbugs
• Use of antibiotics has lead to
bacteria that are resistant to
antibiotics
– Penicillin killed many
infections in the 1940s when
it was introduced. Now is
has lost effectiveness
– Bacteria that are resistant to
penicillin reproduce and
pass resistance on through
conjugation
– MRSA – skin infection
spread
by close contact
Viruses
Viruses
• Virus
– Latin word for poison
– Viruses are particles of nucleic acid,
protein and sometimes lipids
– Not alive because they are not able to
reproduce independently
– Reproduce by entering living cells and
use the infected cell to produce more
viruses
Structure of Viruses
• Core
– A core of either DNA or RNA
• Capsid
– A protein coat that surrounds the core
– Has proteins that enable the virus to
enter cells
Viral Infections
• Viral Infection
– Occur when viruses bind to specific proteins
on the cell surface. Most viruses are very
specific to the cells they infect.
• Bacteriophages
– viruses that infect bacteria
Lytic Cycle
•
•
•
•
Virus enters the cell
Virus destroys host DNA
Uses the host cell to make copies of itself
Host cell lyses (bursts) soon after infection releasing virus
particles
Lysogenic Cycle
• Virus imbeds its DNA into the DNA of the
host cell and is replicated along with the
host cell’s DNA. The cell doesn’t lyse
right away.
• Prophage
–The viral DNA that is embedded in the host’s
DNA
Viruses and Disease
• Adenoviruses
– Naked viruses w/linear DNA
– Polio, measles, mumps, yellow fever, colds,
and flu
• Oncogenic Viruses
– Disrupt normal controls on cell growth
causing cancer.
• Retroviruses
– Usually RNA is copied from DNA, but in
retroviruses DNA is copied from the viral
RNA (Ex: AIDS)
RNA Viruses
• 70% of viruses have RNA instead of
DNA
• RNA viruses cause colds, AIDS,
cancer and others
The common cold
• The virus is brought in the host cell
(nose, etc.)
• The host cell makes viral protein
and RNA
• Within 8 hours the hose cell bursts
and releases hundreds of new
viruses
HIV
• HIV is a retrovirus – the genetic information is
copied from the RNA to DNA
• The viral DNA remains inactive for many cell
divisions
• When activated, the viruses damage the host’s
immune system.
VIRUSES vs. CELLS
• Viruses have many characteristics
of cells
• Viruses depend on living things and
therefore were not likely to be the
first living organisms.
New Viruses
• Genetic makeup of viruses
changes quickly and allows a
virus to jump form one
species to another.
- AIDS may have jumped
from nonhuman primates
- “Bird flu” is a concern
because it may jump to
humans and is similar to
some of the most deadly
human versions of the flu
Prions
• Prions
– particles that contain no DNA or RNA, only
proteins.
– Misfolded proteins that cause other proteins
to misfold.
• Examples
– Mad Cow Disease
– Scrapies
– TSE (Transgenic Spongiform Encephalitis)
• The human form of mad cow. Proteins that come
into contact with the prion unwind making holes in
the brain so that it looks like a sponge.
• How Prion's Kill
Protista
Protists
• Eukaryotes that don’t fit into the
plant, animal or fungi kingdoms.
• Most are unicellular but can be
multicellular
Movement
• Pseudopods
• Cilia
• Flagella
Reproduction
•
•
•
•
Asexually by mitosis
Sporangium
Conjugation
Sexual Reproduction
– Alternation of generations
Examples of Protists
• Amoeba
• Paramecium
• Euglena
Ecological Significance
• Parasites/Disease Causing Protists
– Causes harm to host organism
– Ex: Malaria
• Mutualists
– Lives within an organism
– Both organisms benefit
– Ex: Termites
Fungi
Fungi
• Fungi
– Heterotrophic
• Feeds on other
organisms
– Eukaryotic
– Cell Walls with
Chitin
Structure of Fungi
•
•
•
Fruiting Body
– Main structure
of the Fungi
– Reproductive
structure
Mycelium
– Mass of
branching
hyphae below
the soil
Hyphae
– Cells that are
long, slender
branching
filaments
– Make up both
the fruiting
body and the
mycelium
Life Cycle
• Spores
– Asexual form of reproduction, the
spores travel through air/water
• Sexual Reproduction
Significance of Fungi
• Parasites
– Ex: Ringworm
• Lichens
– Partnership of fungi
and algae
• Mycorrhizae
– Help feed plants