Transcript Chapter 22 PowerPoint Lecture Notes

Bacteria and Viruses
Chapter 22
Mountain Pointe High School
R. LeBlanc, M.S.
How small is life?
100 µm
20 µm
•What does um represent?
•What do the yellow structures represent and how did they get there?
•How large are these bacillus bacterial cells?
0.5 µm
bacteriophage
ruptured bacterial cell
•Can you see the
bacteria?
•What are
bacteriophage?
•Which are
larger, virus or
bacteria? How
much smaller?
•Are these viruses
living? Why or
why not?
Fig. 22.2, p. 355
1.5 µm
Characteristics of Bacteria
 Metabolic Diversity
Photoautotrophic (Energy from: CO2; H2O; H2; H2S)
Chemoautotrophic(Energy from: CO2; H2; S; NH4)
Photoheterotrophs (carbon source=fatty acids; carbs)
Chemoheterotrophic (parasites or saprobes)
 Sizes and Shapes (all of these are unicellular)
1 - 10 micrometers
Coccus
Bacillus
Spirillum
What is the difference between an autotroph and heterotroph?
coccus
bacillus
Small staffs maybe
skiny or fat
Sometimes oval &
flattened
spirillum
One or more twist; some like a comma; flexible or stiff
corkscrews
in-text, p. 356
Characteristics of Bacteria
Structures
Cell walls
Peptidoglycan
(molecules of polysaccharide cross
linked with short polypeptides)
Membrane (some membrane compartments:
plasma)
Characteristics of Bacteria
Glycocalyx (mesh that encloses wall; called
capsule)
DNA in cytoplasm (not membrane bound)
Flagella (movement; one or more; whip like)
Gram stain (use to ID bacteria: refer to other slide)
0.5 µm
1 µm
•H. pylori with its
many flagella
•Bacilli & coccus
bacteria attached to
human teeth. (Are
these bacteria
harmful?)
•Pathogenic
bacteria
•Found in: water,
food, esp.
unpasteurized
milk. Fig. 22.4, p. 357
•E. coli dividing; Pilifilament projections
0.5 µm
Bacterial Structure
Pili are protein
filaments that help
bacteria to adhere to
surfaces; aids in
conjugation (sexual
reproduction)
The Proper Techniques Used in
Gram Staining Bacteria
Proper Gram Staining Procedures:
stain with purple dye
stain with iodine
wash with alcohol
counterstain with safranin
1.
Collect bacterial sample and carefully
heat-fix cells to microscope slide.
2.
Add Crystal Violet, a purple dye, to the
bacterial sample turning all cells purple.
3.
Then add iodine, a binding agent, that
causes the purple dye to stick to the gram
positive bacterial cells.
4.
Use an alcohol wash to rinse off the
purple dye from the gram negative cells
making them neutral in color.
5.
Last, counter-stain the bacterial sample
with safranin, a pink dye, that will stick to
the gram negative cells turning them pink.
Gram Positive: bacteria cells purple.
Gram Negative: bacteria cells pink with
counter stain.
Prokaryotic Fission
•When nearly doubled in size, it divides; 10-30 minutes.
•In some cases budding takes place; daughter cell buds off parent cell
•NOTICE: Cell synthesizes protein & lipid molecules causing the
plasma membrane to grow moving the 2 DNA molecules apart.
•Original DNA is a single circular chromosome thread.
a Bacterium (cutaway view)
before DNA replication. The
bacterial chromosome is
attached to the plasma
membrane.
b DNA replication starts. It
proceeds in two directions
away from the same site in
the bacterial chromosome.
c The new copy of DNA is
attached at a membrane site
near the attachment site of
the parent DNA molecule.
d New membrane grows
between the two attachment
sites. As it increases, it moves
the two DNA molecules apart.
e At the cell midsection,
deposits of new membrane
and new wall material extend
down into the cytoplasm.
f The ongoing, organized
deposition of membrane and wall
material at the cell midsection
divides the cell in two
IDENTICAL DAUGHTER
CELLS.
Fig. 22.7, p. 358
BACTERIAL CONJUGATION
nicked plasmid
conjugation tube
a A conjugation tube has already formed between
a donor and a recipient cell. An enzyme has nicked
the donor’s plasmid.
Plasmid: a small self-replicating circle of
extra DNA & has few genes.
c In the recipient cell, replication starts on the
transferred DNA.
b DNA replication starts on the nicked plasmid.
The displaced DNA strand moves through the tube
and enters the recipient cell.
http://www.hhmi.org/biointeractive/animatio
ns/conjugation/conj_frames.htm
d The cells separate from each other; the plasmids
circularize.
GENETICALLY IDENTICAL DAUGHTER CELLS.
•Conjugation: the transfer of DNA from one cell to another.
•Takes place in Salmonella; streptococcus & E. coli bacteria
Bacterial Classification
Numerical taxonomy
 Bacteria are not well represented in the fossil record.
 Traits of unidentified bacterial cells are compared to known
bacteria.
 Traits include: cell shape, motility, staining attributes,
nutritional requirements, metabolic patterns, endospores or
not?
Gene sequencing and comparative biochemistry
are used today in classifying.
 Especially using rRNA
 Small rRNA changes can be measured & used to relate some
groups.
 Newest technique to ID bacteria; nucleotide sequencing
eu= ‘typical’
EUBACTERIA
Live in harsh conditions
With distinct defined
organelles
ARCHAEBACTERIA
EUKARYOTES
•The definition of ‘species’ that fits sexually reproducing
organisms dos NOT fit bacteria.
•The term ‘strain’ is used to show minor differences between
bacteria that are closely related.
Archaebacteria
1st living cells; no peptidoglycan in cell walls; found in unusual
places.
Methanogens (“methane-makers”)
Swamps, sewage, mud, & animal guts.
Make ATP anaerobically: CO2 to CH4
Halophiles (“salt-lovers”)
Brackish ponds, salt lakes, hydrothermal
seafloor vents
Extreme Thermophiles (“heat-lovers”)
Acidic soils, hot springs, coal mines,
hydrothermal vents
•Methano-coccus
•Heat-loving and
methane producer
Methanogen with thick
polysaccharide walls called
peptidoglycan.
Which major archaebacteria group is represented below????
Cows belch producing a unique smell. Great Salt Lake; Which bacteria live there?
Commercial seawater evaporating
ponds. Hypersaline condition.
Hot, sulfur-rich water in Emerald
Pond, Yellowstone National Park.
Eubacteria
NOTE: They have fatty
acids incorporated into
their plasma membrane.
Photoautotrophic
Cyanobacteria (blue green algae)
Ponds and freshwater (see next slide)
Chemoautotrophic
Environment
Cycling of N2 , S2
Building blocks of amino acids (proteins)
Without nitrogen there would be NO LIFE.
Plants use nitrogen fixing bacteria to recycle nitrogen.
Eubacteria
Chemoheterotrophic
Most bacteria fall into this category.
Pseudomonads (decompose organic
even pesticides
Lactobacillus (‘good’ bacteria; making
pickles, yogurt, buttermilk; sauerkraut)
E. Coli (produce vitamin K/other
compounds)
Pathogenic (Disease causing; some E.
Coli; Botolinum
Endospores (Tetanus found in the soil)
Cyanobacteria
•Nutrient rich pond
•Heterocyst: modified
cells that form when
nitrogen compounds
are scarce; make a
nitrogen-fixing enzyme
resting spore
heterocyst
5 µm
developing endospore (Resting structure)
2.2 µm
•Triggered by the depletion of nitrogen or other nutrients.
•When plasma membrane breaks it releases many free spores.
•Can remain dormant for decades.
•When conditions are favorable they become active as a bacterial cell.
Facts About Bacteria
Also classified by their arrangements. Some
exist alone, most are grouped together:
 Diplo - paired cells
 Staphylo - clustered cells
 Strepto - cells in chains
What causes
this
condition?
Rocky
Mountain
Spotted
Fever
•Moves from host to host inside the gut of insect (tick) as bacteria.
•Penetrates the cytoplasm & nucleus of host cells.
•Lyme Disease: transmitted from deer ticks.
Different examples of bacterial infections
Match the picture with the bacterial infection: A) LEPROSY
B) LYME DISEASE C) PINK EYE D) ATHELETES FEET
0.25 µm
Magnetotactic
Bacterium
Myxobacteria with fruiting
bodies
Viruses,
Viruses,
and
Viruses
The Viruses
 Non-cellular infectious agent
 Infect: cats, cattle, birds, insects, plants, fungus, protist,
& bacteria (can infect organisms in ALL kingdoms).
 Protein coat surrounding a nucleic acids core
 Rod-like or polyhedral shapes
 Used for protection, shape can change, used to attach to
host cells (attach to proteins in plasma membrane of
host.
 DNA or RNA
 Reproduce inside a host cell
 Enveloped or non-enveloped
viral RNA
protein subunits of coat
Polyhedral
Virus
•Tobacco Mosaic Virus
•Helical Virus
18-nm diameter,
250-nm length
80-nm diameter
lipid envelope;
proteins span the
envelope, line its
inner surface,
and spike out
above it
DNA
protein coat
sheath
viral RNA
base plate
tail fiber
reverse transcriptase
viral coat (proteins)
100-120 nm diameter
65-nm diameter head,
225-nm total length
Fig. 22.16, p. 364
Viruses
Shape
Helical (Rod Shaped)
Polyhedral
Enveloped or nonenveloped
Spiked (some)
Complex
Viruses are host specific
Bacteriophages
Used to study viruses
Reproduce rapidly
Polyhedral Virus
Viruses
Bacteriophage
Infects bacteria
Used in early
experiments to
determine function of
DNA
Viruses
Enveloped virus
Envelope is made
mostly of membrane
remnents from
previously infected
cell
HIV is example
 Trigger for AIDS
 Attacks certain W.B.C.
 Weakens immune
system
Infectious Agents
Tinier Than Viruses
(more stripped down than viruses)
 Prions (8 rare diseases of nervous system)
 Small Proteins
 Altered products of a gene found at the surface of neurons of
nervous system.
 Mad Cow Disease (BSE)*
 Diseases
 Kuru (brain)
 Scrapie (sheep); named after sheep scrape off their wool.
 Creutzfeldt-Jakob disease (destroys muscle & brain function)
*Outbreak in 1996. Caused by ground up sheep with Scrapie where feed to cattle
in turn spread to cattle, then to humans.
Infectious Agents
Tinier Than Viruses
Viroids
Tight folds or circles of RNA
Plant diseases
Destroy million of $ of:
• Potatoes
• Citrus
• Other cash crops.
Viral Multiplication Cycles
5 Steps
Attachment
Penetration
Replication
Assembly
Release
Lytic pathway
Host cell lysis
Lysogenic pathway
Viral DNA
integrates into
bacterial
chromosome
Lytic Cycle
The Lysogenic Cycle
Multiplication Cycle of a
Bacteriophage Virus
In Conclusion
 After the origin of life, a divergence
occurred leading to Eubacteria and
common ancestors of Archaebacteria and
Eukaryotic cells
 All bacteria are prokaryotes
 Bacteria have 3 basic shapes: cocci, bacilli,
and spirilla
In Conclusion
 Many bacteria have external structures
that increase their survival and
pathogenicity
 Bacteria reproduce by binary fission
 Many species have plasmids and some can
transfer genetic information through the
process of conjugation
 Bacteria as a group have metabolic
diversity
In Conclusion
 Viruses are nonliving infectious agents
 Viruses consist of either DNA or RNA
surrounded by a protein coat
 Some may have an envelope and spikes
 Viruses cannot reproduce on their own but
must use a host cell’s machinery
 There are five steps in the multiplication
cycle of a virus
In Conclusion
 There are two pathways common in the
multiplication of bacteriophages: lytic and
lysogenic
 Multiplication cycles of viruses are diverse;
may occur rapidly or can enter a latent
phase

developed by M. Roig