Chapter 17
Viruses & prokaryotes
17-1 Viruses
 What
 How
is a virus?
do viral life cycles differ?
 What
is the relationship between
viruses and their hosts?
What is a virus?
A
virus is a noncellular particle made
up of genetic material and protein
that can invade living cells
 First
discovered in 1935 by an
American scientist named Wendell
Stanley
 It
was called the tobacco mosaic
virus or TMV
TMV on tobacco plant
http://healthyhomegardening.com/Disease.php?pid=15
http://concerncrisis.blogspot.com/2008/03/tobacco-mosaic-virus-tmv.html
Structure of a virus
 Composed
of a core of DNA or RNA
surrounded by a protein coat called a
capsid
 Capsid
 The
protects the genetic material
core contains several genes to
several hundred genes
http://micro.magnet.fsu.edu/cells/virus.html
 More
complex structures are in
viruses called bacteriophages –
viruses that invade bacteria
 Has
a head region (capsid), a nucleic
acid core, and a tail
 Some
have tail fibers that allow them
to attach to the bacteria
http://micro.magnet.fsu.edu/cells/virus.html
 Viruses
are rod-shaped, tadpoleshaped, helical and cubelike shaped
 Vary
in size from 20 to 400
nanometers
A
nanometer is one billionth of a
meter
http://learnsomescience.com/microbiology/viruses-viroids-and-prions/
Specificity of a virus
 Specific
viruses infect specific
organisms
 Plant
virus cannot infect an animal
 Only
mammal viruses that do not
infect other animals and vise versa
 Viruses
for every type of organism
http://www.wellesley.edu/Chemistry/Chem101/dna-viruses/viruses.html
Life cycle of a Lytic Virus
 In
order to reproduce, viruses must
invade, or infect, a living host cell
 They
 One
also invade in different ways…
way is done by lytic viruses
where when they invade the cell
bursts or lyses
Life cycle of a lytic virus
http://dvm5.blogspot.com/2010/11/classification-of-viruses.html
Infection
A
virus is activated by contact with
the right host cell (chance)
 It
then injects its DNA into the cell
Life cycle of a lytic virus
http://dvm5.blogspot.com/2010/11/classification-of-viruses.html
Growth
 The
RNA polymerase of the host cell
creates messenger RNA of the virus
DNA
 This
cell
mRNA then takes over the host
 Some
proteins turn off the creation
of molecules for the cell
Life cycle of a lytic virus
http://dvm5.blogspot.com/2010/11/classification-of-viruses.html
Replication
 It
then uses the host cell to make
thousands of copies of its own
protein coat and DNA
 The
host cell is then filled with viral
DNA molecules
 These
three steps can happen in 25
minutes
Life cycle of a lytic virus
http://dvm5.blogspot.com/2010/11/classification-of-viruses.html
 The
infected cell then lyses (bursts)
and releases hundreds of virus
particles
 These
 The
particles than infect other cells
host cell is lysed and destroyed
so this process is called lytic
infection
http://en.wikipedia.org/wiki/Lytic_cycle
Lysogenic Infection
 Lysogenic
infection-the virus does
not reproduce and lyse its host cell
 The
DNA of the virus enters the cell
and is inserted into the DNA of the
host cell
 The
viral DNA is then known as a
prophage
Prophage activity
 Blocks
entry of other viruses and
may even add useful DNA to the host
cell’s DNA
 Eventually
it will remove itself from
the DNA and create new virus
particles
http://en.wikipedia.org/wiki/Lytic_cycle
Retroviruses
 Retroviruses
contain RNA as their
genetic information
 When
they enter the cell they
produce a DNA copy
 This
DNA
then enters into the host cells
http://ucdbiotech.wordpress.com/2009/10/13/be-on-the-alert-the-first-ever-gammaretrovirus-capable-of-infecting-human-hosts-has-been-identified
/
Viruses and Living Cells
 Viruses
must infect living cells to
carry out their functions
 Viruses
are parasites-an organism
that depends entirely upon another
living organism for its existence in
such a way that it harms that
organism
http://westernrifleshooters.blogspot.com/2011/02/interview-with-stanley-kurtz.html
Are viruses alive?
 Viruses
are not made of cells
 They
can grow, reproduce, regulate
gene expression, an evolve
 It
is up for debate
Virus video
17-2 Prokaryotic Cells
Bacteria Intro
video
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/cellprokaryote6.gif
Prokaryotes
 Cells
that do not have a nucleus
http://en.wikipedia.org/wiki/Prokaryote
Eubacteria
http://calexa.weebly.com/eubacteria.html
Cyanobacteria
http://user.uni-frankfurt.de/~schauder/cyanos/cyanos.html
Archaeabacteria
 Methanogens
– archaeabacteria that
produces methane gas
http://en.wikipedia.org/wiki/Archaea
Prochlorobacteria
http://jk169.k12.sd.us/proteobacteria.htm
Bacteria (E. Coli)
 One-celled
http://en.wikipedia.org/wiki/Bacteria
prokaryotes
They do not contain the complex range of
membrane enclosed organelles that are
found in most eukaryotic cells
http://www.weblife.org/humanure/images/fig3-1.jpg
Eubacteria Structure
– generally surrounded by a cell wall
made of carbohydrates
– there is a cell membrane which
surrounds the cytoplasm
– long whip like flagella protrude
from the membrane through the
cell wall
Eubacteria
http://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Average_prokaryote_cell-_en.svg/494px-Average_prokaryote_cell-_en.svg.png
They use photosynthesis to get
energy
http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT311/Cyanobacteria/CyanoHyellaStella300Crop.jpg
Fresh and saltwater, land, hot
water, arctic, grow on snow
http://lyxia.us/wp-content/uploads/2012/08/cyanobacteria-1.jpg
Methanogens are archaebactria
that produce methane gas
http://www.daviddarling.info/images/methanogens_large.jpg
prochlorobacteria more related
to chloroplasts
http://jk169.k12.sd.us/images/Escherichia_coli1355024.300a[1].jpg
Bacteria Identification
– cell shape
– Cell Wall
– Bacterial Movement
– How the obtain energy
Bacterial shape
https://benchprep.com/blog/ap-biology-diversity-of-organisms-kingdoms-part-i/
Gram Staining
 There
are two types of dye, The
bacterial cells with only one thick
layer of carbohydrate and protein
molecules outside the cell membrane
took up the crystal violet. The
bacterial cells that have lipid and
carbohydrate molecules appear red
under the microscope and are gram
negative
Gram Staining
http://en.wikipedia.org/wiki/Gram_staining
Bacterial movement
– propelled by flagella
– spiral forward
– glide slowly
http://upload.wikimedia.org/wikipedia/commons/thumb/1/15/Flagellum_base_diagram_en.svg/629px-Flagellum_base_diagram_en.svg.png




Phototrophic autotrophs-prokaryotes
that trap the energy of sunlight
Chemotrophic autotrophs-prokaryotes
that live in harsh environments and obtain
E from inorganic molecules
Chemotrophic heterotrophs-bacteria
that obtain energy by taking in organic
molecules and then breaking them down
and absorbing them
Phototrophic heterotrophs- use
sunlight for Energy but also need organic
compounds for nutrients
Obligate aerobes (tuberculosis)
 Require
oxygen
http://www.news-medical.net/health/What-is-Tuberculosis.aspx
Obligate anaerobes (Clostridium
botulinum)
 Bacteria
that do not require oxygen
http://www.agefotostock.com/en/Stock-Images/Rights-Managed/BSI-0217005
Toxins
 Poisons
that can cause botulism
which is a rare form of food
poisoning (paralysis)
http://www.sciencedaily.com/releases/2008/06/080616115718.htm
Facultative anaerobes
(Gardnerella)
 Bacteria
that can survive with or
without oxygen
http://www.redorbit.com/education/reference_library/health_1/bacteria/2584148/gardnerella/
Binary Fission
 Bacterial
cell replicates its DNA and
divides in half (asexual reproduction)
http://biology.about.com/od/cellanatomy/ss/prokaryotes_2.htm
Conjugation
 Genetic
information from one
bacteria is transferred to the other
(sexual reproduction)
http://partsregistry.org/Conjugation
Endospore

Spore formed when a bacterium produces
a thick internal wall that encloses its DNA
and portion of its cytoplasm (Not
reproduction)
http://en.wikipedia.org/wiki/File:Electron_micrograph_of_endospore_of_the_bacterium_Carboxydothermus_hydrogenoformans.png
Bacteria food production
http://www.jgi.doe.gov/News/news_10_17_06.html
Symbiotic relationship (E. Coli)
 Both
organisms benefit
http://blog.search-mojo.com/2010/10/26/googles-symbiotic-relationship-with-seos-yeah-right/
They are able to break down cellulose
due to the bacteria that make enzymes
that allow animals to digest cellulose
http://www.quia.com/files/quia/users/lmcgee/biochemistry/cellulose-cows.gif
They recycle and decompose, or
break down dead material
Saprophyte bacteria
 Bacteria
that digest organic matter
and break it down to simpler
substances
http://www.apsnet.org/edcenter/intropp/lessons/prokaryotes/Pages/BacterialBlotch.aspx
Bacteria sewage decomposition
http://healthnews-younis.blogspot.com/2010/12/turning-up-heat-on-antibiotic-resistant.html
Nitrogen Fixation (Rhizobium)
http://textbookofbacteriology.net/Impact_2.html
17-3 Diseases Caused by Viruses
and Prokaryotes
 Only
a small number of viruses and
prokaryotes are capable of disease in
humans
 Pathogens-disease
agents
 Its
producing
basically a battle for nutrients
between the host cell and the
microorganism
Pathogens
http://www.beltina.org/health-dictionary/pathogen-definition-what-is.html
Viruses and Disease



Viruses are the cause of such human
diseases as small pox, polio, measles,
AIDS, mumps, influenza, yellow fever,
rabies, and the common cold
Caused from the virus life cycle
The only successful protection against
them is preventing their infection
 The
immune system must be
stimulated to prevent the infection
 They
stimulate them with vaccines
which inject a weakened or killed
disease causing virus
 Once
a viral infection starts, there is
little science can do to stop the
disease
 They
mainly treat the symptoms
Vaccines
http://www.fbresearch.org/TwoColumnWireframe.aspx?pageid=123
Interferons
 These
are small proteins that are
produced by the body’s cells when
the cells are infected by viruses
 Seem
to make it more difficult for
the virus to spread
 Could
be used to fight viruses
Interferons
http://www.odec.ca/projects/2007/sank7b2/page7.html
Cancer




Some viruses cause cancer in animals
called oncogenic viruses
Virus adds certain genes to the cell to
make it a cancer cell
Not very common
The Rous Sarcoma Virus (RSV) is an
example in chickens
Rous Sarcoma Virus
http://dict.youdao.com/w/rous_sarcoma_virus/#q%3Drous_sarcoma_virus
Bacteria and Disease
 Only
a few bacteria produce diseases
 Some
of the diseases caused by
pathogenic bacteria include
diphtheria, tuberculosis, typhoid
fever, tetanus, leprosy, syphilis,
cholera, and bubonic plague
Bacterial Diseases
http://en.wikipedia.org/wiki/Bacteria
 Cause
disease in two general ways:
– May damage the cells and tissues of
infected organisms directly by breaking
down its living cells to use for food
– May release toxins that travel
throughout the body, interfering with
the host
 Many
diseases can be prevented by
stimulating the immune system as
well
 There
are also many other ways to
fight against bacteria once infected
 One
is drugs and natural compounds,
known as antibiotics, that attack
and destroy bacteria
 This
has increased life expectancy
over the last two centuries
Antibiotics
http://www.nlm.nih.gov/medlineplus/antibiotics.html
Controlling Bacteria: Sterilization
 Sterilization
destroys living bacteria
with great heat or chemicals
 Bacteria
cannot survive high temps
so most can be killed boiling water
 Disinfectants
are another good way
to sterilize many places
Sterilization
http://preparednesspro.wordpress.com/2009/08/11/myths-and-facts-ofwater-storage/water-storage-myths-boiling-water/
http://ykalaska.wordpress.com/2006/05/03/disinfectants-for-camp-field-and-household/
Food Processing
 Bacteria
are everywhere including in
our food (if we don’t eat it they will
which spoils it)
 Refrigeration
grow as fast
 Many
causes bacteria to not
foods are sterilized by boiling,
frying, or steaming (kills bacteria
Food Spoilage
http://chefsblade.monster.com/training/articles/221-a-guide-to-food-pathogens
 Food
that is properly canned will last
pretty much indefinitely
 Chemical
treatments such as salt,
vinegar, or sugar also preserve the
food
 Examples:
salted meat, pickled
vegetables, and jam
Canning
http://www.foodinjars.com/2011/08/canning-101-tomato-float-sauce-separation-and-loss-of-liquid/