Download Gram-negative bacteria

Bacteria
Prokaryotes are the most
numerous organisms on
Earth
Prokaryotes
Prokaryotes: are single-celled
organisms that do not have a
membrane-bound nucleus
 They live in every environment on Earth
 They are a major source of food for
many organisms
 They also help many organisms digest
food

General Characteristics
1.
2.
3.
4.
5.
6.
Unicellular
Prokaryotic
Nutrition modes: mainly absorption,
some photosynthetic, some
chemosynthetic
Anaerobic and aerobic species
Reproduction: fission or budding
microscopic
Carl Woese

Discovered in the
late 1970’s that
prokaryotes made
up 2 of the 3
domains of life
 Categorized based
on ribosomal RNA
analysis
2 Major Domains
1.
2.
Archaea: means “archaic” or “ancient”
Bacteria:
Domain Archaea

Not like bacteria, but more like Eukaryota
 Differ from bacteria in the make up of their
cell wall, membrane lipids, their genetics &
metabolism
 Cell walls do not have peptidoglycan (a
protein-carbohydrate compound)
 Cell walls have different amino acids and
different types of lipids
Truth about Archaea

Archaea were first discovered in extreme
environments like swamps, salt lakes and hot
springs
 Recently, scientists found Archaea genetic
materials in samples of surface water from
the North Pacific & Antarctic Oceans
 So, Archaea may be more common that once
thought.
3 Broad Groups of Archael
Bacteria
1.
2.
3.
Methanogens
Halophiles
Thermoacidophiles
1. Methanogens

Named for their unique way of getting
energy
– Convert H2 gas & CO2 into methane gas (CH4)

Live in anaerobic environments)-like
swamp bottoms (marsh gas), sewage,
intestinal tracts of humans, cows, &
termites
 Oxygen is poisonous to them
A cow can belch 200 & 400 L
Of Methane per day
The methane that bubbles out at marshes are called marsh gas
2. Halophiles
“Salt Lovers”-live in high salt
concentrations like the Great Salt Lakes
& Dead Sea
 High salt concentrations would kill most
bacteria but favor the growth of
halophiles b/c they have adapted to live
in very salty water
 Aerobic organisms

• Ex: Salt Lakes
• Ex: Dead Sea
3. Thermoacidophiles
Live in very acidic environments that
have very high temperatures (ph less
than 2) with temperatures (230 F);
 Found in hot springs (Yellowstone
National Park), volcanic vents,
hydrothermal vents of the ocean
 Requires sulfur
 anaerobes


Hot Springs at Yellow
Stone National Park
• Hydrothermal Vent
Domain Bacteria
Most well known prokaryotes
 General Characteristics
1. Largest group of bacteria
2. Occur in many shapes and sizes
3. Have distinct biochemical and genetic
characteristics

Domain Bacteria

Occur in different shapes and sizes
 Identified by basic shapes
1. Sphere: Coccus [round]
2. Rods: Bacillus [Rod Shaped]
3. Spirals: Spirillum [Spiral]
Three Bacterial Cell Shapes
Bacterial cells are also classified
by their arrangements

Diplo – Two
Bacteria can occur in pairs
diplo- bacilli or cocci

Staphlyo – Clusters
Staphylococci cause
“staph” infections

Strepto – Long
Chain
Streptococcus cause infections
such as “strep” throat
Some well known Bacteria
Streptococcus mutans causes tooth decay by converting
sugars to an acid
That erodes the tooth
Clostridium botulinum produces a poison causing food
poisoning
Treponema pallidum causes syphilis
Gram Stain
Used to group bacteria into 2 groups
based on the structure of their cell walls
 1. Gram-positive bacteria: appears
purple because they retain the crystal
violet stain



Are simpler and have more peptidoglycan
The stain retains purple dye and appear purple
Gram-negative bacteria

2. Gram-negative bacteria: appears pink
because the cell becomes
counterstained by the safranin red stain

Gram negative bacteria have cell walls that are
complex and have small amounts of peptidoglycan
It takes up the red dye of the Gram stain making it
look pink

Peptidoglycan
Cell Wall
Peptidoglycan
Cell Wall
Important Bacterial Groups
5 major phyla (actually 12 phyla exist)
1. Cyanobacteria
 2. Spirochetes
 3. Gram-Positive Bacteria
 4. Proteobacteria
 5. Chlamydia

Important Bacterial Groups
5 major phyla (actually 12 phyla exist)


1. Phylum Cyanobacteria:
(blue green bacteria)
 Photosynthestic
 Encased in a jelly like substance-live in
colonies
 Some are made of chains of cells with special
enlarged cells called heterocysts (fixes
nitrogen into ammonia which plants use)

Environmental note: Anabaena loves
phosphates and nitrates-undergoes a
population bloom (eutrophication)-following
the bloom many die and become
decomposed by heterotrophic bacteria which
consume large amounts of oxygen causing
fish kills
Important Bacterial Groups
5 major phyla (actually 12 phyla exist)
 2. Phylum Spirochetes:
 Gram negative, spiral-shaped bacteria
 Some are aerobic, some anaerobic
 Moves by means of a cork-screw like rotation
 Live freely, symbiotically, or as parasites
 Treponema pallidum causes syphilis
 Borrelia burgdorferi causes limes disease
Important Bacterial Groups
5 major phyla (actually 12 phyla exist)

3. Phylum Gram Positive Bacteria

Not all are gram positive
Some gram negative in this group share
molecular similarities
Makes yogurt
Found in oral cavity and human intestines
Causes tooth decay
Makes antibiotics (actinomycetes)





Members include:
streptococcal species, causes strep
throat
 Clostridium botulinum: makes toxins in
botulism (used medically to treat painful
muscle spasms and frown lines on the
face)
 Anthrax is caused by the rod Bacillus
anthracis which is used as a biological
weapon

Important Bacterial Groups
5 major phyla (actually 12 phyla exist)

4. Phylum Proteobacteria:
 Largest & most diverse bacteria
 Divided into several subdivisions:
 A. Enteric Bacteria
– Gram negative, heterotrophic, found in animal
intestinal tracts, aerobic or anaerobic, Escherichia
coli (E.coli) found in human intestines; makes
vitamin K, aids in the break down of nutrients,
Salmonella-disease causing protobacteria

B. Chemoautotrophs:
– Gram negative, extracts energy from minerals
– Lives symbiotically
– Rhizobium and Azotobacter-fix nitrogen in the
soil. Live in nodules inside the roots of legumes
which is important to the success of plants
– Called Nitrogen Fixation

C. Other Proteobacteria:
– Some cause disease like Rocky Mountain
Spotted Fever
– Helicobacter plyori causes stomach
ulcers
– Agrobacterium causes tumors in plants
Important Bacterial Groups
5 major phyla (actually 12 phyla exist)
5. Chlamydia
 Gram-negative-coccoid bacteria
 Live only inside animal cells (rely for
protection and nutrients)
 The cell walls do not have
peptidoglycan
 Chlamydia tramchomatis causes
chlamydia---an STD

The importance of bacteria

Soybeans have nodules
on their roots that convert
nitrogen gas to ammonia
that is used by the plant

Foods & Medicines
some foods would not
exist without bacteria
Swiss cheese
Distinctive flavors
Nitrogen fixing
bacteria
vinegar
Crispy
Pickles
sauerkraut
Biology of Prokaryotes
Structure & Function
Nutrition & Metabolism
Prokaryotes have many ways of getting carbon and
energy from the environment
Heterotroph
Photoheterotroph
Chemoheterotroph
Uses light energy but gets its
carbon from other organisms
Obtains both energy and carbon
from other organisms
Autotrophs
Photoautotroph
Uses light energy and gets carbon
from CO2
Chemoautotroph
Extracts energy from inorganic
compounds and uses CO2 as a
carbon source
Reproduction: binary fission

Prokaryotes
reproduce
asexually by
binary fission
ANTIBIOTICS

Antibiotics affect bacteria with certain cellular
activities
– Penicillin: blocks the ability to build new cell wall
material
– Tetracycline: blocks protein synthesis

Antibiotics are made naturally by some fungi
& bacteria
 They kill neighboring bacteria or fungi that
compete for resources
Antibiotic Resistance
A big worry for modern medicine
 Bacteria may become resistant to
antibiotics by

– Mutations in bacterial DNA give bacterium
resistance
– Mutant bacteria multiply & take over the
population and stop the antibiotic’s curing
power
Viruses
In 2003, some people in China started showing
symptoms of a new illness. These symptoms were
similar to those of pneumonia. The condition was
highly infectious. Soon, scientists found that the
disease was caused by a virus. They called the
disease severe acute respiratory syndrome, or SARS
What is a Virus?

You’ve probably had the
flu—influenza—at some time
during your life.



Nonliving particles called
viruses cause influenza.
Viruses are composed
of nucleic acids
enclosed in a protein
coat and are smaller
than the smallest
bacterium
Viruses are interesting
to scientists because
they cause many
diseases and are useful
tools for genetic
research
Did You Know…

Viruses are not alive because they lack
some of the key characteristics of living
organisms
– 1. They do not have cytoplasm or organelles
– 2. They cannot carry out cellular functions like
metabolism and homeostasis
– 3. They do not grow as cells do by dividing into two
– 4. They cannot reproduce outside a host cell
– 5. They must enter a living cell and use the host cell’s
ribosomes, ATP, enzymes, and other molecules to
reproduce
Virus Size and Structure
Viruses are some of the smallest
particles that are able to cause disease
 They vary in size and shape

Capsids and Envelopes
A capsid is the protein shell that
encloses the viral genome
 Capsids are built from protein subunits
called capsomeres
 A capsid can have various structures

Viral Shapes

Consist of an inner core
of nucleic acid
surrounded by 1 or 2
protein coats or capsid
 The human flu virus
may have another layer
called a viral envelope
surrounded by an outercoat
 Contains DNA & RNA
but never both
The arrangement of
proteins give different
shapes to viruses
RNA
Capsomere
DNA
Membranous
envelope
RNA
Capsid
Head
Capsomere
of capsid
DNA
Tail
sheath
Tail
fiber
Glycoprotein
18  250 nm
70–90 nm (diameter)
20 nm
50 nm
(a) Tobacco mosaic
(b) Adenoviruses
virus
Glycoproteins
80–200 nm (diameter)
50 nm
(c) Influenza viruses
80  225 nm
50 nm
(d) Bacteriophage T4
Shapes

Polyhedral viruses
(polio virus)
resembles small
crystals
 Tobacco mosaic
viruses-small
cylinders
 T-4 –looks like a lunar
landing module
Nucleic acid
Capsid
Viral Envelopes
Some viruses have membranous
envelopes that help them infect hosts
 These viral envelopes are derived from
the host cell’s membrane and contain a
combination of viral and host cell
molecules


The envelope is formed
from the nuclear
membrane or the cell
membrane of the host cell
as the viral capsid buds
from the host cell
Classification of Viruses
1.
2.
By whether they have RNA or DNA as their
gnome and whether their gnome is double
stranded or linear or circular.
Based on the nature of the capsid and on
the presence or absence of an envelope
ex: SARS is a coronavirus. Corona is the
Latin word for “crown” –the envelope protein
looks like a crown
How are they named?

Viruses are not
given names
 1. Often named
after the disease
they cause
EXAMPLE: RABIES
VIRUS

Poliovirus

AIDS VIRUS
How are they named?

3. Code Numbers are
 2. The organ or
used to name several
tissue they infect
viruses infecting the
EXAMPLE:
same host
ADENOVIRUSES  Example: T-1  T-7
adenoid tissue in the
7 viruses that infect
back of the throat
the intestinal bacteria
E.coli (T stands for
Type)
Bacteriophage
Bacteriophages, also called phages,
are viruses that infect bacteria
 They have the most complex capsids
found among viruses
 Phages have an elongated capsid head
that encloses their DNA
 A protein tail piece attaches the phage
to the host and injects the phage DNA
inside

T-4

Bacteriophage is a
virus that infects
bacteria T-4
Attachment to a Host


Before a virus can
replicate, it must enter a
host cell
virus recognizes and
attaches to a host cell
when one of its proteins
interlocks with a
molecular shape that is
the receptor site on the
host cell’s plasma
membrane.
General Features of Viral Cycles
Once a virus has entered a cell, it
begins to manufacture viral proteins
 The virus makes use of host enzymes,
ribosomes, tRNAs, amino acids, ATP,
and other molecules
 Viral nucleic acid molecules and
capsomeres spontaneously selfassemble into new viruses
 These exit from the host cell, usually
damaging or destroying it

DNA
1 Entry and
uncoating
VIRUS
3 Transcription and
Capsid
2 Replication
manufacture of
capsid proteins
HOST
CELL
Viral DNA
mRNA
Viral DNA
Capsid
proteins
4 Self-assembly of
new virus particles
and their exit from
the cell
Replicative Cycles of Phages
Phages are the best understood of all
viruses
 Phages have two reproductive
mechanisms: the lytic cycle and the
lysogenic cycle

The Lytic Cycle

The lytic cycle is a phage replication
cycle that ends in the death of the host
cell

The lytic cycle produces new phages
and lyses (breaks open) the host’s cell
wall, releasing the progeny viruses
– A phage that reproduces only by the lytic
cycle is called a virulent phage
– Bacteria have defenses against phages,
including restriction enzymes that
recognize and cut up certain phage DNA
Lytic Cycle: To Break Down
1. Attachment
4. Assembly: nucleic
2. Entry: once inside
acid & coats are
the virus destroys
assembled into new
the host DNA
viruses
3. Replication: it
5. Release: host cell
reprograms the cells
breaks open & new
metabolic activity to
virus
particles
are
copy the virus genes
released
1 Attachment
2 Entry of phage
5 Release
DNA and
degradation
of host DNA
Phage assembly
4 Assembly
Head
Tail
Tail
fibers
3 Synthesis of
viral genomes
and proteins
The Lysogenic Cycle
The lysogenic cycle replicates the phage
genome without destroying the host
 Phages that use both the lytic and
lysogenic cycles are called temperate
phages
 The viral DNA molecule is incorporated
into the host cell’s chromosome
 This integrated viral DNA is known as a
prophage

Lysogenic Cycle
1.
2.
3.
Begins like the Lytic
Cycle
Instead of destroying
the host cell the DNA
becomes part of the
host
New DNA does not
interfere with normal
functions of the host
cell
4. Every time the host
cell reproduces,
virus is reproduced
5. Can continue
undetected for many
years, but can pop
out at any time then
the virus starts
killing the host cells.
Replicative Cycles of Animal
Viruses

There are two key variables used to
classify viruses that infect animals
– 1. The nature of the virus (single- or
double- stranded DNA or RNA)
– 2. The presence or absence of an
envelope
• An animal virus with an envelope uses it to
enter the host cell
RNA -Retrovirus
The broadest variety of RNA genomes
is found in viruses that infect animals
 Retroviruses use reverse
transcriptase to copy their RNA
genome into DNA
 HIV (human immunodeficiency virus) is
the retrovirus that causes AIDS
(acquired immunodeficiency syndrome)

Provirus-DNA
Viral DNA that is integrated into the host
genome is called a provirus
 Unlike a prophage, a provirus is a
permanent resident of the host cell
 The host’s RNA polymerase transcribes
the proviral DNA into RNA molecules
 The RNA molecules function both as
mRNA for synthesis of viral proteins and
as genomes for new viruses released from
the cell

Evolution of Viruses

Viruses do not fit our definition of living
organisms
– Since viruses can replicate only within cells,
they probably evolved after the first cells
appeared

Candidates for the source of viral
genomes are plasmids (circular DNA in
bacteria and yeasts) and transposons
(small mobile DNA segments)
– Plasmids, transposons, and viruses are all
mobile genetic elements
Where are Viruses found?
Viruses are found everywhere…
 Some have been linked to cancers,
animals, in plants
 Ex: Tobacco mosaic virus

Viral Diseases in Plants
More than 2,000 types of viral diseases
of plants are known; these have
enormous impacts on the agricultural
and horticultural industries
 Plant viruses have the same basic
structure and mode of replication as
animal viruses

Tobacco Mosaic Virus
First plant virus to be identified
 There are more than 400 viruses that
infect a variety of plants
 Virus can stunt the growth or yield a
loss in the host plants
 Plant viruses require wounds, or insect
bites to enter and infect the host

Tobacco Mosaic Virus
Vaccine

A vaccine is a harmless derivative of a
pathogen that stimulates the immune
system to mount defenses against the
harmful pathogen
– Vaccines can prevent certain viral illnesses
– Viral infections cannot be treated by
antibiotics
– Antiviral drugs can help to treat, though not
cure, viral infections
Emerging Viruses

Viruses that suddenly become apparent
are called emerging viruses
– HIV is a classic example

The West Nile virus appeared in North
America first in 1999 and has now
spread to all 48 contiguous states
Epidemic and Pandemic
In 2009 a general outbreak, or
epidemic, of a flu-like illness occurred
in Mexico and the United States; the
virus responsible was named H1N1
 H1N1 spread rapidly, causing a
pandemic, or global epidemic


Three processes contribute to the
emergence of viral diseases
– The mutation of existing viruses, which is
especially high in RNA viruses
– Dissemination of a viral disease from a
small, isolated human population, allowing
the disease to go unnoticed before it
begins to spread
– Spread of existing viruses from animal
populations; about three-quarters of new
human diseases originate this way
Some Other Well
known Viruses
Small Pox

30% of infected die
 Vaccines not
administered to
public since 1970’s
 No treatment, only
preventative vaccine
 Used as a biological
weapon
The last case of
smallpox in the
United States was
in 1949
Hepatitis

Is an inflammation of the liver
 Can be caused by 5 different
viruses
– Hepatitis A & E: can be spread by
fecal contaminated food and
water
– Hepatitis B, C, & D are spread by
sexual contact, by contact with
infected blood an serum, and by
the use of contaminated needles
– Symptoms: fever, nausea,
jaundice, and liver failure
Caused by
Hepatitis B
Influenza A, B, & C

Influenza types A or B
viruses cause
epidemics of disease
almost every winter.
 In the U.S. influenza
epidemics can cause
illness in 10% to 20% of
people average 36,000
deaths and 114,000
hospitalizations per
year
Influenza Pandemic
of 1918
http://www.youtube.com/wa
tch?v=rbYwNOcKqqc&feat
ure=channel


AIDS Virus
HIV is the virus that
causes AIDS.
AIDS is a serious
condition in which the
body's defenses
against some illnesses
are broken down.
Herpes Virus


The virus Herpes
simplex causes the
common sexually
transmitted disease
genital herpes
There are two types
of Herpes Simplex,
and both can cause
genital herpes
Most babies are born through c-section
HPV



Genital Warts:one of the
most common types of
sexually transmitted
diseases
Virus that causes them
called the human
papillomavirus
http://www.thesahara.net/
verrucas_plantar_warts.ht
m
Bubonic Plague

During the 1300s - a
massive epidemic swept
through Europe, killing
one-third of the population
by some estimates, and
subsequently changing
the course of European
history.
 Referred to as The Black
Death, Caused from
being bitten by a rodent
flea that is infected with
the disease
Polio Virus
Phase 3: Muscle
weakness
and
muscle
It enters through the
mouth & is contagious. paralysis, difficult
swallowing, nasal
Phase 1: Fever,
headache, sore throat, voice, difficulty
spewing,
breathing




malaise(general bodily
weakness and
discomfort).
Phase 2: Meningitis,
fever, severe
headaches, stiff neck
and back, muscle pain.

SARS

Originated in Asia in
2003
 Stands for Acute
Respiratory
Syndrome and can be
contracted by close
person to person
contact.
When first
introduced into the
United States,
SARS was thought
to be a chemical
weapon.
Ebola Virus
Ebola Virus, common
name for several strains
of virus, three of which
are known to cause
hemorrhagic fever in
humans, which is
characterized by massive
bleeding and destruction
of internal tissues.
Chicken Pox


Chicken pox is a rash
illness caused by a
virus.
Chicken pox usually
occurs in childhood.
More than 90% of
Chicken pox cases
occur in children less
than 12 years of
age.

Shingles
Chicken pox and shingles
are caused by the same
varicella-zoster
herpesvirus
 The virus multiplies in the
lungs and travels to blood
vessels in the skin
The painful shingles rash, caused
By a herpes virus, is limited to an
Area of the skin innervated by a
Particular nerve branch
Ex: on the side of the chest
Anthrax

Caused by the bacteria
Bacilli
Anthrax most commonly
found in wild &domestic
lower animals (cattle,
sheep, goats, camels,
antelopes
 They ingest spores from
soil
 It can occur in humans
when they are exposed to
infected animals
 Or when anthrax spores
are used as a bio-terrorist
weapon
Yellow Fever
Yellow fever is a
serious viral
infection,
transmitted by
mosquitoes in
tropical regions
 There are no
medicines that
are effective
against this virus

Emerging Viral Diseases
Are illnesses caused by new or
reappearing infectious agents that
typically exist in animal population—
often in isolated habitats—and can
infect humans who interact with these
animals.
 Ex: Ebola virus also called hemorrhagic
fever
