Bacteria and Viruses
Helpful or Harmful?
Bacteria are
99% Helpful
Viruses are
ALL harmful
VIRUS
BACTERIA
PLASMODIUM
PROTOZOA
PARASITE
VIRUS?
BACTERIA?
PARASITE?
Non-living infectious particle composed of a nucleic acid (DNA or RNA) and a protein coat
“Viruses lead kind of a borrowed life”
“A well organized molecular parasite”
1. Living or non-living?
2. VIRUS STRUCTURE
Bacteriophage,
Adenovirus
• Contains DNA or RNA
(double or single stranded)
• Viruses are specific as to
the type of tissue &/or the
species they infect
“host range”
UniqueALL
in that
it is
dependentINTRACELLULAR
on the cellular machinery
of its host…
ARE
OBLIGATE
PARASITES
SMALL
3. VIRUS TYPES
• DNA VIRUS: Use the Host By….
1. Directly produce RNA that
then makes viral proteins OR
2. Joins with host cells DNA for
direct synthesis of new viruses
• RNA VIRUS: Use the Host By….
1. Viral RNA is released into host cells cytoplasm
and uses its ribosomes to produce new viral proteins
2. “Retrovirus” -Reverse Transcriptase:
RNA + Enzyme
RNA > DNA > Integrates into the
host’s genome
*High level of mutations
Viral Life cycle 1.08
4. Replication
The simplest type of a viral replication ends
with the exit of hundreds or thousands of
viruses from the infected host cell (often
damaging or destroying it)
HIV Lifecycle 4.52
Progeny HIV* particles (red) emerging from an infected T lymphocyte (green)
showing how many progeny can be generated in a single infected cell.
(Image provided by D. Hockley/NIBSC/SPL.) *HIV = Human Immunodeficiency Virus
Text p 504
http://www.npr.org/blogs/krulwich/2011/06/01/114075029/flu-attack-how-a-virusinvades-your-body?sc=emaf
HOW A VIRUS ATTACKS YOUR BODY 3.38
Lytic Infection Stages: Attachment, Penetration, Replication, Assembly, Release
Examples…
Different
Modes of
Transmission:
Air:
Ch. Pox, MMR
Influenza
Contaminated
food or water:
Hepatitis, polio
Insects:
Y. fever, Lyme
Sexual Contact,
Blood/Needles
AIDS
…RNA vs DNA
Vaccines: Immune System
How can we fight Viruses?
Antivirals- Target Viral Enzymes
Emergent Diseases
How do viruses suddenly give rise to previously unknown/rare diseases?
An emergent
disease can
be either a
disease that
is new or a
disease that
has long
existed but
which for
some reason
has become a
new problem.
The Science of Emerging Disease
• Epidemic vs Pandemic
• How do viruses burst on the human scene?
1. Mutation of existing viruses -RNA…no proofreading
2. Dissemination from a small, isolated human population
Americas; Roads/bridges, International travel, transfusions, lifestyle
3. Spread of existing viruses from other animals.
~3/4 of human diseases
“Natural Reservoir”unaffected; transmit
H1N1(surface proteins)
SARS EPIDEMIC….HHMI
4-11 3.50-19.43
*AIDS
Viral Diseases
in Plants
• Most are RNA viruses
• Lowers Crop Yield
• Lowers Crop Quality
$15B in damage
• Horizontal: from
another species;
through damaged
cell walls
• Vertical- inherited
Viroids and Prions: subviral agents
• Viroids and Prions are simpler than viruses
• Viroids have RNA but no protein coat (‘naked
RNA’) and are the smallest known pathogens .
• Viroids cause many diseases in plants
• Prions are made of protein but have no
nucleic acid (no DNA/RNA)
• Prions cause fatal brain diseases in animals
and humans Ex- BSE- “Mad-Cow”- vCJD,
TSE’s…Creutzfeldt-Jakob disease (CJD)
*2 of 3 Domains are Bacteria
Prokaryotes
1. Living or Non-Living?
Bacteria
• Cell Wall
– peptidoglycan
• Cell Membrane
• Ribosomes
• DNA
– Nucleoid
– Plasmid
• Flagellum
– Pili
*endospores
*biofilm- p516
Text p513
Classification by shape and number
Facultative vs Obligate
•
•
•
•
•
Prokaryotic Adaptions
Shape, size, motility
Cell Wall differences
Slime layer/adhere to cells/protect against dehydration
Endospores/dormancy
Obligate vs facultative aerobes/anaerobes
Gram Positive
(stain purple)
- NOT in Archaea
- Thick cell wall made of
peptidoglycan
Gram NegativeThin peptidoglycan layer + a
thick outer membrane more
resistant to antibiotics
Nutrition
• Heterotrophs vs Autotrophs
• Chemotrophs vs Phototrophs
– Based on source of
Carbon & Energy
“decomposers” Saprotrophs”
Bacterial
Reproduction
Binary Fission
Transformation
Transduction
Conjugation
Examples
of
Bacterial
Infections
Drug Resistant Bacteria
• Antibiotic Overuse leads to drug resistant superbugs
AND loss of “Good Bacteria” How Bacteria Communicate TED 18.08
Protecting Good Bacteria
***Production of Foods and Fuels
In the home and in industry, microbes
are used in the production of
fermented foods. Yeast's are used in
the manufacture of beer and wine and
for the leavening of breads, while
lactic acid bacteria are used to make
yogurt, cheese, sour cream,
buttermilk and other fermented milk
products. Vinegars are produced by
bacteria. Other fermented foods
include soy sauce, sauerkraut, dill
pickles, olives, salami, cocoa and black
teas. Yeast are also involved in
fermentations to convert corn and
other vegetable carbohydrates into
ethanol to make beer, wine or
gasohol, but bacteria are the agents of
most other food fermentations.
Bacteria vs Viruses
Bacteria
Viruses
Can Feed, excrete, grow, reproduce
DO NOT feed, excrete, grow
INTERCELLULAR: Live between cells
Can be Autotrophs or Heterotrophs
Chemotrophs or Phototrophs
MOST are Heterotrophs: feed on dead
animals/plants/wastes or are parasitic
SOME are autotrophs- make their own food
through photosynthesis OR chemosynthesis
INTRACELLULAR- Can ONLY Live INSIDE cells
Are obligate intracellular parasites
Most viruses target a specific organ or host
cell. Binds like a “lock and key”
Makes enough ‘baby’ viruses to break out of
the cell, or the cell bursts (lytic) vs lysogenic
Bacteria vs Viruses
Treatment/Response to Antibiotics
Bacteria
RESPOND to ANTIBIOTICS
Gram Positive Bacteria- killed by penicillin.
(purple stain can get in, so can the antibiotic)
Thick Peptidoglycan cell wall
Gram Negative Bacteria (Example: E.coli) –
Stain can’t get in the cell, Antibiotic can’t get
in- resistant to most antibiotics. Outer
membrane + thin Peptidoglycan cell wall
Viruses
DO NOT respond to ANTIBIOTICS, some
slowed by antivirals
Very Hard to fight- can’t kill the virus without
harming the host cell.
Virus causes an infection- we fight THAT with
antibiotics; target viral enzymes with
antivirals.
Fight infections by hand washing, sanitation, cooking, washing food/refrigeration
VACCINES: Work on specific Bacteria or Viruses- stimulates the immune system.
Made from weakened or killed forms of the bacteria or virus. The immune system then
recognizes it and can fight it when you are infected with the stronger/live version.
The Life Cycle of Protist Plasmodium
(causative agent of malaria)
1. Infected mosquito bites
uninfected human and
transmits Plasmodium
sporozoites which enter
liver cells and divide to
produce merozoites
3. After the mosquito bites an
infected person, Gametocytes
develop into gametes in the
mosquito’s digestive tractembedding in the stomach,
producing spores that migrate to
the salivary glands, where they
are again passed to a human from
a mosquito bite.
2. In RBC’s.
merozoites
proliferate,
bursting RBC’s
and releasing
parasites to
infect new
RBC’s, some
form
gametocytes