This slideshow presentation tells the story of the eternal battle between viruses and bacteria. Viruses cannot replicate on their own, so they would infect other organisms to hijack cellular functions in order to produce more viral offspring. While trillions of bacteria die every day due to attack of bacteriophages, the surviving ones has evolved an elegant defense mechanism that stores pathogenic sequences (from the virus DNA) into their genome, via the 'CRISPR' (clusters of regularly interspaced short palindromic repeats) region within their chromosome. The associated 'Cas' proteins paired with the RNA (expressed identifier-DNA sequences) will scan and cut out any viral DNA that matches with the stored sequences, making the virus ineffective. This makes the CRISPR/Cas system is very quick and effective tool for various bacterial detection and killing of pathogenic agents.

1. CRISPR ORIGINS:
VIRUSES vs. BACTERIA
The Eternal Battle All Around Us
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2. THE ETERNAL BATTLE
Billions of microorganisms
such as fungi, bacteria, and
viruses are constantly at war
in environments all around us.
Evolution in all its glory are as
fascinating as it is ruthless.
While essential resources and
nutrients are limited, these
micro-organisms must
compete relentlessly in order
to survive.
Source: https://thewire.in/the-sciences/how-a-battleground-between-bacteria-and-viruses-is-being-used-for-human-health

3. Difference between viruses & Bacteria
BACTERIA
Latin: “Little Sick”
• Living Single-Cell Organism
• Larger in Size (>1,000nm)
• Asexual Reproduction (via
fission), provided with enough
resources in environment
• Localized Infection: will only infect
a certain part of your body
• Can be treated with antibiotics
VIRUS
Latin: “Poison”
• Not living, no cells
• Smaller (20 – 400nm)
• Requires a host cell to invade &
take over, replicating DNA/RNA to
make more copies of themselves
• Systemic Infection: the entire
body will be affected
• Antibiotics has no effect
Source: http://www.erfejmnihe.mobi/Virus/similarity-and-difference-between-bacteria-and-viruses

4. The Bacteria
In a nutshell, bacteria are prokaryotes,
which consist of a single cell with a
simple internal structure.
The bacterial cell is surrounded by a
cell membrane (primarily made of
phospholipids). All the contents of the
cell are held within the membrane.
Unlike the more complex eukaryotes,
most bacteria have a single circular
bacterial chromosome of DNA.
Source: https://en.wikipedia.org/wiki/Bacteria

5. COMMON Bacteria TYPES
*Despite their simplicity, bacteria
can form complex associations
with other organisms.
Escherichia Coli
Staphylococcus
Lactobacillus
Salmonella
Pseudomonas
Clostridium P.

6. Source: https://en.wikipedia.org/wiki/Bacteria
Most bacteria multiply by
growing to a fixed size and then
reproduce through binary fission,
a form of asexual reproduction.
Under optimal conditions,
bacteria can grow and divide
extremely rapidly, and bacterial
populations can double as quickly
as every 9.8 minutes.
*Some bacteria have more complex
reproductive structures to disperse their
new daughter cells.
Bacterial Cell Division
Chromosome
Mother Cell
Cell Elongates
Replicates DNA
DNA Separates
Cross Membrane
Forms
Cross Membrane
Complete
Daughter Cells

7. The VIRUS
A virus is a small infectious
agent that replicates only
inside the living cells of other
organisms.
Viruses can infect all types of
life forms. Regarded as ‘non-
living’ entities, most viruses are
typically contain a core genetic
code (DNA/RNA), a protein
coat (capsid) and lipids that
surround the coat (envelope).
Source: https://en.wikipedia.org/wiki/Virus

8. COMMON VIRUS TYPES
*To date, up to 5,000
virus species have been
described in detail.
Bacteriophage
HIV
Ebola
Hep. B
Influenza
Adenovirus

9. Eternal Arch-enemies
Viruses are killing machines to
bacteria. A virus injects its DNA
into a bacteria in order to take
over control.
Since viruses cannot replicate on
their own, they infect other
organisms by ‘hijacking’ their
cellular machinery to produce
viral offspring, and kill their hosts.
Source: https://en.wikipedia.org/wiki/Virus

10. Source: YouTube Video by Kurzgezagt (https://www.youtube.com/watch?v=YI3tsmFsrOg)
The most common type of virus is
the bacteriophage. There are
more phages on earth than all
other organisms combined. They
are everywhere around us.
Phages are responsible for the
majority of deaths on earth,
trillions of bacteria every day are
killed by phages. In the oceans
alone, up to 40% of ocean
bacteria are killed by phages.
DEADLIEST BEING: THE Bacteriophage

11. THE SURVIVING Bacteria
While a lot of bacteria are killed
with every cycle of viral infections,
the surviving bacteria developed
the CRISPR/Cas system to defend
themselves.
CRISPR stands for clustered
regularly interspaced short
palindromic repeats. The viral DNA
from previous infections are
captured by ‘Cas’ proteins and
stored within the CRISPR sequence
of the bacterial chromosome.
Source: https://thewire.in/the-sciences/how-a-battleground-between-bacteria-and-viruses-is-being-used-for-human-health

12. Crispr/Cas9 DEFENSE Mechanism
CRISPR DNA is ‘expressed’ into RNA, which teams up with Cas9 as guide to recognize the
virus when it invades again. This RNA-enzyme complex finds the invading bacteriophage
DNA, binds by complementary base pairing and the nuclease enzyme cuts the viral DNA,
preventing the virus from replicating.
Source: https://www.gtac.edu.au/gene-editing-gets-crispr-in-the-news/

13. Source: https://thewire.in/the-sciences/how-a-battleground-between-bacteria-and-viruses-is-being-used-for-human-health
Each bacteria can store
multiple ‘Spacers’ acquired
from several different phages
DNA. It would then have a
unique sequence stored in its
genetic database.
If the copies match, the
bacteria proceed to destroy
the invading genetic material
by cutting it up completely.
Effective Defense

14. Source: https://www.omicsonline.org/conferences-list/major-challenges-in-drug-delivery-system
Practical Applications For Bacterial Use
Bacterial
Detection
Kill
Pathogens
Fermented
Food
Production
*Some uses of CRISPR sequences
– since they are unique, the
spacers can be used to quickly &
effectively identify the bacteria
that carry them.

15. CONCLUSION
• Viruses can't replicate on their own, so they infect other
organisms and hijack their cellular machinery to multiply their
viral offspring.
• Surviving bacteria has evolved the CRISPR/Cas, a quick and
effective defense mechanism comprising 2 parts:
• Acquisition of the virus DNA sequence by Cas proteins to store within
CRISPR;
• Interference of further viral infections by expressing the stored
sequence to couple with the Cas protein to scan and cut out the virus
DNA, rendering the pathogenic gene useless.

16. By xeraya capital
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