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How Bacteriophages Kill Bacteria. Procedure

How Bacteriophages Kill Bacteria?

How phages kill bacteria is very simple. It is similar to the principle that viruses kill other cells. As long as you have a junior high school biological knowledge, you should understand them, and there is no need to repeat it here.

I want to talk about the mechanism by which bacteria may resist phage killing. This is also an important reason why some people worry that phage therapy may still be tolerated by bacteria.

When it comes to bacteria being resistant to phages, this is indeed possible. This has to talk about CRISPR.

CRISPRs are Clustered Regularly Interspaced Short Palindromic Repeats (ie, clustered, regularly spaced short palindromic repeats). The discovery of this genetic structure is quite accidental:

In the 1980s, when researchers studied the E. coli genome, they found that there were some strange repeats at the end of one of the bacterial genes, and there were special spacers between the repeats. As for the role of these strange sequences, it was not known at the time, so they were named using CRISPRs.

In the 1990s, when researchers compared genes of some different species, they were surprised to find that CRISPRs sequences do not exist in all kinds of bacteria, and CRISPRs sequences are exactly the same as some gene sequences of several phages! At that time, some people put forward the hypothesis that this may be the opponent characteristic sequence left in the battle method of bacteria and phage for more than a billion years, thereby guiding the bacteria to hydrolyze the phage genome and thus kill the phage.

Imagine it is similar to an unlucky egg attacked by a face bug.

 Phage Killing bacteria

The face bug implanted a heteromorphic embryo into him, but this unlucky egg has a face bug / speciality recognition system. When the embryo is found, it is killed. In the end, the unlucky egg survived, and the face bug / alien was cool.

This theory was verified experimentally in 2005. And it officially revealed the working principle of CRISPR: bacterial cells can use genes related to CRISPR repeats to produce some special proteins, namely CRISPR-related proteins, which are translated into English as CRISPR associated proteins. Take the first letter, that is, Cas. protein. When the virus invades the bacterial cells, these Cas proteins bind to the viral DNA and "cut" the next piece from above. This piece of viral DNA is then transported into the genome of a bacterial cell, inserted into it, and becomes a "spacer." From then on, bacterial cells will use this gap to identify the virus that corresponds to it, thus fighting the virus more effectively.

So Cas protein is the magic weapon that bacteria use to fight phage. And unlike the immune system of vertebrates, the diseases immuned by parents can't be passed on to the next generation; the immune system of bacteria can be inherited.. I don’t know where it is higher than our self-seeking primates It's up!!!!
How Phages Kill Bacteria, the Procedure

CRISPR-Cas system Efficient and Convenient Gene Manipulation Tool

Later, the CRISPR-Cas system was developed by scientists to become a more efficient and convenient gene manipulation tool, thereby playing a greater role in the field of genetic modification.
When the earth only had single-celled organisms, and even archaea, phages were obviously their natural enemies. Thanks to the presence of phages, the number and scale of archaea were controlled, thereby ensuring that the first batch of life on the earth would not be caused by ecology, crisis. But at that time, after all, bacteria could be packed, except for natural disasters, which are phages. 

Current research has found that as many as 90% of archaeal bacteria have a CRISPR-Cas system, showing how cruel the fight between bacteria and phages at the time.

Once the phage has a base mismatch during the replication of genetic material, the bacteria's original CRISPR system may not be able to recognize it. This is where the phage is "magic".
Therefore, even if a certain pathogenic bacteria produces a corresponding anti-phage CRISPR in the future, the mutation of the phage can still kill it.

In addition, biological resistance and characteristics have a price. Bacteria can synthesize antibiotic-resistant proteins, and there is no more raw material to synthesize Cas protein, so the possibility of both resistances is very low. In addition, the phage itself is also mutating, which gives humans a chance in this war against bacteria.

Author's Bio

Doctor Shawna Reason, Virologist
Dr. Shawna Reason
Name: Shawna Reason

Education: MBBS, MD

Occupation: Medical Doctor / Virologist 

Specialization: Medical Science, Micro Biology / Virology, Natural Treatment

Experience: 15 Years as a Medical Practitioner

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