Mutation that makes Escherichia coli deadlier
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Genetic Mutation that makes Escherichia coli deadlier

Bacteria can be classified as either harmless or beneficial non-pathogenic bacteria, and harmful, pathogenic bacteria – As far as humans are concerned. We need to have an excellent grasp on the mechanisms that cause some bacteria to be virulent – To develop better therapies for disease caused by pathogenic bacteria. Researchers have discovered genes that cause virulence, or capability to cause disease, however, they do not completely understand exactly how bacteria evolve to become pathogenic.

Molecular mechanisms that cells develop to gain valuable traits were identified using a process called experimental evolution, by Professor Chikara Kaito and his team from Okayama University, Japan. Prof Kaito said, as no one has actually ever looked at virulence evolution of bacteria in animals – we’re really thrilled by this study, the researches before us looked at the cells’ evolution.

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They chose to begin with a non-pathogenic Escherichia coli and repetitively mutate it and use it to infect silkworms (an insect that is often used as a model for infectious diseases), and afterward test whether it will cause silkworms’ death.

Strains of Escherichia coli with a 500-fold increased virulence compared to the initial bacterial strain was developed by the scientists and found that one of the key factors for the virulence increase in the bacteria was due to the mutations in the gene that code for one certain protein – the “lipopolysaccharide transporter (LPS)”. This lipopolysaccharide transporter protein forms a part of the bacterial cell membrane and protects the bacteria from harm, and due to this, the LPS transporter is essential for the growth of Escherichia coil.

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In addition to some anti-bacterial substances from the silkworms, the mutations that increased bacterial deadliness appeared to give Escherichia coli resistance against some antibiotics. And the reason behind this could be an increase in the concentration of outer membrane vesicles, which the bacteria release to absorb harmful compounds to stop them from cause harm by entering the bacteria.

The features of substances that pathogenic strains were resistant to, showing that they were positively charged and hydrophobic in nature was also discovered in the study. This suits the enhanced quantity of hydrophobic and negatively charged outer membrane layer vesicles, permitting them to hold onto those substances. The study also showed that mutations occurred in parts of lipopolysaccharide transporter. This protein is present directly on the outside of the bacterial membrane layer. According to the researchers, this is because they experience more natural selection as these areas are much more exposed to the environment, and are thus more susceptible to mutation.

Prof Kaito said, what we have done here is to determine several features of pathogenic bacteria. For the first time, we revealed that mutations to LPS transporter can increase virulence, and we gave evidence for how that virulence actually happens – more outer membrane vesicles are made by the mutant bacteria. Additionally, the team also determined specific structural modifications to mutated LPS transporter that can discuss why virulence is different across bacteria – because each species might have various structures.

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Prof Kaito said (When asked about exactly how his work contributes to scientific understanding and medicines), it had not been really clear before our research study – how bacteria actually evolved properties that made them more harmful, so our research aids in making this clear. The outcomes of the study indicate the possibility of creating drugs or various other therapy that can keep bacteria from becoming pathogenic, specifically if we find more proteins like LPS transporter, where such a huge impact can be caused by mutations.

More researches and studies are certainly needed to explore whether the mutations observed in this study will certainly increase virulence when the bacteria infect mammals. However, this research is absolutely the first step towards untangling the secret of differences between bacteria that is dangerous and beneficial.

The outcomes of the study based on ‘Mutation that makes Escherichia coli deadlier’ were published in PLoS Pathogens.


Author: Sruthi S