As we know the bacterial infection that we get, is now a major threat to human life forms and the over usage of antibiotics will eventually make the bacteriae, resistant to the antibiotics consumed to stop the infection. An unanswered question is how new genes that cause antibiotic resistance arise which is very important for scientists to find out. In a new study, Swedish and American researchers have shown how new genes that produce resistance can arise from completely random DNA sequences. Antibiotic resistance results in the spread of resistant bacteria causing disease and death, which is an alarming fact these days.
What actually happens with bacteria
The most common way for bacteria to develop resistance is by taking up various types of resistance genes from other bacteria. These genes encode proteins also called peptides that can lead to resistance by either deactivating the antibiotic, or by reducing its concentration, and also by altering the antibiotic’s target so that the antibiotic can no longer bind to that target and hence halt the growth of the bacterium.
Once resistance genes develop, they can quickly spread between different pathogenic bacteria and reduce the effectiveness of our antibiotics. It is therefore critical to detect and characterize new resistance genes as quickly as possible, to monitor the spread of resistance and also to ease treatment and the development of new antibiotics.
To find out about the emergence of resistance genes, the researchers conducted laboratory experiments to investigate whether it was possible to produce a gene from random DNA sequences that would give rise to antibiotic resistance. This was done by first designing nearly one billion random DNA sequences that were then placed on a plasmid in the intestinal bacterium Escherichia coli. Plasmids are DNA molecules that replicate independently and can be transferred from one organism to another.
These random DNA sequences were then expressed in the bacterium as short peptides. While most of these peptides did not affect the bacterium at all, six different peptides did, causing the bacterium to become resistant to the antibiotic Colistin, which is an important antibiotic medication of last resort that is used in severe infections to kill the bacteria by binding to and destroying the bacterium’s cell membrane. These peptides caused resistance by increasing the expression of genes that are involved in the modification of the bacterium’s cell membrane. This modification of the cell membrane resulted in the antibiotic not being able to bind to the cell membrane, and thus not being able to reduce the survival of the bacterium.
Dan I. Andersson, who is a Professor in Medical Bacteriology and the one who is responsible for the study said, “We have now shown in two different studies that random sequences of amino acids can give rise to new functions that are beneficial to the bacterium such as antibiotic resistance. This suggests that the evolution of new functions from random DNA sequences is not as unusual as previously thought,”
“An important question that remains now and which will again require further study is whether these new genes are naturally present in bacteria or can only be observed in laboratory experiments,” says Michael Knopp, a post-doctoral researcher at the Department of Medical Biochemistry and Microbiology.