Horizontal Gene Transfer and Antibiotic Resistance: A New Threat?
The world is facing a new threat to human health. It’s called horizontal gene transfer (HGT) and it involves the movement of genes from one organism to another. HGT occurs when an organism acquires a foreign DNA sequence through some sort of physical or chemical means. For example, a bacterium might ingest a virus that contains a genetic material that allows it to survive. Or, a fungus may acquire a bacterial genome by consuming the cell wall of another organism. Although HGT has been well-documented in plants and fungi, there was a belief in the scientific community that it was not a threat to human health. This is because HGT occurs mainly at the genetic level and its effects are usually limited to physical traits, such as color, smell, or growth patterns. However, the recent development of a new class of antibiotics that has completely wiped out several types of drug-resistant bacteria has researchers worried that HGT may be more than just a theory.
HGT is indeed a threat to human health. Each year, thousands of people die each year as a result of antibiotic resistant bacteria. This toll continues to rise each year.
Although the medical community has made many strides in this area, these have been mostly limited to the treatment of infected patients. In terms of prevention, there has been little success. One of the reasons for this is that it is hard to keep up with the rate that these deadly disease mutate. However, with the implementation of HGT, this could change. If a new class of drug-resistant disease could be created through HGT, it would be nearly impossible to stop. It is for this reason that the medical community needs to do everything within its power to prevent HGT from becoming a reality.
Genes are the building blocks of all living organisms. They control everything from the production of proteins, which carry out most of the functions in the body to determining eye color. The human body has approximately 25,000 genes.
They are divided into groups called chromosomes. Each chromosome consists of two identical strands that spiral around each other. The strands are made up of chemicals called base pairs. There are only four different base pairs (C, G, A, and T) which are the building blocks of DNA. Every chromosome has a “start” and “stop” base pair. This is important because it determines when a gene is turned on and off. If a chromosome does not have a “start” base pair, the gene is never turned on. On the other hand, if it does not have a “stop” base pair, then that gene is never turned off. This is how traits like red hair or blue eyes can be dominant in certain individuals.
Most of the time, genes are transferred from one generation to the next through a process called vertical gene transfer. During this process, special enzymes go into each cell and extract the DNA of each chromosome. Afterward, a cell divides, and the chromosomes split up between the two cells.
Then, each chromosome divides into two strands and the base pairs bind together to form a molecule of DNA. This is when the cell undergoes vertical gene transfer. This process occurs when a parent passes on traits to their offspring.
However, in recent years, scientists have found a second way that genes are transferred. This process is called horizontal gene transfer. During this process, a cell does not divide, the chromosome does not split up and the base pairs do not bind together to form a molecule of DNA.
Instead, naked bits of DNA float freely in the cytoplasm of the cell. A free-floating piece of DNA can then bind with a strand of RNA and convert it into DNA. The cell can then use the instructions in the RNA to create a protein. These proteins can do just about anything, from digesting food to fighting off diseases.
The main reason why this process is important is because it allows disease-causing bacteria to transfer genes that allow them to resist antibiotics. Thanks to this process, antibiotic resistance has become a major problem in medicine. Fortunately, this process isn’t perfect and not every bacterium is going to pick up a new trait.
It seems to only occur in a small portion of the population. It also takes time for these changes to occur. That’s why, as new types of antibiotics are produced, the amount of time before they become useless is extended. It is likely that the use of antibiotics in medicine, agriculture and industry will continue to speed up the process of horizontal gene transfer. If this trend continues, doctors may soon reach a point where they have to resort to treatments that our ancestors used centuries ago.
Fortunately, the fourth outbreak of the plague is on a distant island in the Pacific Ocean. Thanks to quarantine measures, the disease doesn’t spread to the rest of the world. The U.S.
military quarantines the island nation and helps to provide supplies to the survivors. The U.S. also helps with the mass burials of the dead, which number in the millions. Quarantine measures are stepped up at ports around the world. In the coming months, it is announced that there will be stricter measures at airports.
To prevent the spread of the disease, some people choose to live in voluntary quarantine. For instance, teachers at schools and colleges go on strike. Instead of teaching, they collectively choose to sit at home until the plague is over.
Stores are shut down and there is a stoppage of mass transit. The military tries to maintain some level of normalcy, but basic supplies are in shortage. The military hierarchy still keeps the rank and file in line, but mental breakdowns begin occurring.
As the plague rages on, people begin to go insane or die. You have to wonder if the human race will survive this plague.
Will humanity survive the fourth outbreak of the plague?
Sources & references used in this article:
- Survival of antibiotic resistant bacteria and horizontal gene transfer control antibiotic resistance gene content in anaerobic digesters (JH Miller, JT Novak, WR Knocke, A Pruden – Frontiers in microbiology, 2016 – frontiersin.org)
- Dissemination of antimicrobial resistance in microbial ecosystems through horizontal gene transfer (CJH Von Wintersdorff, J Penders… – Frontiers in …, 2016 – frontiersin.org)
- Horizontal gene transfer and the genomics of enterococcal antibiotic resistance (KL Palmer, VN Kos, MS Gilmore – Current opinion in microbiology, 2010 – Elsevier)
- Horizontal gene transfer in the human gastrointestinal tract: potential spread of antibiotic resistance genes (JR Huddleston – Infection and drug resistance, 2014 – ncbi.nlm.nih.gov)
- Transfer of antibiotic resistance genes between gram-positive and gram-negative bacteria. (P Courvalin – Antimicrobial agents and chemotherapy, 1994 – ncbi.nlm.nih.gov)
- Transfer of antibiotic-resistance genes via phage-related mobile elements (M Brown-Jaque, W Calero-Cáceres, M Muniesa – Plasmid, 2015 – Elsevier)