Understanding How Viruses and Bacterium Evolved and How Humans Are at RiskBiology
Five billion years ago, our planet earth was a very unfriendly place, very hot with carbon dioxide gas bubbled from molten rock and filled the atmosphere, causing such a massive greenhouse effect that the planet literally boiled dry. Living organism could not survive under those conditions. However, when water vapour to liquefy just less than four billion years ago, life was said to have appeared but was not life, as we know it now. Molecules that could replicate to produce daughter molecules with inherited characteristics, eventually microscopic single-celled organisms evolved.
These early life forms had to withstand volatile atmosphere with toxic gases, erupting volcanoes, dramatic electrical storms and the sunâ€™s ultraviolet rays all promoting uncontrolled electrochemical and photochemical reactions. The microbes resembled todayâ€™sâ€™, a type of bacteria so called because they thrive in all the particularly hostile corners of the globe.
Extremophiles inhabit acid lakes, hyper-saline salt marshes and the super heated water issuing from hot vents at the bottom of the deepest ocean trenches where they survive temperatures up to 150-250 degree C. They also lay buried deep in the polar ice caps, and lurk in rocks. It is possible that life began with microbes in rocks deep underground, where the heat is intense and there is an ample supply of water and chemicals to get the whole process started.
For around three billion years, bacteria had Earth all to themselves and they diversified to occupy every possible niche. At this stage, there was no oxygen in the atmosphere so they evolved many different ways of unlocking the energy bound up in rocks, utilizing chemical compounds of sulphur, nitrogen and iron.
Around 2-3 billion years ago, a group of innovative microbes called theÐ’Â cynobacteria (previously called blue-green algae) learnt the trick of photosynthesis, using sunlight to convert carbon dioxide and water into energy rich carbohydrates.
As a result, oxygen, a waste product of this reaction, slowly accumulated in Earthâ€™s atmosphere. At first oxygen was poisonous to early life forms, but then other ingenious bacteria discovered that it could also be used to generate energy. These new energy sources were rich enough to support more complex life forms, but the emergence of multicultural organisms had to await the evolution of eukaryotic cells.
Bacteria are â€œprokaryotesâ€, meaning that their cells are smaller than those of all higher organisms â€œeukaryotesâ€ and have a simpler structure, lacking a well-defined nucleus. However, around a billion years ago, a group of free-living photosynthetic cyanobacteria took up residence inside other primitive single-celled organisms to form the energy - generating chloroplast of the first plant cells. In addition, in a similarly extraordinary manoeuvre, oxygen-utilizing microbes called alpha proteobacteria (form of bacteria) became incorporated into other microbes as mitochondria, the power house of animal cells.
So finally, 6oo million years ago, the stage was set for the evolution of multicellular organisms made up of eukaryotic cells, and eventually the emergence of the plants and animals we know today.
However, compared to the diversity of bacteria, all other life forms, however different they may seem, are homogeneous, locked into the same biochemical cycle for energy production, and requiring sunlight for plant photosynthesis to generate the oxygen used by animals for respiration.
We still rely on bacteria (in the form of chloroplasts and mitochondria) for these reactions, and on free-living bacteria for all other chemical processes needed to maintain the stability of the planet. These bacteria recycle the elements, which are essential for life on Earth and are at the heart of our balanced ecosystems, those complex interdependent relationships that exist between plants, animals and the environment.
Although bacteria and single-celled protozoa (plasmodium) were the first to inhabit in our earth. The tiniest of all microbes, viruses, probably also evolved several million years ago. They have diversified to infect all living things including bacteria, but exactly how and when they came into being is unknown.
The genetic material of viruses consists of either DNA or RNA, but most only code few proteins and cannot survive on their own. Therefore, viruses are obligate parasites and only when they have sabotaged their hostâ€™s cells do they spring to life. Once inside they turn the cell into a factory for virus production and within hours, thousands of new viruses are ready to infect more cells or seek another host to colonize.
Perhaps because they are so small, nowadays microbes seem to be over shadowed by larger forms of life, but the are still by far the most abundant on the planet, constituting some twenty-five times the total biomass of all animal life. There are well over a million different types, mostly harmless environmental microbes. They are in the air we breathe, the water we drink and the food we eat and when we die, they set about deconstructing us. Each ton of soil contains more than 50,000,000,000,000,000 microbes, many of which are employed in breaking down organic material to generate essential nitrates for plants to utilize; every year nitrogen.-fixing bacteria recycle 140 million tons of atmospheric nitrogen back into the soil.
Bacteria are masters at survival, and when adverse conditions come along, they are generally ready. Adaptability is the key to their success, yet in theory reproducing by binary fission yields offspring that are all identical to the parent â€” a process that apparently leaves no room for variability. However, although their DNA copying machinery is accurate, mistakes occur which are corrected by a cellular proofreading system. Even so, occasional errors slip through unnoticed and these heritable changes to the genetic code (mutations) may cause changes to their offspring. This muted virus becomes a new strain that can attack human, animals or birds, similar to the new swine flu, which jumped from birds to pigs and now attacking human.
This is the basis of evolution by natural selection. In humans and other animalâ€™s evolutionary change is a slow process because of our long generation times, but for bacteria, which reproduce very fast and have a less effective DNA proofreading system, rapid change by mutation is their lifeline. A single bacterial gene mutates at a rate of one change per - cell divisions, so in a rapidly dividing colony many thousands of mutants are thrown up. A few of these mutations will confer a survival advantage and these progeny will then quickly out compete their rivals and come to dominate the population.
Bacteria have several other tricks to help them adapt- rapidly to a changing environment, mostly involving gene swapping. Many bacteria contain plasmids, circular DNA molecules that live inside the bacterial cell but are separate from the chromosome and divide independently. They supply their host bacteria with extra survival information and can pass directly from one bacterium to another during conjugation. This involves the outgrowth of a filament called a â€˜sex pilusâ€™ which acts like a temporary bridge between the donor (male) and the neighbouring recipient (female) bacterium giving plasmids free access and allowing survival genes to spread rapidly through bacterial communities. Several genes that code for antibiotic resistance, allowing bacteria to survive in the face of antibiotic treatment, are carried on plasmids, and they have succeeded in spreading worldwide.
Another way that genes can jump between bacteria is by using viruses called bacteriophages, or phages for short. All viruses are cellular parasites, and phages commandeer the bacteriaâ€™s protein making machinery to generate thousands of their own offspring, most of which carry a copy of DNA identical to the parent phage. But around one phage in a million mistakenly picks up an extra piece of DNA, either from the bacterial chromosome or from a resident plasmid, and carries it to the next bacterium it infects, If this extra piece of DNA codes for a protein that improves survival then natural selection will ensure that the offspring of the recipient bacterium will prosper at the expense of others. With their host bacteria, with the phage being safely housed inside the bacterium and the bacterium in turn being protected from infection by other more destructive phages.
Of the million or so microbes in existence, only 1,415 are known to cause disease in humans. However, despite their significance to us, these pathogenic microbes are not primarily concerned with making us ill. The devastating symptoms they produce are really just a side - effect of their life cycle being enacted inside our bodies. However, they certainly use each step of the infection process to their own advantage, and natural selection ensures the microbes that induce disease patterns that are best designed to assist their reproduction and spread survive at the expense of their more sluggish siblings.
Therefore, over time disease patterns have been sharply changed by evolution to ensure the survival of the causative microbes. A highly virulent lifestyle, killing the victim outright, is not advantageous to microbes as they will then be without a home and probably die along with their host. Yet less virulent microbes risk being rapidly conquered by the hostâ€™s immune system, and this curtails their spread. Over centuries of coexistence of microbes and their human host, evolution has fine-tuned the balance between these two extremes to optimize survival of both species, but the rapid adaptability of microbeâ€™s means that they are generally one-step ahead in the ongoing struggle.
How Humans Contributed toÐ’Â Their Destruction
Antibiotics (in the last 40 years) paved the way for doctors to develop new technologies (IVF, plastic surgery, hip replacement, minimally invasive surgery, stents, total parenteral nutrition's, transplant surgery and cardiac surgery). These technologies have made some doctors rich and famous but now the very technology is threatening our existence in this universe.
Healthcare professionals (often demanding patients) continued to treat virus infections and prescribed antibiotics often in low concentration, this practice has successfully helped us educate these bacteria to thrive on the very antibiotics that used to kill them. Introducing bacteria present on the skin into our circulation has also given these bacteria an opportunity to learn how to kill our white blood cells and destroy our immune system.
We have been advising (www.medifix.org) healthcare professionals, medical device manufacturers and pharmaceutical companies to help us reduce discarded contaminated hospital waste in the environment. They have not respected our plea nor have they made any effort to reduce introducing bacteria into our body. One site on our body in an area the size of a 2p coin was noted to be colonised with 132 million bugs, while the average count was 16 million. Introducing bacteria into our body will help these bacterias to quickly adopt, mutate and attack us. Flu & other viruses are also helping these bacteria present in the nostrils to enter our body and lungs with ease and in return, the viruses have learned to resist antiviral drugs.
I really do not know how we can bring an end to this evolutionary change, mutation of virusÐ’Â and the win the war of germs.