Long-Term Friends

2

December 2016
Ivan Obolensky

If you feel sick with cold-like symptoms, the question asked most often is, do I have a viral or bacterial infection? If it is a viral infection, you know you’re out of luck in terms of antibiotics, and unless the illness is caught early, there is nothing to be done other than persevere and hope that you get better soon. The usual medical advice is to get lots of rest and drink plenty of liquids.1

You might ask, why is it so hard to treat viral infections? They seem to be worse than bacterial infections. Perhaps it would be best if we rid the world of viruses altogether.

Perhaps not.

Viruses are ten times more numerous than bacteria with over 100 million different types. They are the most numerous life form on earth, more than all others combined. Most viruses act to control the bacteria population, which left unchecked would cover the planet in a gooey sludge. Marine viruses kill 20 to 40% of all ocean bacteria each day, allowing more complex aquatic life, and ultimately ourselves, to exist.

Viruses need bacteria to survive, but bacteria also need viruses. Viruses help to spread the genetic material of bacteria throughout the host population, letting bacteria rapidly adapt to environmental changes.2

Viruses and bacteria have been battling and helping each other for billions of years.

Although the most obvious difference between the two is that viruses are much smaller and less complex, both evolved from earlier cellular life and ultimately have the same self-replicating ancestor. They are related, yet very different. How is that possible?

Imagine Nature coming to a crossroads with a choice of two paths. One is marked by a sign in the shape of an arrow that reads complexity. The other is marked with a similar arrow, but this one spells out simplicity. Which path would you choose? Nature decided to take both.

The split occurred around 3.4 billion years ago. While bacteria took the complex pathway to larger multi-cellular structures, viruses jettisoned everything except the absolutely necessary and grew smaller. A typical influenza virus is just fourteen protein genes surrounded by a protein sheath.3

What made this diversification possible? Water.

Water is the medium in which viruses and bacteria can interact. It is also the reason that humans, bacteria, and viruses have had such a long and complex relationship.

Humans are basically water creatures and must have large quantities of water to survive, more than most mammals. Under extreme conditions, a human body can release three gallons of sweat in a single day. Most civilizations took root around rivers and other water sources for this reason. Even today, access to potable water acts as the primary prerequisite to human survival rather than food.

Heat regulation is important for all warm-blooded creatures. The skin of mammals functions as a radiator. Networks of small blood vessels carry heat from inside the body and radiate that heat outward.  Humans utilize this mechanism as well, but the human cooling system is more effective.

Humans have two types of sweat glands: the eccrine and apocrine. We excrete two forms of sweat.

The eccrine glands secrete a clear odorless liquid to promote heat loss through evaporation. The highest density of sweat glands is found on the palms and soles of the feet, although humans sweat from all parts of the body. In most other mammals, eccrine glands are only found on hairless areas such as foot pads and snouts.

Our apocrine glands are located on specific areas of the body. The armpit is one. They do not respond to thermal stimuli, but emotional stimuli. The smell associated is not from sweat, which is odorless, but from bacterial decomposition. Other non-primate mammals have apocrine glands over most of their bodies, but not eccrine glands.

The large number of eccrine glands, and the ability to rapidly cool the body, allowed humans to develop persistence hunting. Continually chasing herd animals led to the prey’s overheating and eventual collapse. No claws or large teeth were needed. The ability to run down prey coupled with extraordinary sensing ability made humans one of the planet’s most dangerous of predators.

As a side note, human sensing abilities have often been underrated when compared to other animals; Kalahari bushmen are said to be able to see four of Jupiter’s moons with the naked eye.

Either due to changes in climate or overhunting, available prey grew scarce, and mankind developed agriculture. With the ability to stockpile food, life changed markedly, and humans no longer needed to live in small groups to prevent overtaxing the environment. Food became abundant, and population sizes increased. Water was still a vital component because plants needed water as well, and often in large amounts. Cities sprang up and with their large and densely packed populations, bacteria, viruses, and humans developed a more intimate relationship. The abundance of water, population size, and increased population density allowed infections by both viruses and bacteria to become self-sustaining in their human hosts.

In contrast, our hunter/gatherer ancestors lived in smaller groups of fifty or less that allowed early man to experience fewer of the infectious diseases we know today. 4

At some point viruses reached a similar juncture to that reached 3.4 billion years ago, when single-celled life split into viruses and bacteria. Viruses could have either evolved towards still greater simplicity or taken a turn towards complexity. Once again Nature’s answer was both. Giant viruses containing more than 1,000 genes have been discovered that are almost the size of some bacteria.

Along the pathway towards greater simplicity, how much simpler could a virus become? Although there is no connection that has been discovered, it is possible that prions are the most stripped-down viruses of all. Prions are proteins* with a unique shape that act as infectious agents, inducing other well-formed proteins found in the nervous systems of mammals to misfold, which kills the nerve cell and leads to various brain diseases.5

The way proteins are folded can result in disease, but protein folds are also an important investigative tool. Deciphering the evolutionary track of bacteria and viruses is difficult because the soft protein shells of viruses do not fossilize, nor do most bacteria, meaning there is no historical record. Mapping the shapes of viral proteins and comparing them to those of other microorganisms, such as blue green algae which do fossilize, makes it possible to sketch out a history.

Today the relationship between viruses, bacteria, and humans is even more interconnected, as genome research has discovered in several recent advances.

One is that certain bacteria species have been found to have developed immune systems against viruses, which ultimately might prove significant.

Complex organisms are made up of cells with a nucleus in which strings of nucleotides** form strands of DNA that act as genetic blueprints. Specific sequences of nucleotides within those strands program the manufacture of the molecules that cells need to sustain themselves and to replicate.

A single-celled organism is like a small factory that produces proteins as well as other molecules the cell needs and then recycles them. Viruses inject their own DNA into a bacterium and take over its internal manufacturing structures, eventually killing the bacteria and releasing many more viruses.

Staphylococcus bacteria, that produce strep throat in humans, contain peculiar DNA sequences that repeat like a palindrome. (A palindrome is a word that spells the same backwards or forwards, like the word MOM.) These sequences became known as Clustered Regularly Interspersed Short Palindromic Repeats, better known as CRISPRs. Between the repeats are spacers that contain copies of the DNA sequences of viruses that preyed on the strep bacteria.

The repeats, spacers, as well as protein-splitting enzymes*** called CRISPR associated enzymes (Cas enzymes), form one of strep bacteria’s defenses. CRISPR encodes the necessary information to identify unwanted virus DNA and destroys it.

Where research in this area took a unique turn was in recognizing that any DNA sequence up to about 20 nucleotides long could be programmed for removal using the CRISPR system, or replaced by a different sequence in a much more precise way than previous techniques were able to do.

The implications for gene editing are impressive.

Although the use of the CRISPR system is not 100% effective, it opens the door to the not-too-distant possibility of replacing harmful genes, preventing genetic deterioration, as well as taking out specific diseases. 6, 7 , 8,  9

On the other hand, utilizing viruses that attack specific bacteria may also prove to be a means to either augment currently available antibiotics or replace those that are no longer effective.

There is still a long way to go before you can go into a doctor’s office and smile when you are told you have a viral infection. Just the same, it is no longer an impossibility and when you are able to, humans, viruses and bacteria will have entered into a whole new relationship where each can be of service to the other.


 

*Protein: large molecules that form into strands (similar to a hair, which is a protein) made from blocks of amino acids (amino acids contain amino groups, NH2. The name is similar to ammonia because the two are similar only ammonia is NH3).

** Nucleotide: a molecule that when linked together forms DNA (deoxyribonucleic acid) that is the famous double helix that forms our chromosomes or genes.

***Enzymes: a substance in living organisms that promotes a chemical change (splitting a protein, for instance) without itself undergoing a change.


 

  1. Although this can be found as advice at various websites (See: http://www.hcfwcda.com/Health-Care-For-Women/pdf/commonconcerns.pdf), it has been pointed out that it has never been clinically proven. (See: http://www.nytimes.com/2011/01/11/health/11really.html.) That being said, where this advice probably started was during the Spanish Influenza of 1918. Many victims stopped resting too soon, only to succumb from secondary infections or a return of the symptoms. In many cases, victims of the pandemic took many months to recover. (See: The Great Influenza: The Epic Story of the Deadliest Plague in History by John M. Barry).
  2. Crawford, D. (2011) Viruses: A Very Short Introduction. New York, NY: Oxford University Press.
  3. Richter, V. (2015) What came first, cells or viruses? Cosmos. Retrieved December 4, 2016 from https://cosmosmagazine.com/biology/what-came-first-cells-or-viruses.
  4. Desowitz, R. S. (2015) New Guinea Tapeworms and Jewish Grandmothers, Tales of Parasites and People. New York, NY: W. W. Norton & Company.
  5. A. (2013) What are Prions? The Prion Alliance. Retrieved December 4, 2016 from http://www.prionalliance.org/2013/11/26/what-are-prions/.
  6. Zhang, S. (2015) Everything You Need to Know about CRISPR, the New Tool that EDITS DNA. Retrieved December 4, 2016 from http://gizmodo.com/everything-you-need-to-know-about-crispr-the-new-tool-1702114381.
  7. Zimmer, C. (2015) Breakthrough DNA Editor Born of Bacteria. Quanta Magazine. Retrieved December 4, 2016 from https://www.quantamagazine.org/20150206-crispr-dna-editor-bacteria/.
  8. A. (2012) CRISPR Systems in prokaryotic immunity. The Doudna Lab. Retrieved December 4, 2016 from http://rna.berkeley.edu/crispr.html.
  9. Gervelis, H. (2013) The CRISPR Immune System in Bacteria and Archaea. Retrieved December 4, 2016 from https://microbewiki.kenyon.edu/index.php/The_CRISPR_Immune_System_in_Bacteria_and_Archaea.

 


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© 2016 Ivan Obolensky. All rights reserved. No part of this publication can be reproduced without the written permission from the author.

  1. Craig Houchin
    Craig Houchin12-08-2016

    Hey Ivan,

    Thanks for the article. Your science writing is always informative and enjoyable. It’s like going to school without the bullying and bad lunches.

  2. SILVIA
    SILVIA12-09-2016

    Hello Ivan and thank you.
    I had no idea of the relationship between virus and bacteria, fascinating.

    This article reminded me a comment a Doctor made about 5 years ago: the viruses are becoming more resistant to medicines/antibiotics and, he added, Doctor are concerned on how their evolution is going to affect the medical field in finding new ways to combat them.

    Thank you for sharing your knowledge.

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