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Health and Fitness Science

Bacteriophage: How A Forgotten Virus Can be An Asset to Combat Superbugs

What is the first word come to your mind after hearing the word ‘Virus’?

Disease, infection, infectious, harmful, etc. right.

What if tell you there are viruses that can cure our diseases.

Haven’t heard before! But there does exist such viruses, which are friendly to humans.

Just like there are god bacterias, there are good viruses.

These bacterias are known as ‘Bacteriophages’ or ‘Phages’meaning bacteria eaters.

These are good because ‘Bacteriophages’ are extreme enemies of deadly bacterias which has the potential to kill us. Believe it or not but phages are the most deadly beings on the planet.

Phages were discovered independently by two researchers Frederick William Twort at the University of London in 1915, and Félix d’Herelle who confirmed the finding and coined the term bacteriophage in 1917.

Below are some mind boggling facts about phages-

  • They are the most abundant microorganism on the planet. Much more in number than the total number of bacterias present. To give you an idea. They are everywhere, in soil, in water, in your body. Just your bare hand contains more than 10 billion phages. That’s a huge number right. The pie chart below depicts the number of phages compared to rest of the microorganism
Abundance of phages
  • Phages are 100 times smaller than bacterias. Under a normal microscope, they are not visible. You need an electrone microscope to see them.
  • The human gut contains almost one million billion phages. Whereas just one ml seawater contains one billion phages.

The most fascinating thing is that phages do not affect humans but only bacterias. Unlike other viruses phages can be a great weapon for us to fight with deadly bacterias.

How does a phage look like?

Bacteriophage Structure
Bacteriophage Structure

This is how a typical phage looks like. A head, a neck and a tail depicted in the above structure. Their genetic material is contained in a prism shaped head, surrounded by a protein capsid.

Like any other virus phages need a host cell in order to reproduce and become alive. When alone they are equivalent as dead.

Image of a phage under electron microscope
Image of a phage under electron microscope

How do phages kill deadly bacterias?

Phages are very specific in killing bacterias. What I mean is a particular type of phages can only kill a specific set of bacterias not all types of bacteria.

In order to kill a bacteria, phages first bind to the bind to specific receptors on the bacterial cell surface with their tail fibers and create a hole, a process which, along with attachment, is coordinated by the base plate.

Next,  a rigid tube is propelled out of the sheath, puncturing a hole in the bacterial cell membrane through which they inject their genetic material (DNA or RNA, double or single stranded).

From here, there are two ways via which phages can kill the host cell. One is known as lytic cycle, where after injecting (DNA or RNA) into the host cell, the phage genome synthesizes early proteins that break down the host DNA, allowing the phage to take control of the cellular machinery.

The phage then uses the host cell to synthesize the remaining proteins required to build new phages. During this process, the host cells gradually become weakened by phage enzymes (known as endolysin) and eventually burst. The whole process looks like the image below-

Different stages of lytic cycle
Different stages of lytic cycle

In another way, known as lysogenic cycle allows a phage to reproduce without killing its host. Following the injection of the phage DNA into the host cell, it integrates itself into the host genome, with the help of phage-encoded integrases, where it is then termed a prophage. The prophage genome is then replicated passively along with the host genome as the host cell divides. Something like shown in the below picture-

Different stages of lysogenic cycle

This process does not kill the bacteria directly but then under the right conditions (UV light, low nutrient conditions), the prophage can become active and come back out of the bacterial chromosome, triggering the remaining steps of the lytic cycle and kill the bacteria.

How does a phage decide whether to enter the lytic or lysogenic cycle when it infects a bacterium host cell?

One of the major factors is the number of phages infecting the host cell at once. Larger numbers of co-infecting phages make it more likely that the phages will use the lysogenic cycle.

This strategy may help prevent the phages from wiping out their bacterial hosts by toning down the attack if the phage-to-host ratio gets too high.

Because phages need a host cell to reproduce, they don’t want to run out of hosts. Thus, the tendency to flip to lysogeny at high abundance might have been favored by natural selection (explaining why phages are in such huge numbers).

But why are we suddenly interested in bacteriophages?

Although discovered first in 1917, we never paid enough attention to phages and there is a reason behind that.

In the earlier days, just a single cut in your body could have killed you. Bacterias were the culprits. We didn’t have any answer for them. People then moved their attention towards phages and successfully cured bacterial diseases by applying phages as weapons.

However, in 1928 Sir Alexander Fleming discovered penicillin and everything changed. We invented antibiotics and they were so effective against bacterias that we forgot about phages.

We became so habituated with antibiotics that we used them more and more for less and less serious causes. We lost respect for the little monsters (bacterias) and the weapon (antibiotics).

As a result, with time bacterias started to become immune against our invented weapon (antibiotics). Today there are hundreds of bacterias which are resistant towards most of our antibiotic. They are known as ‘multi drug resistant bacteria’.

Once we feared that soon there might be some bacterias that will be resistant to all our invented antibiotics and we will again go back in time, where a simple cut can kill us. Sir Alexander Fleming warned us-

there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant.

We have already created such monsters known as ‘Superbugs‘. And believe it or not but they can wipe out human existence.

In fact, according to a survey, by 2050 superbugs could kill more humans a year than cancer. The days when a cut or cough or simple infection could kill you or your loved ones are coming back.

In such circumstances, scientists again turned their attention to forgotten tiny phages. In fact, phages are perhaps better than antibiotics to combat with bacterias.

Because antibiotics are like unguided missiles. It kills everything (good and bad bacteria) that comes within its range. But phages are very specific, they are like guided missiles.

By now, you already know how phages kill bacterias (discussed above).

In fact, there are many instances recently, where doctors have used phages to treat patients successfully.

You might be thinking, won’t bacterias develop ways of defending themselves?

They will evolve against phages too. But wait a minute, phages are also microorganisms, so they evolve too. There is a constant war going on between phages and bacterias from billions of years. Fortunately, phages won the battle almost all the time.

And even if bacterias become immune against phages someday, we will still be able to win against bacterias. It has been found that in order to become resistant to even just a few species of phages, bacteria have to give up their resistance to antibiotics. It’s like attacking the enemy with two different classes of weapons.

This has already been successfully tested patients who had no other hope left. Bacteria have no answer to the combination of phages and antibiotics.

But why don’t we hear more about phages in medical science?

Unfortunately, although there is a growing interest among scientists about phages but treatment via phages is still in an experimental state. Pharma companies are reluctant to invest in phages to a great extent. As a result, it has not become part of medical treatment. There is no official approval yet.

But things are changing, in recent years phages are getting more and more attention. Research is going on to see how safe phages are if we inject them from outside.

We better do more sound research on phages and make them a part of our medical treatment before superbug kills millions of lives all over the globe.

It might sound weird but injecting the deadliest being on the planet into the human body might save millions of lives. And who knows one day your doctor might write you a prescription for phages along with or instead of antibiotics.

An informative video on this topic-

Please, never use antibiotics mindlessly. Do remember what Sir Alexander Fleming said-

Sir Alexander Fleming On Antibiotic Resistence

Source:

  1. Technology networks
  2. Khan Academy-bacteriophage
  3. Phage treatment of human infections
  4. Encyclopedia Britannica
  5. Advantages and Limitations of Bacteriophage

Categories
Health and Fitness Personal Growth Science

Trehalose: A Wonder Sugar or a Double-edged Sword

From where do we get the energy to run, walk and doing other stuff?

The answer is obvious! From the food we eat, right.

Ok, but what if I tell you to dig little deeper. Let’s recall some mechanism of our body to generate energy.

You eat some food. Our body then digests that food with the help of acid and enzymes. When the body digests the food, carbohydrates in the food (starch and sugar) breaks down into another type of sugar called glucose. When small intestine in the body absorbs glucose, it leads to the formation of a special molecule called Adenosine triphosphate (ATP). This ATP is used as a currency of energy in the body. Individual cells in the body transform this ATP to ADP (Adenosine triphosphate) and release energy required for bodily functions.

Have you observed whenever you eat some table sugar you get a burst of energy? Why is that?

Table sugar contains Sucrose a disaccharide or a molecule consisting of one glucose and one fructose molecule. In the body Sucrose (table sugar) breaks down into glucose (and fructose) and because of this molecule, you feel that burst of energy.

Have you seen some insects when they fly, how quickly their wings move (that needs a huge amount of energy)? So, is glucose the reason for their energy too?

Yes, but that glucose they don’t get from sucrose but from another disaccharide called trehalose. Unlike sucrose, trehalose is made up of two glucose molecule. This trehalose in insects is responsible for giving them rapid energy. This is due to the fact that one trehalose molecule produces two glucose molecule upon breakage of the glycosidic bond ( the C-O-C bond in between as in the picture below). Whereas sucrose or even starch produces only one glucose upon breakage of one glycosidic bond.

Is trehalose any special compared to sucrose?

Yes in many ways. Creatures which contains trehalose can survive in extreme cold conditions and even without water they can survive. Trehalose prevents protein aggregation which normally happens in extremely dry conditions.

Ever imagined how plants grow in deserts, where no water is there?

It’s because those plants contain trehalose and they may crack and dry out but revive again during rain due to the function of trehalose (which I will discuss later).

There has been a great amount of research done and going on about the wonder functions of trehalose and how human beings can benefit from them.

Trehalose is present in a wide variety of organisms including bacteria, fungi, insects, invertebrates and in some plants. However, humans do not contain this sugar in their body. We don’t have enzymes to produce this. The interesting thing is, we have enzymes to break trehalose (called trehalase) but not to build it.

How do we get trehalose for commercial use?

Extracting trehalose was once a difficult and very costly process. That’s why it wasn’t commercialized until the year 2000 when a Japanese (Okayama) company discovered an efficient cost-effective process to extract trehalose from starch. After that the cost of trehalose fall dramatically. Today it is available in the market at a very cheap price.

How does trehalose help to survive in extremely dry conditions?

The success of trehalose compared to structurally similar sugar can be attributed to it’s high chemical stability and high hydrophilicity.

High chemical stability because of 1,1′-glycosidic bond in trehalose makes it a non-reducing sugar, which gives it resistant towards hydrolysis in acidic conditions. It’s melting point is around 203 degrees. Its stability over a wide range of temperature and pH gives it an advantage over other sugars.

High hydrophilicity because water molecules are trapped in it due to its unique structure. In another way, the structure of trehalose disrupts the tetrahedral structure of hydrogen bonds. It gets in between the hydrogen bonds of water. Due to this disruption, water molecules cannot show it’s normal properties like crystallizing at a lower temperature. That is why trehalose is so important in organisms to survive in extreme cold weathers.

Moreover, it can stabilize DNA, stops aggregation of proteins and stabilizes membrane functions. Water is indispensable to life and trehalose helps organisms to survive in difficult conditions by manipulating normal properties of water.

How can we utilize trehalose to get maximum benefits?

Because of it’s higher thermostability and poor reactivity towards amino compounds it can mask unpleasant taste and odor of foods. Therefore, it is widely used as a preservative to maintain the quality of foods. US Food and Drug Administration recognized it as safe for humans in 2000.

Trehalose also has a suppressive effect on the oxidation of fatty acids. Oxidation of fatty acids in the body generates unsaturated aldehydes which are responsible for an unpleasant body odor, especially in older people. No wonder trehalose is a hit product in the cosmetic market.

Due to it’s ability to keep water under control, it is used as an eyedropper to treat dry eyes. Although the human body cannot generate trehalose, we have enzyme trehalase present which can break trehalose into two glucose molecule (which indicates that our body had been exposed to trehalose long back).

One of the most engrossing research studies is whether trehalose can protect human tissues from extreme weather and other oxidative stress as they do in case of lower organisms?

Some in vivo studies shows positive results in that way. However, a lot to be done in that direction.

Before we get too excited, a very recent research paper warned us about the exposure of trehalose to the human body.

C. diff (Clostridium difficile) is a deadly bacterium for humans. In recent years, UK, Europe, USA have seen an outbreak of C. diff bacterium at hospitals. The study shows that this deadly bacterium has a unique mechanism to breakdown the low concentration of trehalose and thus flourish in the body. Now trehalose is very commonly used in cake, pastry, fruit juices, chocolates due to its low calorific value. It’s no wonder if trehalose is giving the bacteria a growing environment, it will soon become a superbug (Know here about Superbug).

So what’s the conclusion about trehalose?

First of all, more research is required to know some more insights. Trehalose can be a weapon to humankind in the future. It can make us more robust and we may able to survive at the extreme conditions of nature we can’t imagine now. We may be able to eliminate a lot of deadly diseases utilizing it. To achieve that along with research we need awareness among people. It has a lot of potentials to become a boon to humankind but at the same time, we have to know the limitations.

Why awareness you are thinking?

Because who knows the sweetener in your favorite ice cream might lead to the growth of a superbug in your body.

Remember the quote by Paulo Coelho.

Have a cognizant week. Until next time. -Joy

Source:

  1. Extraction of Trehalose
  2. Pure Appl. Chem. trehalose
  3. Caution about trehalose, recent Nature Paper
  4. Trehalose: a multifunctional molecule