The Most Abundant Organism on Earth
Bacteriophages are viruses that do attack and destroy bacteria1. Just like other types of viruses, bacteriophages vary a lot in their shape and genetic material. Their genomes consist of either DNA or RNA and may contain four genes to several hundred genes2. Their genetic material is covered with a protein structure called the capsid that can be: icosahedral, filamentous or head-tail in shape2.
On earth, there are around 10³¹ bacteriophages3. But, how big is this number? Let’s do the math!
A single bacteriophage weighs around 10⁻¹⁵ gr 4. If we multiply the number of all bacteriophages with the weight of bacteriophage, we obtain the biomass of bacteriophage which equals: 10³¹ x 10⁻¹⁵ = 10¹⁶ gr. Thus, the biomass of bacteriophages exceeds the biomass of elephants. On earth, there are around 500000 elephants and the average weight of a single elephant is around 4000 kg (4 x 10³ kg) 5. So, the biomass of elephants is 5 x 10⁵ x 4 x 10³ kg = 2 x 10⁹ kg. If we convert the 10¹⁶ gr (biomass of bacteriophages) to kg we obtain a value of 10¹⁶ x 10⁻³ = 10¹³ kg. Accordingly, the biomass of bacteriophages is 10000 times larger than the biomass of elephants. (10¹³ kg > 2 x 10⁹ kg).
Imagine all the 10³¹ bacteriophages stick together in their ends in a straight line, they would stretch for 100 million light-years.
The length of a single bacteriophage varies from 24 nm -200 nm6. Let’s consider the 125 nm as an average length. The total length of 10³¹ bacteriophages would be 125 nm x 10³¹ = 1.25 x 10³³ nm.
1.25 x 10³³ nm = 1.25 x 10²⁴ m = 1.25 x 10²¹ km. But, how far is this?
1km = 1.05702341 x 10 ⁻¹³ light-years.
1.25 x 10²¹ km = ~ 1.3 x 10 ⁸ light-years7.
Distance from Earth to the moon = 4 x 10⁻⁸ light-years8.
Distance from Earth to the Sun = 16 x 10⁻⁶ light-years9.
Distance from Sun to the center of Milky Way = 2.6 x 10⁴ light-years.
The Diameter of Milky Way galaxy = 1 x 10⁵ light-years10.
Distance from Earth to the Andromeda galaxy = 2.5 x 10⁶ light-years11.
1.3 x 10⁸ light-years is bigger 100 times than 2.5 x 10⁶ light years. All things considered, bacteriophages would stretch 100 times farther than the distance from Earth to the Andromeda galaxy. It is just a virus!
3. “Novel Phage Therapy Saves Patient with Multidrug-Resistant Bacterial Infection”. UC Health – UC San Diego. Retrieved 13 May 2018
4. Endemann, H.; Model, P. (1995). “Location of filamentous phage minor coat proteins in phage and in infected cells”. Journal of Molecular Biology
8.https://www.nasa.gov/sites/default/files/files/Distance_to_the_Moon.pdf 9.https://www.space.com/17081-how-far-is-earth-from-the-sun.html 10.https://imagine.gsfc.nasa.gov/features/cosmic/milkyway_info.html