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About 15-20 million years ago, something called the Big Bang phenomenon happened. Starting from there, another big phenomenon occurred millions of years after; the most primitive proof of life emerged in the form of small organisms called bacterium.

But what is it that defines living organisms?

For starters, its chemical complexity and cellular organization; second thing is their (our) capacity of extract, transform and use energy; and by last, but not the less, the replication capacity.

If we compare a bacterium and a virus the main difference is the capability of bacteria of living outside the body, while a virus is an obligate intracellular parasite. This resides in the lack on enzymes for energy production as well as its ’lack of replication components within the structure of the virus.

Many scientists think of this as a replicator paradigm (do not confuse with replication paradigm or replication crisis), as the entire history of life is a story of parasite-host coevolution (Koonin & Starokadomskyy, 2016). Whether viruses are alive or not they play, in fact, an important role within the biological world and life itself.

References:

Koonin, E. & Starokadomskyy, P. (2016). Are viruses alive? The replicator paradigm sheds decisive light on an old but misguided question. Studies in History and Philosophy of Biological and Biomedical Sciences 99, 125 – 134

Lehninger. Principios de Bioquímica. 3a ed. Nelson D. y Cox, M. Editorial Omega (2002). 1 vol.

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It was inn 1979 when Francis Crick came with the idea of controlling the cells within the brain while leaving others unaltered. He later speculated that light might be useful as a controlling tool.

Optogenetics, by meaning, is the combination of genetic and optical methods to gain or loss a function in specific cells (Disseroth, 2010). The system is based on the expression of light-sensitive receptors (opsin proteins), and the controlled delivery of light. The opsins are usually delivered by modified plasmids or viral vectors (e.g. adeno-associated virus); once it is within the cells, the light pulse stimulation will “activate” the cells with the opsin we transfected the cells with.

Applications: drug discovery (by target identification), elicit seizures for epilepsy research, mind-controlled transgene expression

References and bibliography of interest:

Gholami Pourbadie, H. & Sayyah, M. (2018). Optogenetics: Control of Brain Using Light. Iranian biomedical journal 22, 4–5

Deisseroth, K. (2010). Optogenetics. Nature Methods 8, 26 – 29

Folcher, M., Oesterle, S., Zwicky, K. et al. (2014) Mind-controlled transgene expression by a wireless-powered optogenetic designer cell implant. Nat Commun 5

Dieter, A., Keppeler, D., & Moser, T. (2020). Towards the optical cochlear implant: optogenetic approaches for hearing restoration. EMBO molecular medicine 12

Zhang, H., & Cohen, A. E. (2017). Optogenetic Approaches to Drug Discovery in Neuroscience and Beyond. Trends in biotechnology 35, 625–639

Cela, E. & Jesper, P. (2020). A Step-by-Step Protocol for Optogenetic Kindling. Front. Neural Circuits 14 (3)

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References:

Mousavizadeh, L. & Ghasemi, S. (2020). Genotype and phenotype of COVID-19: Their roles in pathogenesis. Journal of Microbiology, Immunology and Infection.

Hulswit, R.J.G. & Bosch, B.J. (2016). Chapter Two: Coronavirus Spike Protein and Tropism Changes. Advances in Virus Research 96, 29 – 57.

Gelderblom, H.R. (1996). Structure and Classification of Viruses. In: Baron, editor. Medical Microbiology 4th edition. Chapter 41