What is carbon? “Which one of the Pancha Bhuta does this belong to?” asks an elderly gentleman. Sanjana Hegde, mediator, Science Gallery Bengaluru (SGB), who was somewhat surprised by the question, explains that carbon could be any of them in different forms. The gentleman, however, doesn’t give in to this all-in-one identity of carbon. He thinks that’s preposterous! That can’t be true. He asks again, “No, you tell me, is it Vayu or Prithvi?” Further questions and answers take this discussion on for about 20 minutes at the Indiranagar Metro Station, where the Jīvāṇu exhibit of SGB’s exhibition CARBON has been placed for display from August to October 2023, Wednesdays to Sundays at 3 – 7 pm.
In Carbon, SGB brings forth thought-provoking questions about the element from the beginning of this earth to the present day,
How do we understand carbon beyond the catchphrases and contradictions? Why does it behave the way it does — the elemental basis for life but equally a gas capable of suffocating life?
Origins of life
Life is thought to have arisen from non-living matter in a natural process using simple organic compounds formed from inorganic chemicals abundant in the prebiotic earth. In 1952, Stanley Miller and Harold Urey carried out an experiment to demonstrate that many of the “molecules of life” such as amino acids can arise in fairly simple laboratory conditions. In their study, the scientists used an oxygen-less mixture of gases, methane, ammonia, hydrogen, and water vapour inside a glass vessel, along with electrical discharges, demonstrating the formation of organic molecules like amino acids, which are building blocks of proteins. Alexander Oparin and JBS Haldane had earlier proposed (in the 1920s) that such molecules can concentrate into droplets, known as coacervates, which might have acted as precursors of present day cells (protocells) but there has been no such demonstration to date.
Around the same time that Miller and Urey were carrying out their experiments at the University of Chicago in the USA, two of their Indian contemporaries also started walking a similar path. In the 1950s, Krishna Bahadur and his wife, S Ranganayaki, at the Department of Chemistry, University of Allahabad set out to explore the possible emergence of life from a mixture of compounds, such as paraformaldehyde, ferric chloride, potassium nitrate, ammonium phosphate, water, molybdenum dioxide, sodium chloride, etc., performing the experiment under sunlight or artificial light. They found some spherical particles were created by keeping this mixture under light for days to weeks. These particles were dubbed as Jeewanu in the team’s publications in the 1960s, which also claimed that the Jeewanu could grow and divide. Using the analytical methods of the day, claims of the formation of amino acids and the ability of these particles to fix nitrogen, which is common among microorganisms, were also made. If indeed true, this would represent a real milestone in the quest for the emergence of life-like traits from simple chemical mixtures.
Over half a century later, Shashi Thutupalli, Associate Professor, NCBS and International Centre for Theoretical Sciences, Bengaluru, together with his students, Nayan Chakraborty and others, are revisiting this research project using modern analytical tools and microscopy. Their aim is to rigorously establish (or refute) the claims from the original experiments. The inquiries focus on these fundamental questions: Do the Jeewanu particles exhibit the claimed properties of growth and division? What are these particles composed of and are they indeed permeable compartments? Can they metabolise and produce more complex molecules such as amino acids?
“There is debate around the interpretations of the results of the Jeewanu experiments, and very few investigations have been carried out to follow up on Krishna Bahadur’s work. The original research project seems to have been either lost or forgotten or both. No labs around the world built up on that work,” says Nayan. While reviewing the literature, the Bengaluru team found that although a review from NASA questioned most of the claims of this work, it was not based on reproduced experiments but rather only on a reading of Bahadur and Ranganayaki’s published works. The report dismissed the results stating that the evidence provided was not sufficient for the claims and that the methods were not described in sufficient detail to allow for replication of the experiments. In sum, rigorous tests to either refute or confirm the claims by systematic replication have not yet been performed.
Past experiments vs. current findings
The initial goal of this project in Thutupalli lab was to check whether (and which of) Bahadur and Ranganayaki’s claims were reproducible. In a real tour de force, guided by the intuition of a chemist, Nayan managed to revive the experimental protocols and got the experiments running to establish the formation of Jeewanu-like structures.
Although Bahadur and Ranganayaki used multiple ingredients to create the particles, the NCBS scientists first wanted to zero down the minimal requirements for this experiment. They found that only some ingredients mentioned in the previous work were necessary to form the particles. As expected, the carbon source — paraformaldehyde, was essential, along with molybdenum, ammonium phosphate, and iron sulphate, to create the particles. Even light isn’t crucial, as it just catalyses the reaction, helping in the faster formation of the Jeewanu particles.
Armed with these results, the team is now moving ahead with various ongoing measurements and analyses to verify the various claims. The first two claims of Bahadur’s work were that these particles can grow and divide through budding. In biology, budding represents a form of asexual reproduction where one organism is formed from a bud of an existing organism. “When we tracked a few Jeewanu particles continuously under the microscope, we could see that they grow — in that sense, Krishna Bahadur was correct, but our experiments have not yet revealed budding. From our experiments we see when the particles grow at high densities, they grow into each other, producing structures like those in the images obtained by the Allahabad team which may have been wrongly interpreted as proof of budding,” says Nayan. As of now, Thutupalli’s team has only confirmed the growth of the particles, but not their budding or division. It is possible that Bahadur and Ranganayaki could have misinterpreted the images or there may indeed be other (as yet unexplored) conditions in which such budding is possible — after all, the claims of the Allahabad team were made on the basis of three decades of work, much of which may not be described in sufficient detail.
The third original claim was of metabolism by the Jeewanu particles. Bahadur used paper chromatography to claim that amino acids were being formed in the mixture. Instead of this low sensitivity analytical method, Thutupalli’s group has been using mass spectrometry to identify molecules in the mix based on their unique mass-to-charge ratio. “Very preliminary mass spectrometry results seem to suggest that the Allahabad team might indeed have been on the right track. We do see some signatures of amino acids and other small chemical molecules in our measurements,” says Nayan. However, as it is a preliminary result addressing an important claim, the results remain to be established beyond any doubt. The team is now performing such further experiments to unambiguously identify which compounds are formed and in what amounts.
Like all living cells, Bahadur and Ranganayaki claimed these particles also acted as compartments. For the particles to act as compartments, they must have a membrane or structure around them that is ‘permeable’ — some substances can go inside these particles, and others can be sent out. “It’s not typical that all spherical-looking objects be permeable. Precipitates — a highly condensed state — are not permeable, whereas lipid vesicles or micelles can be permeable,” explains Nayan. This brings us to the question of what makes up the Jeewanu particles. Experiments to investigate this are currently underway.
“If Jeewanu is indeed proven to be a primitive version of a protocell, it might be one of the simplest or minimal protocell to date, as all other protocell models in the field use complex molecules like polymers instead of simple molecules,” explains Nayan. For the moment however, the Bangalore team is moving ahead with a mix of caution and optimism.
Public engagement in Carbon
Pranav Bidare, a technology and law researcher who visited the Jīvāṇu exhibit at the Indiranagar Metro Station, says, “The primordial soup exhibit is not what I expected. Mostly, when people speak about carbon, they think of either carbon emissions and pollution or organic chemistry and things like that. But how essential it was in creating life itself is not something people think about.” He adds,
SGB is doing a good job of bringing both the positive and negative things to light. I am only hoping that whatever awareness or change in public opinion this creates will lead to something concrete that will change people’s policies or bring something good to the environment.
Puja Das, an SGB mediator for CARBON, finds it specifically “interesting that Science Gallery Bengaluru is bringing an ongoing experiment to the public. Most of the time, exhibitions are put forth when all the experiments of a project have been completed. Only then is it publicised. But right now, having this engagement where people get to know that it is an ongoing experiment makes it all the more interesting for conversations.”
Exhibits of CARBON are being showcased until October at Indiranagar, Majestic, MG Road, and Sandal Soap Factory Metro Stations before the final exhibition is unveiled later this year. Passengers of all ages from across the city come to visit these exhibits. “We see a mixture of crowd. On weekends, especially at the MG Road and Indiranagar Metro Stations, we primarily see a younger crowd. We see a slightly older crowd in other places like Majestic and Sandal Soap Factory Metro Stations. Still, it’s interesting that even they are curious about it,” says Parvathy P Sekhar, an SGB mediator for CARBON.