There are two truths about life beyond the philosophical. First, we live in a microbial world. By microbes, we mean the class of organisms that are generally not visible to the naked eye. Among these are bacteria, single-celled organisms different in many ways to other single-celled organisms such as yeast and the trillions of cells that come together to make us human. Bacteria, considered simpletons, are by far the most predominant form of free-living life known on this planet. There has been an estimate that the number of bacteria on earth should be around one followed by thirty zeros; I’m not sure what that number should be called.
In the human imagination, many bacteria are a nuisance and in the worst cases are to be feared. There are many infectious diseases on this planet, the cause of much morbidity and mortality, that are caused by bacteria. On the other hand, it is also true that we wouldn’t exist the way we do in a world devoid of these bacteria. It is a cliched phrase now that a human body carries ten-times as many bacterial cells as human cells, and that experimental animals that are devoid of these regular inhabitants of their body have serious trouble leading a normal life. As an example, the diarrhoea that we end up with after a dose of some choice antibiotics can be attributed to the purging of these friendly inhabitants from our guts; hence the routine of being prescribed a probiotic – a cluster of friendly bacteria – alongside some antibiotics.
It’s probably true that if I randomly sampled 10 bacteria, none of these would cause disease in a healthy human. Away from the stiflingly anthropogenic view of life, bacteria also catalyse many biogeochemical reactions on the planet and so play a major role in making the world the place it is. In this series of articles, we will discuss the bacterial way of life, how they are a cornerstone of the ecosystems we live in, and how some of our dealings with these organisms result in distress.
The second truth of life that concerns us is genetics. The essence of life, as posited by the tenets of evolution, is the technical term called fitness: not quite determined by the number of hours spent in the gym but something more mundane, the ability of an individual to produce viable progeny. All forms of life do this though the rate at which they do so differs among organism types. For example, a population of 100 bacterial cells of the type Escherichia coli might double in number in 20 minutes, a number which is referred to as its generation time. On the other hand, a pair of humans might produce one or two offsprings over an entire lifetime spanning a good part of a century. And we all coexist; understanding how the coexistence of such a diverse array of organisms comes about is in itself an exciting and challenging field of research (but this won’t be dealt with extensively in this series). Note that this comparison of reproduction rates, between the single-celled bacterium and a large human, is not entirely fair – and ‘why’ is for another day. For now it suffices to say that the term that is critical to the continuity of life, irrespective of whether the species is propagated every 20 minutes or every 20 years, is reproduction.
We all know that a crucial factor in determining who we are is our genome, our genetic material. Not only does it determine many of our traits, it also encodes features that ensure it is replicated faithfully and transmitted from one generation to the next. While important in ensuring the continuity of life, fidelity, which ensures an accurate replication of genetic material, shouldn’t be too good. If it were so, we would all have been the same: from bacteria to guppies to humans. A certain level of mutation from one generation to the next is essential for life the way we know it. And this is non-negotiable if we had to have evolved – and we do evolve. Bacteria are masters of this art and their finding of a balance between being accurate as well as being sufficiently sloppy to generate enough variability has gone a long way in keeping them going, from finding a way to survive in every corner of the earth to defeating antibiotics.
This series will bring together a collection of general science articles on the genetics of bacteria. We’ll see how the study of bacteria has informed the way we understand continuity of life; how knowing bacterial genetics is critical from a medical perspective, in terms of how a small minority of bacteria become agents of disease and how they evade the vast array of weapons we throw at them. While the objective is to present the spectrum of science in this field to the general public, I’ll also take the opportunity, where possible, to make a pitch for basic science and leave readers to draw their own conclusions from the stories in these articles.
Much of our current understanding of bacterial biology came about not by a blinkered vision of applied research but from decades of attempting to answer fundamental questions. These questions have been pursued by many researchers from around the world, and their efforts have incremented our knowledge and understanding one research paper or thesis after another. The “innovation” buzzword doesn’t appear out of nowhere and is largely grounded on the strong foundations laid by basic science. There have also been many instances where studies with goals of direct relevance to our society influenced more abstract questions driven by curiosity, which is a necessary human characteristic. While applied research with a mission is of great importance, this cannot exist without an understanding of the fundamental aspects of science.
These are not issues that many of us deliberate on in our everyday lives, but in the face of public and political scepticism of funding basic science, the time is ripe to think about the place of fundamental science in society.
Aswin Sai Narain Seshasayee runs a laboratory researching bacterial biology at the National Centre for Biological Sciences, Bengaluru. Beyond science, his interests are in classical art music and history.