Editors’ note: This is the introductory post to the series ‘Bacterial Expressions‘ by Dr. Aswin Sai Narain Seshasayee on the fundamentals of molecular biology, microbiology and biochemistry underlying bacterial evolution.
Bacteria are everywhere, from the soil by our doorstep to the hottest thermal vents. They happen to be the predominant form of free-living life on this planet, with a population numbers of one followed by thirty zeros being bandied about. Even anthropocentrically, it has become cliched to state that the human body plays host to ten times as many bacterial cells as human cells, and that we will cease to exist in the absence of these creatures. Of course I do not have to make a mention of the flip side of being with bacteria – the numerous infectious diseases ranging from strep throat through tuberculosis to gastric cancer. But we may be best served by remembering that these disease-causing germs are only a minuscule fraction of all the bacteria that are there.
Many bacteria are obligate symbionts: they are dependent on their hosts for their survival, and in many cases where the host is biotic, the host and the bacterium have co-evolved such that their complementarity is astounding. At the other extreme are bacteria capable of surviving in many diverse habitats and in fact dominating them; their metabolic capabilities and the manner in which these abilities are regulated at the spatio-temporal level are remarkable.
It is not just a matter of metabolising nutrients; it is also a matter of facing up to stresses, from well, nutrient starvation, to evading the immune system of a large, well-accoutered host, to tacking toxicity of killing agents in the environment including those thrown at them by us in the form of antibiotics. And, just as we have a problem with viruses, so do bacteria, having to get around the problem posed in the form of predatory viruses called bacteriophages (or phages for short).
But bacteria have seen them all, and beaten most of them, and have learned to co-exist with others. It is a case of been there, done that for most bacteria. The objective of this series of articles is to present some fundamentals of molecular biology, microbiology and biochemistry, and to use this knowledge to present mechanisms by which bacteria evolve and how through genetic changes and transient regulatory mechanisms they approach the simple matter of taking over the big, bad world around them!
Readers are directed to the following website for interesting material on bacteria and microbes in general: http://www.microbeworld.org/