This is the domain of microbial ecology, which spun off from microbiology long ago but acquired speed only recently. While the parent science is founded on taxonomy, the ordering of life forms into genus, species, variety and strain, microbial ecology looks at organisms in the context of the minute ecosystems they inhabit, and studies how they interact with each other and with other life forms, such as humans.
Bacteria and fungi have been used in the food and beverage industry for millennia, and the study of Penicillium altered the practice of medicine altogether. Recent innovations include the use of hydrocarbonoclastic bacteria like Thalassolituus and Alcanivorax to degrade oil spills, but the economic possibilities have barely been tapped. Though microbes are the most numerous life forms a pinch of soil may contain tens of millionsonly a small minority have been studied exhaustively. If the proteins of one microbe trigger asthma, another may prevent attacks. While some bacteria crack oil spills, so far unappreciated species could clean up the interiors of refrigerators and cars, storehouses of infection in modern times. Forensics can get a leg up with the recent discovery, at the University of Colorado at Boulder, that our fingertips leave behind personal microbial signatures on objects they touch. This could find use in the courtrooms and police labs of the near future, supplementing the use of fingerprints and genetic material.
The idea of using microbes, usually bacteria, to better our lives could be as old as human civilisation. By Roman times, fermented foods were a permanent feature of European cuisine. Wine and cheese were promoted for their health benefits and the Romans especially prized a fish sauce called garum. Made from fish guts fermented in sunlit sea water, it had to be produced in factories far away from human habitations for reasons of public sanitation and even sanity, but appeared to have medicinal qualities nevertheless.
The technologies of fermented food and drink derived from artisanal traditions and were probably developed in the commons by trial and error, without a clear understanding of the science involved or possible health benefits. That changed shortly after 1903, when Nobel laureate Elie Metchnikoff gave a name to the study of ageinggerontology. Four years later, he attributed the ageing process to bacteria like Clostridium which live in the gut and break up proteins to release toxins like ammonia and phenols. These produced the effects seen in the ageing process, he suggested.
Metchnikoff had noted that certain rural communities in the Russian Imperium and eastern Europe, whose diet was based on milk fermented by lactic acid bacteria like Lactobacillus, were generally long-lived. He suggested that infusing the human gut with living lactic acid bacteria would contain the insalubrious by-products of protein-crunching bacteria. In fact, lactic acid bacteria create an acidic medium in the gut, which inhibits the toxin-producers. That was the beginning of the preoccupation with probiotics or life-enhancers, which is almost a craze today.
The idea of probiotics was monetised in 1935 by Minoru Shirota, who launched a yoghurt-like drink which included a strain of Lactobacillus casei which he had cultured at Kyotos Imperial University School of Medicine, and which was later named the Shirota strain. Today, Yakult is a listed company, a brand as widely recognised as Nissan and Nakamichi, and brings in revenues of $3.5 billion. It has triggered a secondary market in dehydrated probiotics from the pharmaceutical industry, which are prescribed with oral antibiotics.
Microbial ecology has picked up speed in recent years because of gene sequencing. Microbes can be classified by the thousands in the kind of time it used to take to place individual species in their family trees by describing their properties. It has become practical to seek microbes in bulk, even from hitherto unexploited habitatsthe atmosphere, volcanic vents in the sea, digestive systems of insects, the human armpit.
The last is of immediate commercial value, promising to spur growth in the global deodorant industry, which has been growing anyway since 2006 because of ever-earlier adoption among young people. But far more rewarding opportunities probably lie in the realm of the unknown, and will be identified in the future by mining the vast volumes of data now being generated on newly catalogued microbial life. At the very least, microbes are likely to become the janitors of the future, cleaning artificial habitats like space stations more efficiently than machines. And microbial processes yet unidentified could spawn something even bigger than the probiotic industry kick-started by Yakult 80 years ago.