Living in a microbial world Sarah Lloyd examines the importance of bacteria in the origin of life.
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All animals and plants owe their existence to this chance mutation in a single bacterium billions of years ago. Even today we rely on bacteria to ensure our planet is hospitable. Nitrogen, the most abundant gas in our atmosphere, makes up 78% of all the air we breathe and all organisms need it to grow. However, in its natural form, it is useless to both animals and plants. Instead, we rely on nitrogen-fixing bacteria to convert it into different forms that we can use, like ammonia and nitrates. As well as looking after our planet, bacteria also aid human survival. This statement may sound “It is becoming increasingly clear strange given the multithat our lives are inextricably linked tude of bacteria-borne diseases. However, of the with bacteria.” numerous bacterial spehospitable. However, within the hot cies on the planet, only around 150 are hydrothermal vents of the newly pathogenic. The rest are relatively formed oceans, bacteria were born, and harmless, and some have even been seen to benefit humans. life began. Trillions of bacteria reside within For over a billion years, bacteria continued to grow and evolve. As the our body. These bacteria have debacteria replicated, copying errors veloped a mutual relationship with huwithin their genetic code led to muta- mans: they rely on us for a space to live tions. One such mutation – believed to protected from the outside world, and have happened 2.4 billion years ago – in return they provide humans with created a new species of bacteria that many functions that we need but are could harness energy from the sun to unable to do ourselves. And not just split apart water molecules, releasing humans, bacteria have evolved an oxygen into the atmosphere. This pro- astounding range of intimate relationcess, known as photosynthesis, enabled ships with almost every animal on the oxygen-dependent life forms to exist. planet. ong before humans arrived on Earth, the planet was ruled by microbes. Although individually insignificant, when taken together, these organisms make a formidable force. It was bacteria that shaped the planet to create the current world we now live in; life as we know it would not be possible without them. When bacteria first emerged over 3.5 billion years ago, the world’s atmosphere was a far cry to how it is today. A thick, black layer of dried lava covered the ground, while sweeping gusts of acidic vapours swirled under an orange sky – in other words, very in-
10 | SATNAV | June 2021
