[Lecture] Microbiology Class

Today, we're going to talk about chemosynthesis, which is more of a recent theory of how certain forms of life may exist on the Earth. It is common knowledge that any form of life needs the energy to maintain its existence, and most life on the Earth, particularly plant species, relies on photosynthesis, the process that generates energy from sunlight. And for a long time, scientists believed that at the bottom of the food chain, all life depended on energy only from this process. Consequently, they believed that life could only exist where sunlight penetrated. There had been no evidence to give us reason to think otherwise until quite recently.
    think otherwise = think differently
    

In the 1970s, however, scientists discovered various forms of life around hydrothermal vents on the floor of the Pacific Ocean where no sunlight can penetrate. A hydrothermal vent is basically a spring of hot water on the deep ocean floor. It has been discovered by researchers that a unique ecosystem has evolved around these vents in the absence of sunlight, and to their surprise, its source of energy is completely different. They learned that primitive bacteria form the basis of this living community and that the bacteria derive their energy from a process called 'chemosynthesis.' Of course, being under the deep ocean where sunlight can't reach, this process did not comply with our previous understanding of the energy sources of life.

So, chemosynthesis can be defined as the process by which certain types of microorganisms create energy through chemical reactions with the minerals from the hydrothermal vents. In terms of geography, this process is associated with the midoceanic ridge and rift systems, where the thin plates of the earth's crust are spreading, creating the vents. Seawater seeps through, becoming saturated with minerals and chemicals such as hydrogen sulfide and heated to high temperatures. The water is then emitted through the cracks as dark black geysers that sort of resemble a black chimney emitting smoke in the dark. Actually, this is how they get the name 'black smokers.' Then, it is quickly cooled to a warm 23-degree Celcius. So, the immediate area around these hydrothermal vents actually becomes a warm and fertile environment, with clumps of primitive microorganisms, like archaea, provide the foundation for the biological colonization of vents. They generally live on or below the seafloor. Actually, some of them even form symbiotic relationships with other vent animals and live as symbionts within the bodies of these animals. Now, the researchers are becoming even more fascinated by a great variety of deep-sea animal species such as clams, crabs and giant tubeworms, that all rely on chemosynthetic microorganisms!
    clumps: cluster, group, mass, bunch

However, even with chemosynthesis as a source of energy, conditions in the deep sea are hostile. Well, think about it. Not only are the pressures in the area at least 200 times greater than the atmospheric pressure at sea level, but it is also the site of frequent volcanic eruptions and earthquakes. As you can imagine, it's a rather volatile environment for any ordinary life forms. So, we can reasonably assume that for any organism to flourish under these conditions, it must possess unusual biological traits with which we are not yet familiar.
    volatile: being likely to change suddenly and unexpectedly; changeable, shifting, variable, unsettled

Now, it is clear that there is so much more to be discovered about deep-ocean life. In fact, the amount of exploration of the mid-ocean ridge system of our Earth is significantly less than the exploration of other planets. It is estimated that perhaps less than 0.1 percent of the mid-ocean ridge has been explored so far. So, throughout your studies, keep in mind that no matter what measure is used, a much greater portion of the earth's body is still waiting to be explored. And, I can assure you, you're in for a lot of surprises.