Microorganisms used in research have many useful properties. They grow on simple, cheap medium and often give rise to large populations in a matter of 24 hours. It is easy to isolate their genomic material, manipulate it in the test tube and then place it back into the microbe. Due to their large populations it is possible to identify rare events and then, with the use of powerful selective techniques, isolate interesting bacterial cells and study them. These advantages have made it possible to test hypotheses rapidly. Using microbes scientists have expanded our knowledge about life. Below are a few examples.
Microorganisms have been indispensable instruments for unlocking the secrets of life. The molecular basis of heredity and how this is expressed as proteins was described through work on microorganisms. For an in-depth discussion on the molecular basis of heredity see the chapter on the Central Dogma. Due to the similarity of life at the molecular level, this understanding has helped us to learn about all organisms, including ourselves.
Some prokaryotes are capable of growing under unimaginably harsh conditions and define the extreme limits of where life can exist. Some species have been found growing at near 100 °C in hot springs and well above that temperature near deep-sea ocean vents. Figure 1-19 depicts such a deep sea ocean vent. Others make their living at near 0 °C in freshwater lakes that are buried under the ice of Antarctica. The ability of microbes to live under such extreme conditions is forcing scientists to rethink the requirements necessary to support life. Many now believe it is entirely possible that Jupiter's moon Europa may harbor living communities in waters deep below its icy crust. What may the rest of the universe hold?
A deep sea ocean vent
Figure 1.19 A deep sea ocean vent. Ocean vents are common in areas of the sea floor that have volcanic activity. Water seeps into cracks on the floor and encounters magma. The water absorbs inorganic nutrients from the magma and is heated. The superheated water then flows out of the magma, sometimes quite forcefully, back into the ocean. This hot water contacts the cold ocean water, causing it to cool and release many of its inorganic contents. This cloud of inorganic compounds is highly reduced and can serve as a source of energy for microorganisms. These microbes serve as a primary producer for an entire food chain. The picture shows one type of ocean vent called a black smoker. Water coming out of the vent can be >300°C. Figure courtesy of Woods Hole Oceanic Institute.
Until recently, while we could study specific types of bacteria, we lacked a cohesive classification system, so that we could not readily predict the properties of one species based on the known properties of others. Visual appearance, which is the basis for classification of large organisms, simply does not work with many microbes because there are few distinguishing characteristics for comparison between species even under the microscope. However, analysis of their genetic material in the past 20 years has allowed such classification and spawned a revolution in our thinking about the evolution of bacteria and all other species. The emergence of a new system organizing life on Earth into three domains is attributable to this pioneering work with microorganisms.
The fruits of basic research on microbes have been used by scientists to understand microbial activity and therefore to shape our modern world. Human proteins, especially hormones like insulin and human growth factor, are now produced in bacteria using genetic engineering. Our understanding of the immune system was developed using microbes as tools. Microorganisms also play a role in treating disease and keeping people healthy. Many of the drugs available to treat infectious disease originate from bacteria and fungi.
Lastly, microbes have informed us about our world through the tools they provide for molecular biology. Enzymes purified from bacterial strains are useful as tools to perform many types of analyses. Such analyses allow us to determine the complete genome sequence of almost any organism and manipulate that DNA in useful ways. We now know the entire sequence of the human genome, with the exception of regions of repetitive DNA, and this will hopefully lead to medical practices and treatments that improve health. We also know the entire genome sequences of hundreds of microbes, including those of many important pathogens. Analysis of these data will eventually lead to an understanding of the function of critical enzymes in these microbes and the development of tailor-made drugs to stop them. The tools of molecular biology will also affect agriculture. For example, we now know the complete genome sequence of the plant Arabidopsis (a close relative of broccoli and cauliflower). This opens a new avenue to a better understanding of all plants and hopefully improvements in important crops.
Microbes have a profound impact on every facet of human life and everything around us. Pathogens harm us, yet other microbes protect us. Some microbes are pivotal in the growth of food crops, but others can kill the plants or spoil the produce. Bacteria and fungi eliminate the wastes produced in the environment, but also degrade things we would rather preserve. Clearly they affect many things we find important as humans. In the remainder of this chapter we take a look at how scientists came to be interested in microbes and follow a few important developments in the history of microbiology.
Microorganisms used in research have many useful properties. They grow on simple, cheap medium and often give rise to large populations in a matter of 24 hours. It is easy to isolate their genomic material, manipulate it in the test tube and then place it back into the microbe. Due to their large populations it is possible to identify rare events and then, with the use of powerful selective techniques, isolate interesting bacterial cells and study them. These advantages have made it possible to test hypotheses rapidly. Using microbes scientists have expanded our knowledge about life. Below are a few examples.
Microorganisms have been indispensable instruments for unlocking the secrets of life. The molecular basis of heredity and how this is expressed as proteins was described through work on microorganisms. For an in-depth discussion on the molecular basis of heredity see the chapter on the Central Dogma. Due to the similarity of life at the molecular level, this understanding has helped us to learn about all organisms, including ourselves.
Some prokaryotes are capable of growing under unimaginably harsh conditions and define the extreme limits of where life can exist. Some species have been found growing at near 100 °C in hot springs and well above that temperature near deep-sea ocean vents. Figure 1-19 depicts such a deep sea ocean vent. Others make their living at near 0 °C in freshwater lakes that are buried under the ice of Antarctica. The ability of microbes to live under such extreme conditions is forcing scientists to rethink the requirements necessary to support life. Many now believe it is entirely possible that Jupiter's moon Europa may harbor living communities in waters deep below its icy crust. What may the rest of the universe hold?
A deep sea ocean vent
Figure 1.19 A deep sea ocean vent. Ocean vents are common in areas of the sea floor that have volcanic activity. Water seeps into cracks on the floor and encounters magma. The water absorbs inorganic nutrients from the magma and is heated. The superheated water then flows out of the magma, sometimes quite forcefully, back into the ocean. This hot water contacts the cold ocean water, causing it to cool and release many of its inorganic contents. This cloud of inorganic compounds is highly reduced and can serve as a source of energy for microorganisms. These microbes serve as a primary producer for an entire food chain. The picture shows one type of ocean vent called a black smoker. Water coming out of the vent can be >300°C. Figure courtesy of Woods Hole Oceanic Institute.
Until recently, while we could study specific types of bacteria, we lacked a cohesive classification system, so that we could not readily predict the properties of one species based on the known properties of others. Visual appearance, which is the basis for classification of large organisms, simply does not work with many microbes because there are few distinguishing characteristics for comparison between species even under the microscope. However, analysis of their genetic material in the past 20 years has allowed such classification and spawned a revolution in our thinking about the evolution of bacteria and all other species. The emergence of a new system organizing life on Earth into three domains is attributable to this pioneering work with microorganisms.
The fruits of basic research on microbes have been used by scientists to understand microbial activity and therefore to shape our modern world. Human proteins, especially hormones like insulin and human growth factor, are now produced in bacteria using genetic engineering. Our understanding of the immune system was developed using microbes as tools. Microorganisms also play a role in treating disease and keeping people healthy. Many of the drugs available to treat infectious disease originate from bacteria and fungi.
Lastly, microbes have informed us about our world through the tools they provide for molecular biology. Enzymes purified from bacterial strains are useful as tools to perform many types of analyses. Such analyses allow us to determine the complete genome sequence of almost any organism and manipulate that DNA in useful ways. We now know the entire sequence of the human genome, with the exception of regions of repetitive DNA, and this will hopefully lead to medical practices and treatments that improve health. We also know the entire genome sequences of hundreds of microbes, including those of many important pathogens. Analysis of these data will eventually lead to an understanding of the function of critical enzymes in these microbes and the development of tailor-made drugs to stop them. The tools of molecular biology will also affect agriculture. For example, we now know the complete genome sequence of the plant Arabidopsis (a close relative of broccoli and cauliflower). This opens a new avenue to a better understanding of all plants and hopefully improvements in important crops.
Microbes have a profound impact on every facet of human life and everything around us. Pathogens harm us, yet other microbes protect us. Some microbes are pivotal in the growth of food crops, but others can kill the plants or spoil the produce. Bacteria and fungi eliminate the wastes produced in the environment, but also degrade things we would rather preserve. Clearly they affect many things we find important as humans. In the remainder of this chapter we take a look at how scientists came to be interested in microbes and follow a few important developments in the history of microbiology.
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