The most widely employed methods for classifying microbes are morphological characteristics, differential staining, biochemical testing, DNA fingerprinting or DNA base composition, polymerase chain reaction, and DNA chips. Assess the characteristics of pre-life earth and which adaptations allowed early microbial life to flourish.
Scientific evidence suggests that life began on Earth some 3. Since then, life has evolved into a wide variety of forms, which biologists have classified into a hierarchy of taxa. Some of the oldest cells on Earth are single-cell organisms called archaea and bacteria. Fossil records indicate that mounds of bacteria once covered young Earth.
Some began making their own food using carbon dioxide in the atmosphere and energy they harvested from the sun. Soon afterward, new oxygen-breathing life forms came onto the scene.
With a population of increasingly diverse bacterial life, the stage was set for more life to form. There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells. This evidence is described in the endosymbiotic theory. Symbiosis occurs when two different species benefit from living and working together. The endosymbiotic theory describes how a large host cell and ingested bacteria could easily become dependent on one another for survival, resulting in a permanent relationship.
Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell. Mitochondria and chloroplasts have striking similarities to bacteria cells. And both organelles use their DNA to produce many proteins and enzymes required for their function. A double membrane surrounding both mitochondria and chloroplasts is further evidence that each was ingested by a primitive host.
The two organelles also reproduce like bacteria, replicating their own DNA and directing their own division. It is passed down directly from mother to child, and it accumulates changes much more slowly than other types of DNA. Because of its unique characteristics, mtDNA has provided important clues about evolutionary history. For example, differences in mtDNA are examined to estimate how closely related one species is to another.
Conditions on Earth 4 billion years ago were very different than they are today. The atmosphere lacked oxygen, and an ozone layer did not yet protect Earth from harmful radiation. Heavy rains, lightning, and volcanic activity were common. Yet the earliest cells originated in this extreme environment. Extremophiles archaea still thrive in extreme habitats.
Astrobiologists are now using archaea to study the origins of life on Earth and other planets. Because archaea inhabit places previously considered incompatible with life, they may provide clues that will improve our ability to detect extraterrestrial life.
Interestingly, current research suggests archaea may be capable of space travel by meteorite. Such an event termed panspermia could have seeded life on Earth or elsewhere. The presence of archaea and bacteria changed Earth dramatically. They helped establish a stable atmosphere and produced oxygen in such quantities that eventually life forms could evolve that needed oxygen.
The new atmospheric conditions calmed the weather so that the extremes were less severe. Life had created the conditions for new life to be formed. This process is one of the great wonders of nature. Microbes are ubiquitous on Earth and their diversity and abundance are determined by the biogeographical habitat they occupy. Summarize how microbial diversity contributes to microbial occupation of diverse geographical niches.
Bacteria and archaea have also been found near deep-sea hydrothermal vents, which is an environment with extremely high temperatures and tremendous pressure. As well as at the bottom of the ocean, bacteria have been discovered in ancient ice in Alaska. These microbes that can survive extreme environments are called extremophiles and are useful in industrial processes because they can catalyse reactions in harsh conditions.
For example, the archaea Sulfolobus solfataricus is used to break down dangerous organophosphorus compounds, and as it is used to living in volcanic pools, this microbe is very robust.
Microbes have even been found in the clouds, where they can help the clouds precipitate to make rain or snow. For a cloud to produce rain or snow, there needs to be tiny particles which serve as a nuclei for condensation. Often, these particles are of mineral origin, but airborne microbes have been found to do this job too, and some microbes have adapted to withstand UV radiation, enabling them to survive in the atmosphere.
Streptomyces are one-such soil-dwelling bacteria which produce antibiotics, these are chemical substances used to fight off competing bacteria.
Another interesting thing about Streptomyces , is that they produce a compound called geosmin which is behind the smell produced when rain hits soil.
The cells are described as prokaryotic because they lack a nucleus. They exist in four major shapes: bacillus rod shape , coccus spherical shape , spirilla spiral shape , and vibrio curved shape. Most bacteria have a peptidoglycan cell wall; they divide by binary fission; and they may possess flagella for motility. The difference in their cell wall structure is a major feature used in classifying these organisms.
According to the way their cell wall structure stains, bacteria can be classified as either Gram-positive or Gram-negative when using the Gram staining. Bacteria can be further divided based on their response to gaseous oxygen into the following groups: aerobic living in the presence of oxygen , anaerobic living without oxygen , and facultative anaerobes can live in both environments. According to the way they obtain energy, bacteria are classified as heterotrophs or autotrophs.
Autotrophs make their own food by using the energy of sunlight or chemical reactions, in which case they are called chemoautotrophs. Heterotrophs obtain their energy by consuming other organisms. Bacteria that use decaying life forms as a source of energy are called saprophytes. Archaea or Archaebacteria differ from true bacteria in their cell wall structure and lack peptidoglycans.
They are prokaryotic cells with avidity to extreme environmental conditions. Based on their habitat, all Archaeans can be divided into the following groups: methanogens methane-producing organisms , halophiles archaeans that live in salty environments , thermophiles archaeans that live at extremely hot temperatures , and psychrophiles cold-temperature Archaeans.
So interesting 31 Oct, The videos were useful and I felt it gave me a good introduction and foothold on the subject of microbiology This introductory level course w Glyn Barrett and all the other professors at the University of Reading who have been a It was a good introduction 26 Jun, Lots of interesting facts and 18 Oct, Lots of interesting facts and videos from leaders in specific areas of research.
This course was a really 29 Aug, In addition, the small quizzes in the course aided I liked the title as it helped m I have learned quite a lot from this course as someone who is new An excellent introduction to mir The course consists of Microbes are organisms that are too small to be seen with the unaided eye. They evolved long before the first plants and animals appeared and affect our lives in more ways than we might expect.
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