Bacteria are diminutive microscopic organisms which can be found in numerous environments. They are simple life forms. Bacteria is part of the Monera Kingdom. These organisms have certain characteristics. They have a single celled structure, are microscopic in size, and do not possess a nucleus. The DNA of Monera remains loose in the cell, therefore making it prokaryotic. Monera are not plants nor animals, but are classified as either being bacteria or blue-green algae. There are known to be close to 4,000 different species of Monera. It is possible that these were the first organisms to emerge on Earth. Not all bacteria is harmful. The skin can carry up to a total 600 million bacteria. Every single one does not induce disease, but it is possible more lethal microorganisms can enter the body. Diphtheroids are present in moist areas of the body like the arm pits and groin. Saliva can carry streptococci, spirochetes, fusobacteria, and bacilli. The large bowel has escherichia coli and clostridia. Bacteria has proven to be a survivor and a successful species in the Earth's ecosystem.
The size of bacteria is minimal. This however allows it to adapt to other environments more efficiently. Thirty trillion bacteria of standard size can only weigh as much as 28 grams, which is equivalent to one ounce. Seeing as these organisms are so small, microns are used to measure the size of bacteria. The dimensions of bacteria can range from a width of 0.1 to 4.0 microns. The length of bacteria can extend from 0.2 to 50 microns. Being a small organism means that bacteria can have a wide range of habitats. Larger organisms would have difficulty in particular areas. Bacteria does not have this problem and is able to survive the most harsh conditions. Bacteria has been located in upper reaches of the atmosphere, the surface of the ocean, in frozen soil, and on rocks in hot springs. Other types of bacteria contain a endospore that also helps it in extreme conditions. The resting stage, which the endospore protects bacteria and is highly resistant. This does not mean the endospore makes bacteria immortal. Endospores can be eliminated with by boiling them in steam under intense pressure. This is a situation in which bigger is not always better. Bacteria has no ability for thought or intelligence, but has durability and numbers on its side in the fight for survival.
Bacteria has a specific classification. Bacteria cannot be categorized as a plant or animal, due to certain characteristics. Bacteria does have rigid cell walls similar to plants, but uses organic sustenance sources for energy. There are bacteria that get their needed energy from photosynthesis, but this is rare. Bacteria can best be identified by their structural shape. Bacilli are known to have flagella. Those structures allow certain bacteria to be mobile, by propelling it by a whip like mechanism. Bacilli are known to be rod like in shape. Bacilli can have flagella throughout the whole body or just one. Bacilli that originate from spores are resistant to heat, toxic chemicals, and even water. Germinating spores can spread to form newly born bacilli. Cocci are spherical and cluster together.
The size of bacteria is minimal. This however allows it to adapt to other environments more efficiently. Thirty trillion bacteria of standard size can only weigh as much as 28 grams, which is equivalent to one ounce. Seeing as these organisms are so small, microns are used to measure the size of bacteria. The dimensions of bacteria can range from a width of 0.1 to 4.0 microns. The length of bacteria can extend from 0.2 to 50 microns. Being a small organism means that bacteria can have a wide range of habitats. Larger organisms would have difficulty in particular areas. Bacteria does not have this problem and is able to survive the most harsh conditions. Bacteria has been located in upper reaches of the atmosphere, the surface of the ocean, in frozen soil, and on rocks in hot springs. Other types of bacteria contain a endospore that also helps it in extreme conditions. The resting stage, which the endospore protects bacteria and is highly resistant. This does not mean the endospore makes bacteria immortal. Endospores can be eliminated with by boiling them in steam under intense pressure. This is a situation in which bigger is not always better. Bacteria has no ability for thought or intelligence, but has durability and numbers on its side in the fight for survival.
Bacteria has a specific classification. Bacteria cannot be categorized as a plant or animal, due to certain characteristics. Bacteria does have rigid cell walls similar to plants, but uses organic sustenance sources for energy. There are bacteria that get their needed energy from photosynthesis, but this is rare. Bacteria can best be identified by their structural shape. Bacilli are known to have flagella. Those structures allow certain bacteria to be mobile, by propelling it by a whip like mechanism. Bacilli are known to be rod like in shape. Bacilli can have flagella throughout the whole body or just one. Bacilli that originate from spores are resistant to heat, toxic chemicals, and even water. Germinating spores can spread to form newly born bacilli. Cocci are spherical and cluster together.
Cocci can also develop in long chain like structures. An example of this would be the streptococci bacteria. The cocci bacteria can also form almost a structure that looks similar to grapes. Straphylococci can be described in this manner. There is also spirilla , which can be accordion shaped . This type of bacteria would fall under pathogenic spirochetes. Other types of spirilla have a helix structure in appearance. They are not as flexible compared to spirochetes, so they are more dependent on flagella. Their coiled structure can either be regular or irregular in form. There are also other forms that do not fit in these three classifications. Mycoplasms are unique due to the fact they have no form. They are the smallest bacteria known and are referred to as pleuropneumonialike. These organisms have the ability to cause pneumonia. Even though bacteria differs, there are still basic structures that can be found in a majority of bacteria. Bacteria contains cytoplasm, a semipermeable membrane, and ribosomes. The cell wall is very durable. The mesosome is the gateway of the membrane into the cytoplasm. RNA is responsible for forming proteins. DNA within the cell tends to circular.
The only way the structure of bacteria was discovered was by gram staining. This technique was pioneered by bacteriologist Hans Christian Gram in 1884. Using dye or a stain mixed with other chemicals allows for bacteria to be visible in certain colors. Violet colored bacteria are known as gram-positive, while red colored bacteria are called gram-negative. This technique allows physicians to determine which antibiotic to use when combating infection. Gram-positive bacteria are vulnerable to penicillin, while gram-negative bacteria are destroyed by streptomycin. Understanding the anatomy and structure of bacteria gives a biologist a better view of the microscopic world.
Just like any other organism, bacteria and the Monera kingdom have physiological functions. Cyanobacteria, which is blue-green algae falls under the same classification as bacteria. Bacteria and blue-green algae do not contain organelles and are prokaryotic. This means bacteria must receive energy by a variety of methods. Some bacteria require oxygen, which are known as aerobes. There are also bacteria that can not be in oxygen known as obligate anaerobes. There are bacteria that are photosynthesis dependent and are anaaerobic. Sulfur bacteria are not dependent on oxygen , due to the difference in environment. Anaerobes get most of there biological needs through a process of fermentation. This process describes the break down of organic molecules by means of enzymes. Chemosynthetic bacteria require light and nitrogen mixed with sulfur compounds to produce energy. Besides the production of food, bacteria also have to reproduce. The majority reproduce asexually by a method of binary fission. This requires one cell to physically divide into two separate ones. It is possible that some bacteria can divide every twenty minutes, depending on the environment. At this rate a total of 500,000 cells could be produced in about six hours. This quick reproduction explains why disease, decay, the rotting of perishable food, and other chemical processes happen at such a fast rate. Bacteria do not only have binary fusion as a method of reproduction, but a process known as conjugation. This reproduction is sexual rather than asexual and involves two bacteria merging. When they join genes are exchanged. The chromosomes are recombined. Recombination causes a fragment of a chromosome to be transmitted from one bacterium to be added to another. This process of recombination means that bacteria can have a wide range of hereditary attributes. This could be an explanation why certain bacteria are becoming antibiotic resistant. However, this does not mean bacteria is indestructible. High temperature has the ability to eliminate most bacteria species. Non-spore forming bacteria can be killed by disinfectants or boiling water. One of the most important structures to bacteria is plasmids. These structures are small pieces of DNA and carry various genes with no specific purpose. This type of DNA should not be confused with chromosomal DNA. Plasmids may aid in traits that protect bacteria from certain antibiotics. These structures have use in genetic engineering, because they can be manipulated to form recombinant DNA. Another interesting process that bacteria physiologically experience is transduction. Bacteria can exchange chromosomal information when it is infected externally. A virus can infect a bacterium creating a bacteriophage through transduction. The bacterial strain becomes infected, but it is not killed by it. This is an indication of lysogeny, which means a virus cannot be easily detected.
These are the general physiological attributes of bacteria. Even though they are simple organisms, it is possible they are evolving. This should not be a surprise, because other life forms have done it over millions of years.
When bacteria is mentioned there is an association with disease. All bacteria is not harmful, but there are a portion that are linked to lethal illness. The germ theory of disease was developed as early as 1546 by Girolamo Fracastoro. The Italian physician described organisms who carried disease as seminaria. During his time the technology was limited. It was not until the invention of the microscope that humankind could view bacteria. Antoni Van Leeuwenhoek had developed single lens microscopes in 1676. This technological advancement aided in the further study of bacteria and its role in disease. Without the microscope, bacteriology would not exist. Actual classification of bacteria did not occur until the 19th century. Christian Gottifried developed the genus classification of bacterium in 1829. The word is derived from Greek known as bacterion, which means rod like. Bacteria was once placed in a classification with plants. This was incorrect and by the 1960s they were placed as Monerans. Other scientists pioneered the nature of bacteria and techniques for preventing infection. Ignaz Phillip Semmelweiss explored the use disinfectants while working in maternity wards in the 1840s. The Hungarian obstetrician prevented many infections and controlled the rise of puerperal sepsis. The major breakthrough was with Robert Koch in 1876. Koch's examination of anthrax was direct evidence of bacteria's role in disease. Louis Plasteur confirmed this and expounded further on the germ theory of disease. Koch continued to develop techniques to identify which bacteria caused certain infections. The Koch postulates function on these set of rules : bacteria are present in the area of infected tissue, bacteria must be isolated or separated ( pure culture or artificial medium), and other experiments must behave the same way for other animals. That means the inoculation should produce the same results if a particular bacteria is the root cause of infection. Joseph Lester advanced biomedical science from the Koch postulates, by using carbolic acid to fight infections. This resulted in the rise of modern antiseptics. Pasteur continued to develop vaccines, which lead to the rise of immunology. Having a better understanding of bacteria, health, and hygiene resulted in increased life expectancy. Bacteria can still adjust even with various medical techniques. It can be transmitted through the air, water, food, animals, contact with other people, or other objects. There are bacteria that serve important functions for the human body. Natural flora is present in the body. The large intestine requires E. coli to monitor the body's water balance and provide essential vitamins.
The study of bacteria has progressed immensely over the past two centuries. The major focus was mostly on pathogenic bacteria until the 1950s. The study of bacteria allowed for the exploration into other areas related to cells. This includes areas of metabolism, protein synthesis, and molecular genetics. Bacteria's simple structure allows for manipulation, which can reveal much about microbial cells. Bacteriology has also enabled other interdisciplinary studies such as molecular biology and biochemical genetics. Humankind has access to a microscopic world that was unknown. Besides having an impact on the scientific world, bacteria has industrial use. They are essential in the production cheese, yogurt, buttermilk, vinegar, and sauerkraut. Bacteria is also needed in the production of antibiotics streptomycin. Bacteria can also be utilized in the tanning of leather (including hides) and the curing of tobacco. Bacteria, even though it is associated with disease is critical to the life cycle on Earth. Plants and animals require these microorganisms. Bacteria decomposes matter, which happens to organisms when their life cycles end. Nitrogen fixing bacteria form nitrate which green plants use for development. It enables the nitrogen cycle in Earth's ecosystem. Bacteria also has the ability to create fertilizer. The break down of compost heaps made of plant material and soil create a fertilizer through bacteria's ability to decompose organic matter. Bacteria may be small, but is serves an enormous function in Earth's environment.
Further Reading
Barnes-Svarney, Patricia. Science Desk Reference . New York: Stonesong Press Inc, 1995.
"Bacteria." Encyclopedia of Knowledge. Vol. 2. Danbury, CT: Grolier, 1991. 329-32.
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