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One of the most important things to remember about bacteria is their extreme smallness. The fact that they cannot be seen with the unaided eye is one of the chief reasons they are not given the prime consideration they should by people in the dairy and food industries. The average bacterial cell is 1/25,000 of an inch in length and even smaller in diameter. In other words, one could place 25,000 bacteria cells, side by side, on an inch-long line. By contrast, if 25,000 people were lined up shoulder to shoulder, they would make a line over 18 miles long. For us to see these incredibly small living things, a microscope with a magnification of over 800 power or more is needed. In contrast, most binoculars used to observe sporting evens magnify objects about 7 to 10 power. So if these bacteria are too small to see with the eye, how does one know they are present in a food? The process we use is to plate the food being examined to determine if bacteria are present. One takes a sample of food being examined and places a small portion of it on an agar that contains food on which bacteria will grow. The agar, a gelatin-like substance containing the bacterial food, is actually placed in a Petri plate, a shallow round dish with a cover. A small portion of the food being examined is spread over the surface of the agar. The amount of food being "plated" depending on the suspected number of bacteria in the food. For foods containing only a few bacteria, up to one gram (g) or milliliter (mL) will be "plated". For foods heavily contaminated with bacteria, one-millionth or a gram or mL of the food would be plated. The food is diluted with sterile water to achieve this small amount on the agar in the Petri plate. If bacteria are present they grow rapidly producing offspring that within 12 to 48 hours will produce a "mound" of bacteria in one spot. We can see this mound and call it a colony. The assumption is that each colony originated from one bacterial cell 12 to 36 hours ago. If this assumption is true--sometimes it is not-likely one can calculate the number of bacteria in the original food placed on the agar in the Petri dish by knowing how much food was placed on the plate originally. An individual bacterium is very tiny. They are usually one or two micrometers across. Since micro means 1/000,000 (one-millionth), they are commonly one millionth of a meter in diameter. A meter is 39.37 inches (3.33 inches longer than a yard). How many bacteria lying snugly side-by-side would it take to reach one meter? Since they are one to two micrometers wide, it would take about one million lying side by side to reach one meter, or 500,000 if they were 2 micrometers wide. Is bacteria the same thing as a virus? Bacteria are very small one-celled organisms. There are many different kinds & they live all around us on your computer keyboard, on the table, on your face, and in your body! Most of them are not harmful. Some, however, can cause illness in our bodies. If you get sick from bacteria, your doctor may prescribe antibiotics, a medicine made from fungus, a natural enemy of bacteria, to kill the bacterial infection. Viruses are much smaller and are unlike any other living thing on earth. In fact, scientists disagree as to whether viruses are living at all. When a tiny virus comes into contact with the type of cell that it likes to attack, the virus sticks to the cell & injects it with instructions. These instructions replace the natural instructions in the cells nucleus. The cell gets confused and begins to follow the new (wrong) instructions, and uses its energy to make more viruses instead of what it was doing before. When the cell is full of new viruses, it explodes & the viruses float off to find more cells. Our immune system makes white blood cells that kill viruses, but sometimes it takes time. Once your white blood cells figure out how to kill the virus, they never forget. If that type of virus ever attacks your body again, your white blood cells will kill it instantly. Bacteria are very small. They do big things. If a three micron long bacterium were enlarged to the size of a six-foot, tall person, and then the person was enlarged the same way, the person would be about 700 miles tall. Yes, bacteria are small. Bacteria often live in tunnels left behind as hyphae of soil fungi die. Amoebae are not able to attack the bacteria in the minute- diameter tunnels (SHIGO, 1999). While some bacteria are small spheres, others are shaped like tiny hotdogs (frankfurters, or sausages). Some species of bacteria hang together in chains like a chain of sausages. Often these chains contain only a few cells, but some form chains of hundreds of cells. The hotdog shaped bacteria are usually 2 or 3 times as long as wide, but some are very long in comparison to width. Some individual cells are long shaped like a needle. Many species of bacteria reproduce by a wall forming across the cell dividing the orginal cell into two daughter cells having the same shape and genetic composition. Since the cells are growing, by the time division (fission) is completed each of the daughters may be as large as the mother cell was before it began fission (splitting). Bacteria are very small (microscopic) unicellular procaryotes, mostly without chlorophyll. (All other organisms are eucaryotic -- having DNA surrounded by a nuclear membrane. With the exception of few very interesting photosynthetic bacteria and others that are chemosynthetic, bacteria are poor synthesizers. Most are saprophytic heterotrops (obtaining nourishment from dead organic material) and are valuable decomposers in soil and water; but of course, some decomposers of food and plant fibers are pests and a few species cause very serious animal and plant diseases. To familiarize yourself with the three types of bacteria, look first at the stained slide of the "type bacteria". The cocci (singular: coccus) are spherical, the bacilli (singular: bacillus) are rod-shaped, the spirilli (spirillum) are spiral-shaped. Sometimes the cells are single, sometimes they are joined together in chains or groups. For instance, cocci in chains are streptococci, in pairs: diplococci, in irregular groups: staphylococci, in regular cubes: Bacteria are very small living organisms made of only one cell . They are present just about everywhere : the air, the soil, and the skin, for example. Many of them are microbes that cause diseases (rhinitis, listeriosis, and others), but others are very helpful to humans. For example, bacteria in the intestine help digestion and we often use bacteria to make food products (yoghurt, sauerkraut, and others). Bacteria are very small, single-celled living things. Their cell walls differ from those of other living things they are made from a different material and the nuclei and organelles are not enclosed in membranes. Bacteria are very successfully adapted to an immense range of habitats. While most need oxygen for respiration, others use sulphate and nitrates instead of oxygen. Bacteria are very small micro organisms that can not be seen with a naked eye. So we can not see them swimming in water. The other problem is that often millions of bacteria are condensed in a small spot. To see bacteria, you grow them in a nutrient agar plate so each bacteria will become a colony of thousands of bacteria. Then we can see them as a bacteria colony. Bacteria are very small - they cannot be detected by the naked eye - up to 3 million can fit on the end of a pin. Some bacteria are essential to life and are naturally present in the human gut and help in the digestion of food. Bacteria which are harmful to man are called Pathogens and it is these that cause food poisoning and other illnesses. Many of these bacteria are destroyed during cooking, however some of them may produce spores and toxins which can survive very high temperatures, and are therefore able to re-contaminate food as it cools. As an aside not all bacteria are very small i.e a few microns, there are some species that are fractions of a millimetre in diameter. The largest found to date, a bacterium 0.75mm across, was recently reported in the press and is thus just visible to the naked eye. The full illustrated paper on this bacterium is in the April 16th 1999 edition of the magazine 'Science'. Bacteria are very small, yet they show a surprising degree of complexity in their structures. Bacteria causing disease (pathogens) have various properties that make them have a better ability to create illnesses. One important property is the ability to attach to the victim. Many bacteria are capable of movement in their environment by gliding motility. Bacteria have a long, flexible, spiral shaped structure, the flagellum, that helps to push the microbe through solution. As a microbe grows, it has to synthesize most of its self. Bacteria are very small creatures that can only be seen with a microscope. Bacteria are very small (<1 to 5 microns) and can only be seen adequately by electron microscopy. Fungi and protozoa are much larger (12 to 200 microns or even larger) and can be seen with a light microsope at x 400 magnification. Bacteria multiply by splitting into halves, a process called binary fission. Under the most favorable conditions one bacterial cell will divide into two cells in about 20 to 30 minutes. Twenty minutes later, these two cells will elongate and split into four cells. Then after 20 more minutes, each of the four cells will divide into eight cells and so on. It's called a logarithmic progression ("log growth", as the bacteriologist call it). For example, 1 cell 2 cells 4 cells 8 cells 16 cells 32 cells 64 cells 128 cells 256 cells 512 cells 1024 cells, etc. In the previous examples one bacterial cell, multiplying about every 20 minutes, increases it's number in less than 3 hours to around 1020 cells. In 36 hours of continuous, unrestricted growth, there would be enough bacteria to fill 200 five-ton trucks! Obviously, bacteria do not multiply indefinitely, so what does control bacterial growth? One factor is temperature. Nanobacteria have exceptional properties. Firstly, nanobacteria can be cultured in cell culture media for mammalian cells. However this organism does not need mammalian cells at all. It grows under conditions similar or identical to those used for mammalian cells. Doubling time is surprisingly similar to the human fibroblasts - three days. The bacteria are very small, coccoid, and the average population size is around 0,2-0,3 micrometer in diameter. Since they are so small we can not use light microscopy to observe them. However, they have a unique property. They broduce biogenic apatite in the form of a thick shell, and as a result they become extremely easily visible. Apatite is a high-density material and can be visualized easily. They appear to have extremely thick cell walls yet they are filterable in relatively high yields through 0,2 micrometer filters and some of them will pass through 0,1 micrometer filter. Heat resistance is exceptional. They endure 90oC for 1 hour. So this is the first heat resistant organism or thermophilic organism isolated from humans. We can not say it is really thermophilic in the classical sense but at least it endures temporal heat treatments. It can grow excellently at 45oC. Since we use culture media containig a serum, it is not possible to go to higher temperatures because we will cook the medium. In addition, the organism is highly resistant to gamma irradiation. This is a unique phenomenon. It is also resistant to antibiotics like aminoclycosides, although high doses definitely are effective against them. They are extremely resistant to disinfection and lysis. Bacteria are very small single-celled microorganisms that reproduce by cell division. Bacteria are very small single celled organisms that are found everywhere iin the environment and normally live in harmony with the body. Some specific types of bacterial infection have their own name eg Stangles but most infections are non specific and happen after an accident or weakening of the immune system. Bacteria are important organisms in disease and our ecosystem.Bacteria are very small, measuring about 0.1 to 20 micrometres. There are two distinct groups f bacteria:the Gram-positive and the Gram-negative. They differ in their cell walll composition and the way they cause disease.The Gram-negative bacteria normallly secrete toxins,poisonous substances which destroy cells. Bacteria can also be grouped according to their shape:straight rods, round coccus or curved spirochetes or comma-shaped vibrios. Most bacteria have a cell wall, but unlike other cells, their genetic material is not enclosed by a nucleus. Bacteria can be helpful to us by fixing nitrogen and breaking down dead plants and animals back into the ecosystem. Some bacteria can survive in adverse enviroments by forming spores.Some bacteria have a tail known as flagella which beats around to move the bacteria forward .
What Is Microbiology?
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