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Bacteria are found almost everywhere on Earth, including in the seas and lakes, on all continents (including Antarctica), in the soil, and in tissues of plants and animals. Reproduction: Bacteria grow in colonies and reproduce rapidly by asexual budding or fission, in which the cell increases in size and then splits in two. Bacteria can also undergo conjugation in which two separate bacteria exchange pieces of DNA. Resting Stages: Under unfavorable environmental conditions, bacteria develop a thick outer wall and enter a dormant phase - in this resting state, the bacterium is called a spore. The bacteria can remain in this dormant state for long periods of time, surviving conditions that kill many other organisms. Effects of Bacteria: Although bacteria case many illnesses (including dental caries, strep throat, cholera, and tuberculosis) and cause the harmful "red tide" seen in many lakes, bacteria also have many positive effects, including releasing nitrogen to plants and decomposing organic material. Bacteria also have crucial roles in the fermentation process and the manufacture of cheese and yogurt. Bacteria Deep in the Oceans: Bacteria have recently been found living deep in ocean canyons and trenches that are more than 32,800 feet (10,000 meters) deep. These bacteria live in total darkness by thermal vents at tremendous pressure. These bacteria make their own food (via chemosynthesis) by oxidizing sulfur that oozes from deep inside the Earth. Where do bacteria come from? * People - People commonly carry food poisoning bacteria on their skin and also within the nose, mouth, ears and intestines. These bacteria may contaminate food directly by touch or by food handlers sneezing and coughing. * Raw Food - A variety of raw food, particularly poultry, red meat and uncooked shellfish may carry food poisoning bacteria. Unwashed salad products may also carry bacteria. * Pests - Many insect pests, notably flies, wasps and cockroaches, carry food poisoning on their legs and bodies. They contaminate food and work surfaces when they walk on them. Many rodents commonly excrete bacteria and may contaminate worktops and food. * Dirt/Dust - Food poisoning bacteria may be present in dirt and dust. It is for this reason that thorough cleaning is vital. Various species of bacteria thrive on different food sources and in different microenvironments. In general, bacteria are more competitive when labile (easy-to-metabolize) substrates are present. This includes fresh, young plant residue and the compounds found near living roots. Bacteria are especially concentrated in the rhizosphere, the narrow region next to and in the root. There is evidence that plants produce certain types of root exudates to encourage the growth of protective bacteria. Bacteria alter the soil environment to the extent that the soil environment will favor certain plant communities over others. Before plants can become established on fresh sediments, the bacterial community must establish first, starting with photosynthetic bacteria. These fix atmospheric nitrogen and carbon, produce organic matter, and immobilize enough nitrogen and other nutrients to initiate nitrogen cycling processes in the young soil. Then, early successional plant species can grow. As the plant community is established, different types of organic matter enter the soil and change the type of food available to bacteria. In turn, the altered bacterial community changes soil structure and the environment for plants. Some researchers think it may be possible to control the plant species in a place by managing the soil bacteria community. 1. Most species of bacteria are identified by their metabolic actions, which are determined by how they respond when grown on different growth media. 2. Prokaryotes differ from eukaryotes by (1) multicellularity - bacteria are not multicellular; (2) cell size - bacteria are very small; (3) chromosomes - bacteria lack a nucleus and DNA is not complexed with proteins; (4) cell division and genetic recombination - bacteria do not have true sexual reproduction, but do have means to transfer genetic material; (5) internal compartmentalization – bacteria lack membrane-bound organelles; (6) flagella - bacterial flagella are composed of single fibers of flagellin; (7) autotrophic diversity - bacteria have several different kinds of aerobic and anaerobic photosynthesis with a variety of end products including sulfur, sulfates, and oxygen; other bacteria are chemosynthesizers, metabolizing various inorganic and organic compounds. 3. The bacterial cell wall is a network of polysaccharide molecules cross-linked by polypeptides. Gram-positive bacteria have a plain polypeptide-linked polysaccharide wall, whereas gram-negative bacteria have an additional layer of large lipopolysaccharide molecules deposited over a plain layer. Gram-negative bacteria are generally more resistant to most antibiotics because of the nature of the cell wall. 4. Archaebacteria differ from the Eubacteria in a number of ways, most notably in the rRNA base sequences, the absence of muramic acid in their cell walls, and their often extreme habitats (anaerobic, very salty, very hot, etc.). Their unique metabolism allows them to synthesize methane from carbon dioxide and hydrogen, generating energy along the way. Researchers have found tiny critters that could live in environments like Mars. No, they are not Martians! They are a type of bacteria that lives here on Earth. These bacteria are very small, so they are called microorganisms or microbes. They are relatives of the first life on Earth. Today they live in places where there is no oxygen like swamps, sewage and even in our guts. To see whether these bacteria would be able to survive in a Martian environment, researchers put them into a chamber where the pressure could be reduced to be like the conditions on Mars. Despite the different environment, the little critters survived and grew! Life like this may exist today below the surface of Mars where an underground ocean of ice sits. Or, creatures like these might have lived on Mars in the past! Most bacterial diseases will clear up by themselves as the body gradually kills off the invading bacteria but the process of recovery is speeded up by the use of Antibiotics which are chemicals that were discovered to effectively kill off bacteria. Bacteria however do often learn how to defend themselves against antibiotics and develop ‘resistance’. Antibiotics do however have disadvantages in that they kill off good as well as bad bacteria. This means that for example on the skin an antibiotic cream will make the skin weaker because it kills off all the good bacteria that are helping the skin work properly. The same is true of taking antibiotics by mouth – the antibiotics kill off all the beneficial bacteria in your intestines before they manage to get to the site of an infection in the body. This is whey many vets advise taking probiotics – to replace the good bacteria that have been killed off. Bacteria like different temperatures for growth. The largest and most common group is called mesophilic (mess-o-fill'-ik). These bacteria are somewhat like people in that they prefer moderate temperatures for growth. With this group the "best"--that is, the most rapid growth is around 70 to 98 degrees. The precise "best" growth does vary with the species of bacteria. The mesophiles can also grow down to 45 degrees and up to 110 degrees, but do so more slowly. In the bacterial world, some like it hot! These bacteria live and multiply best at approximately 130 degrees F. but can grow anywhere between 110 and 190 degrees F. They are referred to as the thermophilic (ther-mo-fill'-ik) group. Contrary to the belief of some people, cold or freezing does not always kill bacteria. In most cases it just stops or slows down their growth. Extended freezing, however, will slowly kill them. Psychrophilic (sigh-crow-fill'-ik) bacteria will grow from 32 to 90 degrees F. with most having their "best" growth around 50 to 70 degrees. Because they grow better NOT best than the mesophilic bacteria at refrigerated temperatures--32 to 45 degrees--, this group is most often responsible for spoilage in refrigerated foods. So how does one control bacterial growth with temperature. If you have a food that is given a "light" heat treatment, like pasteurization, the food must be kept cold so that the growth of any spoilage bacteria surviving the pasteurization process is slowed. (The pasteurization process is designed to kill all pathogens, but not all spoilage bacteria). Obviously cold storage does not stop all bacterial growth since spoilage does eventually occur. But the colder you store the product the longer it will take for the spoilage bacteria to grow and spoil the food. In the dairy and perishable food industries we say, "Life begins at 40"--(degrees, that is). Keep the food at 40 or less and you will get the shelf life you need with a properly processed food. There are other ways that one can control the growth of bacteria. Bacteria need water to grow and even though some of them have the ability to resist long drying out periods, keeping things dry will stop growth and in some instances will kill them. Therefore, it is a good policy to keep utensils and some equipment dry when not in use. Remember, too, that the bacteria responsible for spoilage of foods (mesophilic and psychrophiles) can be killed by hot water. Ten minutes at 150 degrees F. will be sufficient. And, germicides such as chlorine and quaternary ammonium compounds are also effective. Bacteria must eat. And milkstone, which is a dried milk-mineral deposit, and other mineral deposits are good food sources. Therefore, it is necessary to keep all equipment that comes in contact with the food scrupulously cleaned, and sanitized. Likewise the environment in which the food is processed also must be kept cleaned and sanitized. Bacteria from the environment can be "transported" to the food processing areas on hands, feet, clothing and by other unclean equipment. Bacteria can even "float" in on air currents and splashing water can dislodge bacteria from surfaces and make them airborne. These airborne bacteria can eventually contaminate cleaned surfaces. Bacteria are the most abundant of the soil organisms (>100 million per gram or teaspoon of soil) and the most important within the top 6 inches of soil. Bacteria are very small single-celled microorganisms that reproduce by cell division. Great diversity exists among bacteria: some species are aerobic, some anaerobic, some autotrophs and some heterotrophs. Compared to cultivated agricultural soils, bacteria populations are generally greater in grassland soils because of higher root densities, available nutrients and organic matter content. Like many soil organisms, bacteria are influenced by soil temperature, water content and pH. Soil bacteria populations, therefore, fluctuate with the season, with largest populations in the spring, early summer and fall. Due to a quick generation time (as fast as 20 minutes between cell divisions), bacteria can quickly colonize and exploit organic materials once conditions become favorable for growth. Bacteria are responsible for many key biological reactions such as nitrogen fixation and sulfur oxidation, which make these nutrients available to plants. Also, bacteria are instrumental in the breakdown of cellulose and other structural components of thatch. In turfgrasses, heterotrophic bacteria are responsible for decomposition of organic materials and regulation of soil organic matter. However, not all bacteria are beneficial; some are pathogenic to plants and animals. The only known bacterial problem in turfgrass is C-5 Decline of Toronto creeping bentgrass. However, other bacteria species are being investigated as biological control agents for weeds (Xanthomonas campestris pathovar poannua), insects (Bacillus popillae and B. thuringensis) and nematodes (Beauvaria bassiana and Pasteuria sp.). Aerobic metabolism didn't appear overnight, but evolved gradually over several billion years as primitive fermentative cells adapted to the exhaustion of raw materials, and the appearance of oxygen in the earth's atmosphere. Oxygen was the world's greatest ecological disaster. It is an immensely toxic gas, that readily generates free radicals which damage sensitive biological molecules. Even today, our bodies depend on delicate control mechanisms to deliver oxygen to our tissues in carefully regulated amounts. When free oxygen first appeared in the atmosphere, millions of primitive species either became extinct, or were confined to anaerobic niches where they were protected from its harmful effects. This new threat was created by the blue-green algae, and subsequently by the green plants. These photosynthetic organisms progressively oxidised the earth's crust around two billion years ago. Bacteria were the first group to deal with this problem. Over hundreds of millions of years, as more and more powerful oxidants appeared in the biosphere, bacteria gradually evolved the respiratory chain, starting from NAD and NADPH at the reducing end, and creating new enzyme systems one by one until finally they could handle molecular oxygen: the ultimate killer molecule. Our kind of cells were a bit slower off the mark. Our distant ancestors probably ate bacteria for a living. They were phagocytic cells that swallowed and digested bacteria in cytosolic vacuoles, just like our macrophages do today. Eventually some of these predators formed symbiotic partnerships with their prey, and eukaryotic cell lines were created. These were hugely successful team efforts. Our bacterial endosymbionts evolved into mitochondria that dealt with oxygen efficiently and manufactured ATP, while the larger host cell provided the physical bulk and swallowing capacity that bacteria could never emulate. The detailed structure of eukaryotic cells still reflects their distant evolutionary origin. Each mitochondrion is still wrapped in its own membranous bag. In addition to the vital electron transport chain, mitochondria still have bacterial-type ribosomes for making proteins, and their own DNA in their own circular bacterial-type chromosome. These structures, however, are a pale shadows of their former selves. Most of the mitochondrial genome has been taken over by the cell nucleus, and mitochondria today are utterly dependent on manufactured proteins and lipids imported from the cytosol. Energy metabolism is subject to ceaseless selection pressure. If you can swim 1% faster or further than the competition, then your progeny will inherit the earth, at least until something better comes along. If you examine the fine details of our energy-yielding pathways, then you find that every possible opportunity has been taken to increase the efficiency of the process, and to maximise the delivery of ATP. We have also evolved pollution control systems that minimise the production of toxic by-products. The parallels between the molecular motors in living organisms, and the mechanical systems in modern vehicles are remarkable, although the components differ ten million times in size. Among the cellular machinery we can already identify emission control systems, fuel pumps, heaters, batteries, turbines, electric motors, drive shafts, gearboxes and universal joints. The major difference is that the cellular systems are self-maintaining and achieve performance levels that Ferrari can only dream of. Truly, we can speak of "supercharged cells". In the very limited time available I can only provide a few selected examples. Rest assured that the remainder of this equipment is just as polished, and there will be many opportunities to study it in detail during your university course.
What Is Microbiology?
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