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Factors affecting the growth of microbes


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Factors affecting the growth of microbes

  2. 2. In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH very close to 7. pH measurements are important in medicine, biology, chemistry, agriculture, forestry, food science, environmental science ,oceanography, civil engineering, chemical engineering, nutrition, water treatment & water purification, and many other applications. PH(ACIDITY AND ALKALINITY
  3. 3. Most bacteria grow best around neutral pH values (6.5 - 7.0) Some bacteria thrive in very acid conditions and some can even tolerate a pH as low as 1.0. Such acid loving microbes are called acidophiles. Even though they can live in very acid environments, their internal pH is much closer to neutral values. Human blood has a normal pH of about 7.41. The pH of urine has a wider range. Normal ranges for urine pH are from 4.5 to 8.
  4. 4. Most spoilage bacteria grow best near neutral pH Acidity and alkalinity levels can also influence microbe growth. Most microbes grow at a more neutral pH range between 6.5 and 7.5. Some microbes can grow outside that pH range. Yeast and moulds have much greater tolerance to acidic (lower) pH The optimum pH range is usually quite narrow so that small changes in the pH can have large effects on the growth rate of the organism
  5. 5. Acidophiles Neutrophiles Alkaliphile
  6. 6. Thiobacillus acidophilus is an example of a thermo-acidophile, meaning a bacterium that likes both extremely hot and extremely acidic environments. It is found in acidic geyser basins in Yellowstone National Park, as well as other places. Acetobacter aceti has modified its proteins so that they aren’t harmed by acidic environments. A study in applied environmental microbiology found more than 50 specialized proteins that had evolved to help the bacterium deal with acidic conditions Helicobacter pylori is the most common chronic bacterial infection in humans. Although most people who have the infection have no symptoms or problems with it, it can cause chronic gastritis, most peptic ulcers, and gastric adenocarcinoma and gastric lymphoma. Thiobacillus acidophilus Acetobacter aceti Helicobacter pylori any organism that lives and thrives in an alkaline environment, such as a soda lake
  7. 7. Vibrio cholerae is a Gram-negative, comma-shaped bacterium. Some strains of V. cholerae cause the disease cholera. V. cholerae is a facultative anaerobic organism and has a flagellum one cell pole. microalgae are microscopic algae, typically found in freshwater and marine systems. They are unicellular species which exist individually, or in chains or groups. Vibrio cholerae microalgae any organism that thrives in a relatively neutral pH
  8. 8. Natronomonas pharaonis was isolated from soda lakes where it has to cope with two extreme conditions, high salt concentrations and an alkaline pH of 11. It grows optimally in 3.5 M NaCl and at pH 8.5 Natronomonas pharaonis any organism that lives and thrives in an alkaline environment, such as a soda lake; a form of extremophile
  9. 9. Oxygen is a natural element essential to all human life on Earth, as well as the lives of other air-breathing mammals. But there are some living things on Earth, including some organisms, that consider oxygen to be the enemy. While some forms of bacteria need some oxygen to grow, others cannot grow if oxygen is present. AEROBIC -aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. ANAEROBIC - anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present.
  10. 10. obligate aerobe- is an organism that requires oxygen to grow. facultative anaerobe- is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent. microaerophile - is a microorganism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere. Mycobacterium tuberculosis Saccharomyces cerevisiae Campylobacter
  11. 11. Obligate anaerobes- are microorganisms that are killed by normal atmospheric concentrations of oxygen : Aerotolerant organisms- considered an anaerobe since it does not use oxygen to oxidize molecules during energy production. Prevotella spp