formal lab report bisc 300.docx - Vida Andoun Prof Dr...

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Vida Andoun Prof. Dr Birjandi BISC 300, Formal lab report 5 October 2018 Nutrition and growth of bacteria Abstract Bacteria requirements for growth are source of energy, organic carbon source like sugars and fatty acids and metal ions such as iron. Also, some other factors that have effects on bacterial nutrition and growth are temperature, pH, osmolarity, pressure and oxygen. At this experiment we conducted two different methods for measurement of bacterial nutrition, growth of microorganisms in various media in indirect measurement by using spectrophotometer and every 30 minutes measured the absorbance of each. Then in direct method performed serial dilution from 10 -1 (0.5 mL of the original culture into 4.5 mL of sterile saline) through 10 -8 . Then, placed cultures of 10 -5 , 10 -6 , and 10 -7 into each agar plates. Another method was using of selective and differential. For each different phylum we had growth at specific plate. For example, at Eosin Methylene blue (EMB) only gram-negative bacteria can grow such as E.coli, for Mannitol Salt agar we had growth of Staphylococcus aureus and for the Shigella sonnei and Salmonella enteritidis grew at the Hektoen Enteric (HE) agar plate Introduction Bacteria are some of the most diverse groups of macroscopic, single-celled organisms. They are in almost every environment, from the bottom of oceans to below the earth’s surface to the GI tract of human. They are called prokaryotes due lack to lack of nucleus and organelles.   Three basic shapes of bacteria are spheres (Cocci), rods (Bacilli), and spirals. The bacterial cell contains water (about 80% of total weight), proteins, polysaccharides, lipids, nucleic acids, and mucopeptides. Bacteria’s minimum nutritional requirements is water, a source of carbon, a source of nitrogen, and inorganic salts. So, bacteria are classified based on their nutrition and energy requirements and their ability to synthesize specific metabolites. In fact, all the organisms are classified into two categories, autotrophs or carbon source for those that are self-feeders make their own food by using atmospheric carbon dioxide and nitrogen that make them independent existence in water and soil, heterotrophs or other-feeders are those use ready-made organic molecules for food that are not able to synthesize their own 1
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metabolites and dependent on organic compounds. There are two branches under each category, for autotrophs there are photoautotrophs, using light as the energy source such as photosynthetic bacteria (green sulfur, purple sulfur, and cyanobacteria). Chemoautotrophs are those that use inorganic compound as the energy source such as iron, sulfur, hydrogen, and nitrifying bacteria. The branches for heterotrophs are photoheterotrophs that light is their source of energy like purple nonsulfur bacteria and green nonsulfur bacteria, and chemoheterotrophs use organic compounds as their source of energy that most bacteria are among this branch of the heterotroph category and chemoheterotrophs differ in the amount and type of organic compounds they consume. Also, some bacteria require specific organic compounds in very small quantity that are
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