chapter 5 bacte

• Metabolism is defined as the sum of all chemical processes that take place in a living organism and results in its growth, energy generation, waste disposal, and other functions in relation to cell nutrient distribution.
• Bacterial metabolism is divided into two major parts: anabolism or the constructive phase and catabolism or the destructive phase.
• In anabolism, there is a synthesis of complex molecules and energy production; whereas in catabolism, the large complex molecules are broken down into simpler, smaller molecules accompanied by energy utilization.
• Bacterial metabolism consists of biochemical reactions that break down organic compounds and produce new bacterial structures from the resulting carbon skeleton.
• All biochemical reactions in the cell depend on the presence and activity of specific enzymes.
• Energy Production is accomplished by the breakdown of chemical substrates through the degradative process of catabolism that is coupled with oxidation-reduction reactions.
• Compounds, such as glucose that have many hydrogen atoms, are highly reduced compounds, and thus contain a large amount of potential energy.
• Glucose is an essential nutrient for energy production in organisms.
• To produce energy from glucose, microorganisms use two general processes, inspiration and fermentation.
• Respiration is an efficient ATP-generating process in which molecules are oxidized and results in an inorganic molecule as the final electron acceptor.
• In respiration, glucose is completely broken down and results in a high-energy production.
• In the presence of oxygen, glucose is changed into carbon dioxide and water.
• Respiration is carried out by obligate aerobes and facultative anaerobes.
• In an aerobic respiration, oxygen is the final electron acceptor, while in anaerobic respiration, one of the exogenous substances, such as nitrate, sulfate, and fumarate, is the final electron acceptor.
• Glycolysis (Embden-Meyerhof-Parnas pathway) is the first stage in carbohydrate metabolism.
• Glycolysis is the oxidation of glucose to pyruvic acid and is the major route of glucose metabolism in most cells.
• Some bacteria that undergo mixed acid fermentation are Enterobacter, Serratia, Erwinia, and Bacillus.
• Homolactic Fermentation involves the reduction of pyruvate to lactate (for Streptococcus and Lactobacillus), which is used to make yogurt, sauerkraut, and pickles; it means that only one acid is produced after fermentation.
• Krebs Cycle (Tricarboxylic Acid or TCA cycle) is the most important process for the complete oxidation of a substrate under aerobic conditions.
• Fermentation forms a mixture of end products (lactate, butyrate, ethanol, and acetoin) in the medium; the analysis of these products is useful for the identification of anaerobic bacteria.
• Fermentation releases energy from sugars or other organic molecules, such as amino acids and purines.
• The substrate for the Krebs Cycle is the acetyl coenzyme A.
• Fermentation does not require oxygen (anaerobic process), the use of Krebs cycle, or an electron transport chain.
• Butyric acid fermentation utilizes formic hydrogenlyase that converts formic acid into an equal amount of hydrogen and carbon dioxide for the biosynthesis of new cell components; for the maintenance of the physical and chemical integrity of the cell; for the activity of the locomotor organelles; for the transport of solutes across membranes; and for heat production.
• Some bacteria exhibiting butanediol fermentation are Clostridium, Pusobacterium, and Eubacterium (obligate anaerobes).
• Heterolactic Fermentation produces substances other than lactate, such as alcohol, carbon dioxide, formic acid, and acetic acid.
• In the Krebs Cycle, an enzyme system converts pyruvate into carbon dioxide and an acid.
• Butyric acid fermentation involves the production of ethanol and acids, such as lactic, acetic, succinic, and formic acid.
• Alcoholic Fermentation turns sugar into ethanol and carbon dioxide (for fungi, algae, protozoa, and some bacteria).
• Butanediol fermentation involves the conversion of pyruvate into butyric acid along with acetic acid, carbon dioxide, and hydrogen.
• Mixed acid fermentation involves the conversion of pyruvate into acetoin then reduced to 2,3-butanediol with NADH; small amounts of ethanol and mixed acids are also synthesized.
• Once energy is obtained, bacteria, as well as other organisms, utilize it in various ways.
• Fermentation is carried out by both obligate and facultative anaerobes.