CHAP 4 MICP

• Growth is defined as an orderly and organized increase in all components of an organism
• Microbial Growth is concerned with the increase in the number of cells and not the size of the organism
• A Bacterial Colony is composed of thousands of cells
• Carbon makes up the structural or skeleton backbone of organic molecules
• Heterotrophs are organisms that use organic substances such as sugar or glucose as their carbon source
• Autotrophs are microorganisms that utilize inorganic compounds and inorganic salts as their sole carbon source
• Nitrogen and sulfur are required for the synthesis of proteins
• Nitrogen and phosphorus are essential for the synthesis of nucleic acids and ATP
• Potassium is required for the normal functioning and integrity of ribosomes and participates in certain enzymatic activities in the cell
• Calcium is an important component of the gram-positive cell wall and contributes to the resistance of bacterial endospores against adverse environmental conditions
• Iron is a component of cytochrome, which is part of the electron transport chain and functions as a cofactor for enzymatic activities
• Bacterial cells are composed mainly of water
• Moisture or water serves as a medium through which bacteria acquire their nutrients
• Oxygen is used by aerobic bacteria for cellular respiration and serves as the final electron acceptor
• Aerobes are microorganisms that utilize molecular oxygen for energy production
• Obligate aerobes or strictly aerobes are organisms that strictly require oxygen for growth
• Obligate anaerobes are microbes that cannot survive in the presence of oxygen
• Facultative organisms can grow and survive in both aerobic and anaerobic conditions
• Microaerophiles are organisms that can grow at low oxygen tension, but their rate of growth is diminished
• Thermophiles thrive at temperatures higher than 40 degrees Celsius
• Mesophiles thrive at temperatures between 20-40 degrees Celsius
• Psychrophiles thrive at temperatures between 10-20 degrees Celsius
• pH is the extent of acidity and alkalinity of the environment
• Alkalophiles grow best at a pH of 8.4 – 9.0
• Neutrophiles grow best at a pH of 6.5 – 7.5
• Acidophiles grow best at a pH of less than 6.0
• In human tissue, microbes grow best at a pH of 7.0-7.2
• Halophiles are organisms that require a high salt concentration for growth
• Osmophiles require osmotic pressure for optimal growth
• The Bacterial Growth Curve illustrates the phases of growth of a bacterial population in a fixed cultural volume
• The Lag Phase is the period of adjustment in a new environment, lasting 1-4 hours, with no appreciable increase in the number of microorganisms
• The Log Phase is characterized by rapid cell division and an increased number of bacteria, lasting around 8 hours
• The Stationary Phase is considered a period of equilibrium where the rate of growth slows down, nutrients deplete, and toxins accumulate
• In the Stationary Phase, gram-positive organisms may become gram-negative
• The Death Phase is characterized by rapid cell death where the number of dead cells exceeds the number of living cells, and sporulation continues to occur
• The duration of the Death Phase varies from a few hours to a few days