Bacterial Reproduction and Growth I Growth and Reproduction

Bacterial Reproduction and Growth

I. Growth and Reproduction A. Growth in Living Things 1. Two Ways a) Increase in size of cells b) Increase in number of cells

I. Growth and Reproduction A. Growth in Living Things 2. Microbial Growth -Defined in terms of number of cells, not in cell size a) Binary Fission: asexual reproduction in bacteria 1) Chromosome Duplicates 2) Cell Elongates separating 2 chromosomes 3) Cell Wall grows between chromosomes - No mitotic structures in bacteria (spindles, asters)

I. Growth and Reproduction A. Growth in Living Things 2. Microbial Growth b) Generation Time: interval of time between cell divisions -Staphylococcus aureus 30 minutes -Treponema pallidum 33 hours -Mycobacterium tuberculosis 18 hours -Escherichia coli 20 minutes

I. Growth and Reproduction B. Standard Bacterial Growth Curve -Shows the changes in a population of bacteria over time

I. Growth and Reproduction B. Standard Bacterial Growth Curve 1. Four Phases of Growth a. Lag Phase: no increase in number -Adapting to Environment -Metabolically Active (store nutrients, synthesize enzymes, etc) -Preparing for Binary Fission

I. Growth and Reproduction B. Standard Bacterial Growth Curve 1. Four Phases of Growth b. Logarithmic Phase: exponential growth -number of bacteria double with each Generation Time 1) Limitations for Logarithmic Growth -Nutrient availability -Wastes accumulate -Space/Density -Oxygen Availability (for aerobic bacteria)

I. Growth and Reproduction B. Standard Bacterial Growth Curve 1. Four Phases of Growth c. Stationary Phase: no increase in numbers -Reproductive Rate = Death Rate d. Decline Phase: decrease in number -Environmental conditions limit cell division -Death Rate greater than Reproductive Rate

I. Growth and Reproduction B. Standard Bacterial Growth Curve 2. Four Phases of Bacterial Growth and Human Disease -symptoms appear during Log Phase -bacterial numbers high enough to cause tissue damage

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 1. p. H = "potential of Hydrogen Ion" -Optimum p. H: the p. H at which microorganisms grow best -p. H = 7 for most a. Acidophiles: "acid loving/tolerant bacteria" -p. H 0. 0 to 5. 4 -Lactobacillus: -produces lactic acid -converts milk into buttermilk, sour cream, curds

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 1. p. H = "potential of Hydrogen Ion" b. Neutrophiles -p. H 5. 4 to 8. 5 -most human bacteria that cause human disease c. Alkaliphiles/Alkanophiles -p. H 8. 5 to 12 - Vibrio cholerae (cholera) grows best at p. H=9

Aseptic Techniques: Plate Streaking Read the Aseptic Techniques: Plate Streaking Handout. After completing the reading you will watch a couple of quick videos and complete a check for understanding. After that you will head to the back of the lab and try this technique out for yourself. Be sure to label your plate and draw the T. Pull from the culture tube at your station. We will look at your results next class. http: //www. microeguide. com/lab_skills/ streak_plate. asp

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 2. Temperature a) Psychrophiles - cold-loving organisms -grow best between 0 o. C and 20 o. C -most live in cold water and soil -none in human body b) Mesophiles -grow best between 20 o. C and 40 o. C -most bacteria including human pathogens

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 2. Temperature c) Thermophiles - heat-loving organisms -grow best between 50 o. C and 60 o. C -compost heaps, hot springs, deep sea vents (130 o. C)

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 2. Temperature d) Critical Temperature Ranges -determined by enzyme function 1). Three Critical Temperatures a. Minimum Growth Temperature -lowest temp at which cells can divide b. Maximum Growth Temperature -highest temp at which cells can divide c. Optimum Growth Temperature -temp at which cells divide most rapidly =shortest Generation Time

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 3. Oxygen a) Obligate Aerobic Bacteria - require oxygen to grow 1. Microaerophilic Bacteria - grow best in a low conc. of O 2 ex. UTI, GI Tract bacteria b) Obligate Anaerobic Bacteria - require oxygen free environment to grow -killed by oxygen ex. Clostridium botulinum: - grows in sealed cans of food

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 3. Oxygen c) Facultative Bacteria: (Facultative = not required; optional) -grow in absence or presence of O 2 ex. Staphlococci, Streptococci, E. coli 1. Facultative Aerobes -prefer O 2, but will grow anaerobically 2. Facultative Anaerobes -prefer O 2 -Free, but will grow aerobically

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 4. Moisture -Active cells require water environment -Spores: can exist in dry environments

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 5. Osmotic Pressure = measure of a solution to take up water when in pure water - Higher Concentration of Solutes = Higher Osmotic Pressure

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 5. Osmotic Pressure = measure of a solution to take up water when in pure water a) Cells in Hyperosmotic (Hypertonic) Solutions -Cells lose water and shrink -Plasmolysis: cell membrane separates from cell wall

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 5. Osmotic Pressure = measure of a solution to take up water when in pure water b) Cells in Hypoosmotic (Hypotonic) Solutions -Cells gain water and swell

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 5. Osmotic Pressure = measure of a solution to take up water when in pure water c) Salt as a Preservative -hams, bacon, pickles -high salt exerts high osmotic pressure on cells 1) Halophiles - salt-loving organisms -require salt to survive -found in oceans and other salty bodies of water

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 5. Osmotic Pressure = measure of a solution to take up water when in pure water d) Sugar as a Preservative -jellies and jams -high sugar exerts high osmotic pressure on cells

I. Growth and Reproduction C. Factors Affecting Bacterial Growth 6. Carbon Sources -Carbon needed as energy source and/or building blocks for cell components. a) Autotrophs: Use CO 2 b) Heterotrophs: Use Organic compounds 7. Nitrogen Sources -Needed to synthesize Proteins and Nucleic Acids - From inorganic substances (ex. NO 3 -)