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GROWTH OF MICROORGANISMS
Nutritional Classification Based upon energy and carbon sources Energy source- electron donors –Phototrophs (light nourishment) –Photosynthesis
Electron Donors Chemotrophs Oxidation Reduction Breaking & forming bonds
Carbon Source Autotrophs (self) Heterotrophs ( different) Combination of terms
Photoautotrophs Energy(electrons) source-light Carbon source-CO 2 Green & purple Sulfur bacteria
Photoheterotrophs Energy source-light Carbon source –organic cpds Green & purple non Sulfur bacteria
Chemoautotrophs Energy source is oxidation -reduction reactions Carbon source Nitrifying bacteria
Chemoheterotrophs Energy & carbon source Remove electrons from H in organic cpds Final electron acceptor is oxygen Final electron acceptor is organic cpd
Physical Requirements for Growth Temperature-range –Psychrophiles –Psychrotrophs
Temperature Mesophiles-25-40C Thermophiles-50-60C Hyperthermophiles
Determination of Range Maximum temperature Minimum temperature Optimum temperature is closer to max
pH Measures acidity or alkalinity Bacteria grow best at slightly alkaline pH Add buffers to bacterial cultures Molds & yeasts lower pH
Osmotic Pressure Microbes need water to grow Use salt/sugar to preserve food Obligate halophiles Facultative halophiles
Chemical Requirements for Growth Carbon source-50% of dry weight of cell Nitrogen source-amino acids, nucleic acids
Minerals Trace elements –Small amounts of Fe, Zn, Cu, Co etc. –Macronutrients-S & P Water-medium for chemical reactions
Other Growth Requirements Growth factors-essential nutrients E. coli needs no growth factors
Other Growth Requirements Buffers A solidifying agent
Agar Advantages Few organisms degrade it Liquefies at 100 C Liquid until 40-50 C Lab-keep liquid at 50 C Once solidified, heat to 100 C Gelatin –Nutrient for some organisms –Liquefies at 35-37 C
Oxygen Requirements Aerobes –Use molecular oxygen for respiration –Superoxide free radicals (O. - ) –Superoxide dismutase- must have –H 2 O 2 is toxic
Oxygen Requirements Facultative anaerobes
Oxygen Requirements Obligate anaerobes
Oxygen Requirements Aerotolerants Microaerophiles
Growth of Bacterial Population Binary fission or budding Generation time-doubling time
Growth Curve Lag phase-preparing to grow Log phase Stationary phase-growth ceases Death Phase
Growth of a Colony Mass of cells –pure culture Some colonies are distinct Mixture of cells in different phases of growth
Growth of a Colony Location within colony determines access to oxygen Surface cells fully aerobic E. coli obtain energy aerobic respiration Embedded cells in center-anaerobic
Biofilms In nature, microbes in liquid environment Cells imbedded in extracellular slime –Excreted by cells Type of defense mechanism
Biofilms Quorum sensing Important role in infections Soaps & disinfectants
Microbial Nutrition Cell metabolism
ELEMENTS OF MICROBIAL NUTRITION, ECOLOGY, & GROWTH
Chapter 6 Microbial growth. Microbial growth – increase in the number of cells Depends on environmental factor such as temperature. Divided into groups.
Microbial Growth For microorganisms, growth is measured by increase in cell number, due to their limited increase in cell size.
Microbial Growth pp Cell wall Partially formed cross wall DNA (nuclear area) Fig Part B 1.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology.
General Microbiology (Micr300) Lecture 4 Nutrition and Growth (Text Chapters: ; 6.1; ; )
Chapter 6, part A Microbial Growth.
Microbial Growth Chapter 6.
Microbial Growth. What do they need to grow? Physical needs –Temperature, proper pH, etc. Chemical needs –Molecules for food, ATP production, coenzymes,
Bacterial growth Assist. Prof. Emrah Ruh NEU Faculty of Medicine
Microbial Growth. Growth of Microbes Increase in number of cells, not cell size One cell becomes colony of millions of cells.
**Microbial Growth** Growth= an increase in the number of cells, not an increase in size Generation=growth by binary fission Generation time=time it takes.
Chapter 6: Microbial Growth
© 2012 Pearson Education Inc. Lecture prepared by Mindy Miller-Kittrell North Carolina State University Chapter 6 Microbial Nutrition and Growth.
Microbial Growth Physical Requirements of Microbes
Growth requirements. Growth Requirements Most common nutrients contain necessary elements (carbon, oxygen, nitrogen, and hydrogen) Microbes obtain nutrients.
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