Dynamics of Prokaryotic Growth原核生长动力学.pptVIP

4.5 Environmental Factors that Influence Microbial Growth 4.6 Nutritional Factors that Influence Microbial Growth Heterotrophs Carbon source is organic carbon Medically important bacteria Autotrophs Carbon source is inorganic carbon Perform carbon fixation, the conversion of inorganic carbon into organic carbon Photoautotrophs use photosynthesis CO2 + H2O ? Glucose + O2 4.7 Cultivating Prokaryotes in the Laboratory Complex Media Contain a variety of biomolecule precursors Concentrations of precursors can vary between media Often, the source of the precursors are extracts, which are water-soluble substances Examples Nutrient agar Tryptic soy agar Blood agar Defined Media Known amounts of chemicals and biomolecules are formulated into the medium More expensive than complex media Selective Media Generally used for the propagation of particular bacteria MacConkey agar selects for Gram- enterics Bismuth sulfite agar cultures Salmonella and Proteus species to the exclusion of other bacteria Differential Media Media that can distinguish two or more groups of bacteria in a mixed culture Providing Appropriate Atmospheric Conditions Increased CO2 Capnophiles (15% CO2) Hemophilus Neisseria Microaerophilic - low levels of oxygen Anaerobe - killed by prolonged exposure to oxygen Dynamics of Prokaryotic Growth Chapter 4 4.1 Principles of Prokaryotic Growth Robert Koch (1843-1910) Developed the strategies for cultivating bacteria Defined growth requirements Media formulations First to use agar for semisolid media Bacterial replication Binary fission Doubling time varies by species and conditions Growth can be calculated Nt = N0 x 2n Nt = total cells in a given time N0 = starting population of cells n = number of cell divisions Assume t = 20 min (3 per hour) 3 x 4 hours = 12 doublings If N0 = 10 then 10 x 212 = 40,960 bacteria 4.2 Bacterial Growth in Nature Biofilms Bacteria in nature tend to attach to solid surfaces These bacteria encase themselves in polysaccharide coatings to