CHAPTER 4 Prokaryotic Growth Principles of Prokaryotic Growth o Divide by binary fission Increased in size and doubled its components This attributes to bacteria ability to grow exponentially o Microbial growth Used to discover the relative size of cells in a given population Defined by the number of cells in a population o Generation doubling time The time it takes for the population to double in number Varies on the species and the conditions of the environment E coli is approx 20 minutes while Mycobacterium is about 12 hours o Calculating the doubling time Nt No 2n Where Nt is the population at a give ntime t and No is the initial population N is the number of cell divisions Bacteria Growth in Nature o Natural and the laboratory growing environments differ greatly Ex a type of prokaryote may create slime layer to attach to rocks in nature but not in the lab o Biofilms Can live suspended in an environment but attach to surfaces as well Attach by creating a polysaccharide layer while living in communities Biofilm forms when planktonic free floating bacteria adhere to a surface where they multiply and synthesize slime layers to which unrelated cell may attach and grow Slime layers have characteristic open channels through which nutrients and waste can pass Cells communicate by synthesizing and responding to chemical signals an exchange that is important in establishing structure 65 of bacterial infections result from biofilms cystic fibrosis dental plaque and ear infections able to resist antibiotics well because of the protective slime layer help sewage degradation and bioremediation are enhaced with biofilm planktonic vs same species in a biofilm much more resistant o Interactions of mixed microbial communities Prokaryotes other grow in the presence of other microbes Can be hospitable to each other foster bacteria that otherwise would not survive Ex one bacteria s waste could be another s food source Anaerobes that cannot grow with o2 can grow in the mouth because other bacteria consume the o2 Can be non hospitable Can create toxins that kill off competetors Obtaining a pure culture o Pure culture A colony of cells where each cell is similar same species Easier to study but do cells in pure cultures may not bahave as they do naturally Only 1 can actually be grown in the lab In order to cultivate need sterile all microbial growth killed aseptic techniques procedures that minimize the chance of other organisms being introduced and a culture medium a medium that has the nutrients that will encourage cell growth o Cultivating Bacteria on a Solid Culture Medium Requirements solid culture medium a media container that can be maintained in an asceptic condition and a method to separate bacteria cells A single bacterium will multiply to form a colony or pure culture Agar a polysaccharide extracted from marine algae Used to solidify a liquid culture medium Unlike other gelling agents gelatin agar stays solidified at room temp Not destroyed at high temperatures Nutrients that would be destroyed at high temperatures are added at lower temps preserving Remains solid 95 degrees C at the temp which most microbes grow Petri dish the two part container made of glass or plastic excludes airborne microbes Agar plate Petri dish filled with Agar o Streak plate method Simplest and most commonly used technique for isolating bacteria A sterilized inoculating loop is dipped into microbial containing solution Parallel streaks that reduces along each quadrant o Maintaining stock cultures Stock culture a culture derived from a pure colony that is stored for use in later inoculum procedures Stored in fridge in an agar slant a tube held at a shallow angle as the medium solidifies creating a larger surface area Lyophilized freeze dried of Bacterial Growth in Laboratory Conditions Closed or batch systems o Systems without renewing nutrients or any mechanism waste removal Agar tubes or flasks Cell number increases in a predictable fashion and then eventually declines Follows a particular growth curve Most distinct in a broth culture because exposed to the same conditions as planktonic particles Needed to maintain continuous growth of a culture Nutrients are added and waster products are removed o Open system o The Growth curve Lag phase When the bacteria are diluted and transferred need time for considerable growth Lag phase a tooling up prior to multiplication Synthesize macromolecules ribosomes nucleic acids ATP The length deepens on the species and the conditons Less nutrients more time because need to synthesize the missing nutrients Exponential Phase Log phase Cells divide at a constant rate and their numbers increase by the same percentage each tiem interval The generation time is based on this time of active multiplication Most susceptible to antibiotics during this time laying down peptido o Activities are directed towards increasing cell mass Produce amino acids nucleotides and building blocks of proteins o Ability to precisely regulate these amounts to ensure for efficient assembly Primary metabolites compounds synthesized during this phase o A product of any rxn that is essential for growth Can be used as flavoring o Late log phase o A shift in cell activity o Nutrient depletion and waste build up cause the system to enter stationary phase If endospores initiate sporulation during this phase o o Become rounder and more resistant to chemicals radiation Composition of cell wall and membrane may occur Synthesize secondary metabolites These can be antibiotics which kill off other microbes Stationary phase No longer have supplies or energy to sustain adequate growth Population remains constant some die as other multiply Cells that dies release their components that can stabilize other bacteria Cells continue to synthesize secondary metabolites and maintain altered properties of late log stage Death phase o o o Chemostat continually drips fresh medium into culture while an equivalent amount of waste exits A constant density and generation time of log phase cells can be maintained Possible to study uniform log cells over a long period Total number of viable cells die off at constant rate Dies off slower than it multiplies Phase of prolonged decline dynamic process Marked by a very gradual decrease in the number of cells Very long phase Cells die and other cells use components constant pop flux Same as liquid but after lag grow and compete for nutrients The location of a cell in colonies determines its