Microbiology notes for 9 – 25 , 28, 30, 10 - 2 – 09 part 2

I. Exponential growth vs. logarithmic growth
Exponential growth: 2x (where the x is the number of generation we have had since we just had one bacterium) = number of bacteria at a given time
Logarithmic Growth – only part of bacterial growth cruve is exponential
II. How an individual bacterium divides
a. Replication of chromosome(DNA) – have single circular chromosome, DNA will be copied by the enzyme DNA polymerase(enzyme that synthesizes new DNA molecules complementary to template strand(DNA is Double-Stranded, interacting via complementary bases(A&T(held together by 2 hydrogen bonds) and C&G(held together by 3 hydrogen bonds)).) Will need two complete copies of circular chromosome 1 for each of the 2 cells. When synthesized the bacterial chromosome is attached to inside of plasma membrane upon replication) components
b. Elongation of cell – new cell envelope stuff = red blue Cell stuff
Min proteins stop FtsZ from working; they bounce from one end of cell together stop from working else where because center is the only place.
c. Formation of FtsZ ring at septum – pinching in middle of cell; chromosomes separate either side of cell.
d. Building of new cell envelope components at septum
2. Continued) bacteria generation times:
E. coli ~ 15 minutes ~ 5 million bps in chromosomes
Staphylococci ~ 30 minutes
Generally to see a colony it has to be about 1 billion bacteria
Mycobacterium tuberculosis ~ 22 – 23 hours to divide
Different generation times is caused by difference in type of bacteria and its cell wall composition
Bacteria chromosome size affects generation time. They range in size from about 1 million base pairs(bps) to 8 to 10 million base pairs.

III. Phases of Bacterial Growth curve (in culture…not in Nature)
a. Lag phase – is because of the math of it. A. Bacterial cell division getting started. Generation times not as rapid as will be during Exponential Phase (b). Bacteria are making ATP, cell envelope stuff, enzymes like DNA polymerase, FtsZ…
b. Exponential phase(Log Phase) B. During this phase generation time is shortest; nutrients abundant as result of the nutrients bacteria have no problem making the things needed to copy new cells (bacteria easily able to make all components needed for division
c. Stationary phase – (C) # of deaths = # of new bacteria, bacteria running out of nutrients and as a result they are much less able to make all the enzymes they need to make the bacteria divide and also lack of food  some bacteria dying
d. Death phase - (D)# of deaths » # of new bacteria, cell division essentially stopped because nearly out of food, lack of food also causes deaths of existing bacteria suicide at high population densities common among bacteria Has receptors and signaling molecules When to dense own enzymes can no longer diffuse and therefore the bacteria lyses themselves.

IV. Generation time = 0.301(t-t0)/(log10N-log10N0)
What are the implications of bacterial generation times on diagnosis and treatment of disease
Can humans adapt as quickly as bacteria can evolve
Why don’t bacteria have mitochondria? These are wrong answers.
- Most bacteria are free-living; they do not live on/in a host/in a host cell
- A definition is not a reason
Prokaryotes don’t have membrane bounded organelles, and mitochondria are membrane bounded organelles.
- Bacteria use ATP as energy currency just like all other living things do.
Bacteria are like bigger mitochondria
Divide like mitochondria
• Mitochondria have own DNA and replicate on their own using the same cell division steps that bacteria do. And because mitochondria generate ATP in a way that’s identical to how bacteria generate ATP and the mitochondria can be killed by many antibiotics if injected into cell.
• Biologists think mitochondria are decedents from bacteria (ex. Of symbiotic relationship between eukaryotic cells and mitochondria
Type 3 section systems
• Similar to bacterial flagella, similar to ATPsynthase
• Act like a hypodermic needle to inject virulence factors into host cells or at a minimum to squish virulence factors out into the open world
Organisms developed form other organisms and therefore parts of cells have developed from other parts of cells. Different from falsifiable claim is they were all set up at one time.

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