mesopohiles

 generation time
​can be visually determined by 
plotting the log phase cell number vs time.
 The slope of the line is  predictable. 

review question:
why is it useful to know the generation time of a bacterial species?

 try this problem.
submit your answer in writing in class Monday 3/10.

please show all of your work.

​Salmonella enterica has a  generation time
of 30 minutes. If you start with
10 bacteria, how many will you have in 3 hours?

two formulas used

review question:
​
a population of
M. tuberculosis
will double every 14 hours. 
If you start with 50 bacteria in a closed batch system, how many bacteria will you have after 56 hours?

C6H12O6

review question:
what is meant by a bacterial species generation time?

Halophiles adapt to osmotic stress by storing loads of
organic solutes in their cytoplasm.
this is called an 
​osmolyte strategy.
which helps balance the high salt concentration of their
environment.

bacterial growth measurements rely on a 
"closed pure batch system"
where all the required ingredients for growth are added to the culture at the start of the process. nothing else is added or removed during  the reaction. this type of system produces a predictable growth curve exhibiting four distinct phases:
lag, exponential, stationary, and death

example:
E. coli has a generation time of 20 minutes.
​If you start with one cell, how many cells will you have after 2 hours?

Environmental factors influence how well bacterial grow including pH, temperature, water activity, macro and micro nutrients and O2

     salt loving bacteria??
yup, some bacteria thrive in very salty conditions. salty = high NaCl

they're called halophiles

   manipulating
   the equation:
       n = t/g

 some halophiles also rely on a
 salt in strategy
    stockpiling inorganic ions like KCl in their
cytoplasm to balance
 the salinity in their environment. 

below info explains what oxygen is used for during metabolic reactions. it is not required information

 
  g = generation time (minutes or hours)
  t = time of exponential growth
  n = number of generations
​        

xtra credit question:
explain the function of
oxygen during cellular respiration

  we use generation time in to predict how bacteria will grow in different environments. 

optimum growth rate vs salinity

exponential phase (log/logarithmic phase):
doubling will continue at a constant rate =
the # of number of cells doubles with each time interval. plotting the cell number vs time produces a straight line and the slope = growth rate of the bacteria.
the slope of this line depends on growth conditions.

optimum growth rate vs oxygen concentration

review question:
describe the categories of bacteria in reference to oxygen requirements.

optimum growth rate vs pH

review question:
describe one adaptation used by bacteria to accommodate the extremely high or low  concentration of H+ of their environment. 

​ generation times
differ based on species and environmental conditions. 

and now we're back to required information below...

review question:
bacterial growth curves rely on the use of a closed batch system during culturing. what is that?

other bacteria can withstand and even thrive in acidic or alkaline conditions.
one acidophiles is Picrophilus.
it thrives in crazy acidic environments
like volcanic lakes exhibiting a pH of 0.06. 

one alkaliphiles is Alkalibacterium tumefaciens
it thrives in environments with pH levels > 10

optimum growth rate vs temperature

review question:
do you think bacteria that are pathogenic to humans would be extreme alkaliphiles? explain your answer.

this pic shows the covalent  bonds of glucose

 step two: calculate Nt
  (number of cells present after
    6 generations if you start with one E coli cell) 

Nt = N0 x 2^6

Nt = 1 x 64

​ 64 cells will be present after 2 hours 

 E. coli doubles in 20 minutes under ideal conditions but if nutrients are sparse, that number is significantly longer. 

  effect of environmental influences on bacterial growth

each of these bonds was made using energy and that energy is stored in that bond. 

nutrients and growth factors 

aerobic vs anaerobic bacteria

meso = middle

microbial growth in a laboratory is very different from microbial growth in real life.
 in a lab setting, ​microbes are:
*grown in nutrient-rich media for rapid growth
*grown in precise temperatures for optimal growth
*grown in pure cultures (only one type of microbe)
  without competition
*grown with favorable pH and O2 levels

So, in a lab, there's often rapid exponential growth while
in nature, growth is slower and inconsistent.  

review question:
a population of E coli is being grown in a closed batch system. E. coli has a generation time of 20 minutes.
you start with 10 cells.
​how many cells will you have after 3 days?

chapter 9:

 E. coli can double in 20 minutes
 M. tuberculosis doubles in 14 hours. 

microbial growth in a laboratory is very different from microbial growth in real life.
 in a lab setting, ​microbes are:
*grown in nutrient-rich media for rapid growth
*grown in precise temperatures for optimal growth
*grown in pure cultures (only one type of microbe)
  without competition
*grown with favorable pH and O2 levels

So, in a lab, there's often rapid exponential growth while
in nature, growth is slower and inconsistent.  

some bacteria use O2 during a process of cellular respiration.






​

this process assembles a molecule called ATP.
ATP is used by the cell to store its energy.
​ the cell uses the energy stored in food to assemble the ATP. 
​

energy in food is stored in the covalent bonds of the atoms that make up food.

the cell processes food as glucose.
​Glucose is C6H12O6.


​






​
the release of energy (exergonic reaction) when glucose is broken down is used to bond together atoms to form a different molecule called ATP. 

Once the energy is released from glucose breaking apart,
the atoms of C, H and O from the C6H12O6 have leave the cell.
these atoms are now considered waste products.
the C and the O from the C6H12O6 bond together to form CO2 which is carbon dioxide. the CO2 is released from the cell as waste gas. 
well, what to do with the H?
here's where the oxygen that the cell "breathes" in is used.
 this oxygen bonds to the Hydrogen left over from the glucose.

Oxygen and Hydrogen bond to form water H2O.
the H2O leaves the cell as waste. 

so oxygen is taken in by cells so it can bond to the leftover hydrogen from your food

which forms which is then released as waste. its true!  

if oxygen is not present, cells may rely on a different process to build ATP called
 fermentation. whole other story...

     
                   step one: calculate n
   (how many generations will there be in 2 hours)
                         we are solving for n
                    n =  number of generations
 
 1.  first we have to figure out how many minutes are        in two hours.
      there are 60 minutes in one hour
      so "t"  would be = 2 hours x 60 minutes per hour
      "t" = 120 minutes 

 2. second we set up the equation    n = t/g
      n = 120 minutes time period/
                                       20 minutes generation  time
      n = 6 generations in 120 minutes

review question:
describe one adaptation used by bacteria to accommodate the extremely high or low salinity 
of their environment. 

 optimum: growth rates are the highest at the optimum temperature/pH levels
  minimum: the lowest temperature/pH at which the organism can survive and
                       replicate is its minimum growth temperature/pH.
  maximum: the highest temperature and pH at which growth can occur is its
                       maximum growth temperature and pH.

calculating
​ generation time

review question:
explain the four stages of a a bacterial growth curve.

     adaptations to permit growth in extreme pH:
*cell membrane modifications
*proton pumps which pump H+ out of the cell to maintain a               neutral pH
*specialized proteins that can do not denature
        (maintain their structure) under extreme pH
* pH sensing mechanisms can detect changes in outside pH               and respond to maintain homeostasis. 


 acidophiles (low pH) exhibit highly charged proteins and        membranes resistant to H+
 alkaliphiles (high pH) exhibit negatively charged cell walls and use sodium pumps to help maintain pH 

death phase:
bacteria run out of nutrients and die. 

 most bacteria are neutralophiles which thrive
at neutral pH levels.
ex: Escherichia coli
Staphylococcus
 Salmonella  

molecules that a bacterium can't make on its own and must get from outside the cell are called growth factors. 
examples: vitamins, amino acids, nucleotides

lag phase:
bacteria adapt to growth conditions as they mature

review question:
bacteria that are pathogenic to humans are usually mesophiles. Why?

generation time  
​is determined during the exponential growth phase
(log phase)

xtra credit question:
read this article
https://pmc.ncbi.nlm.nih.gov/articles/PMC7024382/
what is described as an application of halophilic bacteria in medicine?

stationary phase:
​exponential growth cannot continue indefinitely due to dwindling food and increasing wastes leading to stationary phase

the time it takes for a bacterial population to double in size is called the
generational time

generation time
also differ based on factors such as temperature, moisture and the availability of nutrients 

 
  Nt = number of cells at a certain time point

  No = initial number of cells

   n = number of generations

sporulation (spore formation) allows bacteria to survive harsh conditions. 

some bacterial species utilize oxygen differently than others.
obligate aerobes require O2 to survive
obligate anaerobes can't tolerate O2
facultative bacteria can grow with or without O2
bacteria needing very low O2 levels are called microaerophiles

bacterial growth