#3: Cell Yield Values under Variety of Growth Conditions Consider a series of ba
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#3: Cell Yield Values under Variety of Growth Conditions Consider a series of batch culture experiments performed using the bacterium Escherichia coli with glucose as the limiting substrate, and iron provided at different levels ranging from iron sufficient to iron deficient conditions. The data in the following table present the initial glucose level in the growth medium, the initial and final iron levels in the growth medium, and the initial and final cell concentrations for seven different batch culture experiments. Using this data, calculate the apparent yield of cell mass on glucose substrate for each batch, and then plot these values (dependent parameter) as a function of the initial level of iron provided (independent parameter, suggested plot with a logarithmic axis). Comment on the trend for eld on glucose as a function of the initial level of iron provided in the batch. component of a couple of enzymes in the electron transport chain of Iron is an important procaryotes and eucaryotes. Can you theorize qualitatively why the cell yield on glucose decreases with the lower iron concentration? Table P7.4 Cell Batch Growth Data for Glucose Limited/ Iron Deficient Conditions Cell Concentrations (gdw/L)Iron Concentrations (ppb) Initial Glucose (gr/L) Final 0.9 0.8 0.55 1.8 1.7 1.3 1.1 Initial 1,484 72 1.7 5,265 335 61 20 Final 1,210 23 Initial 0.009 0.0085 0.0075 0.05 0.05 0.05 0.05 2 761 47 0 0 4 ppb-parts per billion or ?g/kgExplanation / Answer
Cell yield on glucose decreases with lower iron concentration because for most microorganisms, iron is essential for many reactions. Iron influences cell composition, inter-mediary metabolism, secondary metabolism and enzyme activity of the bacterial cells. It is essential for tricarboxylic acid cycle, elctron transport chain, amino acod and pyrimidine synthesis and DNA synthesis.
Iron plays important metabolic role on the regulation of cell cycle. It activates the cyclin/ cyclin dependent kinase complexes, favoring the progression to the S-phase. Due to lower iron concentration, the cell cycle is inhibited and hence the decreased cell yield.
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