Plot the response of a culture to diauxic growth on glucose...

Plot the response of a culture to diauxic growth on glucose and lactose based on the following: $\mu_{\mathrm{g} \text { lucose }}=1.0 \mathrm{~h}^{-1} ; \mu_{\text {lactose }}=0.6 \mathrm{~h}^{-1} ; Y_{\text {glucose }}=Y_{\text {lactose }}=0.5 ;$ enzyme induction requires 30 min to complete. Plot cell mass, glucose, and lactose concentrations, assuming initial values of $2 \mathrm{~g} / \mathrm{l}$ glucose, $3 \mathrm{~g} / \mathrm{l}$ lactose, and $0.10 \mathrm{~g} / \mathrm{l}$ cells.

Key Concepts

Time Series Data Plotting

Plotting time series data of cell mass and substrate concentrations is crucial for visualizing the dynamics of microbial growth. Such plots typically show the initial rapid growth on the preferred substrate, a temporary cessation of growth during the lag phase, and resumed exponential growth on the second substrate, thus providing a clear visualization of the diauxic growth pattern.

Exponential Growth Phase

The exponential growth phase is characterized by a constant and maximal specific growth rate as long as favorable conditions and an optimal substrate are available. In a diauxic growth scenario, this phase occurs twice: first when the preferred substrate is available, and then after the lag phase when the organism has adapted to metabolize the second substrate.

Lag Phase

The lag phase represents a period of adjustment where microbial cells change their gene expression and synthesize new enzymes necessary for the metabolism of a secondary substrate. Even though substrates are available, growth temporarily pauses until the required enzymatic systems are activated, which is visible in a dip or plateau in growth-associated plots.

Biomass Yield

Biomass yield is the ratio that describes how much cell mass is produced per unit of substrate consumed. This concept is essential in analyzing growth kinetics because it links substrate consumption to cell growth, and variations in yield can indicate differences in metabolic efficiency on different substrates.

Substrate Utilization Order

When presented with multiple carbon sources, microorganisms often consume the substrate that allows a higher specific growth rate first. This prioritized usage results in a sequential rather than simultaneous utilization of substrates, with the preferred substrate being exhausted before the alternate substrate is metabolized.

Enzyme Induction Delay

Enzyme induction delay refers to the time lag required for the cells to synthesize the necessary enzymes needed to metabolize a less preferred substrate. During this lag phase, there is little to no growth increase as the organism is reprogramming its metabolic machinery, which is a critical factor in the overall diauxic growth response.

Diauxic Growth

Diauxic growth is a biphasic growth pattern observed when an organism utilizes two different substrates sequentially rather than simultaneously. Typically, the organism preferentially metabolizes the substrate that supports the fastest growth rate, leading to an initial phase of exponential growth followed by a lag phase when the preferred substrate becomes depleted, and then a second growth phase as the organism adapts to and begins consuming the alternative substrate.

Specific Growth Rate

The specific growth rate is a measure of how quickly a microbial population increases in number per unit of time under given conditions. This rate is substrate-dependent and plays a crucial role in determining which substrate will be utilized first, as the organism tends to grow faster on substrates that provide a higher specific growth rate.

Transcript

Please give Ace some feedback