Interpretation of growth curves

Apart from the times at which the several phases of growth occur and comparing the rates of growth we can also derive other information from growth curves. If the organism is given more than one substrate to grow on we can see which substrate it uses preferentially. Most substrates are used sequentially through Bacteria and not at the same time. For example if Escherichia coli is grown in a minimal medium containing glucose and lactose, it will use up all the glucose first before switching on the lac operon and using up the lactose growth rate 2 in Figure 4. This can be explained in terms of the energetics of the compounds: the bacterium derives more ATP from the metabolism of glucose than lactose so has a faster growth rate and uses this compound preferentially.From this it can be seen in which diauxic growth always follows the pattern of a high growth rate followed by a lower one.