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Ne4ueva
7 days ago
7

1. You are given the task to quantify the bacteria in your soil sample. You do a 10-fold serial dilution of your soil sample in

sterile water and plate 1/10 of each subsequent (serial) dilution in LB agar plates with cycloheximide – an antifungal and eukaryotic cell inhibitor. If your 10–6 (ten to the minus sixth) dilution plate contains 97 bacterial colonies after two days of incubation, how many bacteria can you estimate were present in your initial soil sample (1 g of soil)? Show your calculation and briefly describe each step.
Biology
1 answer:
lana [2.1K]7 days ago
8 0
Conducting a serial dilution along with a plating experiment allows for the quantification of bacteria or microbes present in a specified volume of a soil sample. In this standard procedure, a designated volume taken from the lesser dilution is placed on a median plate, which is then allowed to incubate for the appropriate duration. The resulting colonies are counted to ascertain the overall Colony Forming Units (CFU) based on the volume of the sample that was plated and the amount of soil sample that was utilized. The calculation follows this formula: CFU/ml = Number of colonies counted × dilution factor / volume plated. In this scenario, we have: Number of colonies counted = 97, dilution factor = 10^(-6), and volume plated = 1/10 = 0.1. Therefore, the calculation proceeds as: CFU/ml = 97 * 10^(-6) / 0.1 = 97 * 10^(-7) CFU/ml. This figure represents the concentration of bacterial colonies per unit volume of the plated sample. Given that the original soil sample weighs 1g or 1000 mg, the total number of bacteria can be estimated with this formula: Amount of bacteria in original sample = 97 * 10^(-7) CFU/ml × 1/1000 mg = 9.7 * 10^(-3) CFU/mg.
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The complete question includes the following statement:

A rice grain is a fruit containing a seed. The majority of a rice grain’s dry mass is starch. Starch synthesis in rice plants occurs through the hydrolysis of sucrose followed by the linking of the released glucose molecules to form starch. The ideal temperature range for starch synthase operation in a specific rice strain is between 27°C and 30°C. Similarly, the ideal temperature range for sucrose synthase in this strain is from 30°C to 35°C.

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For rice grains to develop their starch content, the action of two enzymes is crucial: sucrose synthase, which disengages glucose from sucrose, and starch synthase, which polymerizes glucose into starch (as seen in the image).

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A temperature of 35°C significantly surpasses the optimal range required for the enzyme's activity, indicating a potential change in its structure or denaturation that would hinder starch synthase's function. A key consequence of this would be a decreased rate of starch synthesis.

What predictions can be made regarding the starch content in mature rice grains if the average growing season temperature is 33°C?

A temperature of 33°C is beyond the starch synthase activity range—even though it's still favorable for sucrose synthase—which is likely to lead to reduced starch synthesis, resulting in this crop's rice grains containing less starch overall.

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