Acids, Alkalis, and Bacterial Growth Inhibition
Hard
Do acids and alkalis both stop bacteria from growing? You prepare solutions of acid and base at 2%, 4%, and 8% concentrations. Paper disks soaked in each solution go onto agar plates streaked with two types of bacteria: Micrococcus luteus and Serratia marcescens.
After 24 hours in an incubator, you measure the zone of inhibition around each disk. Both acids and alkalis slow bacterial growth. Higher concentrations create larger clear zones around the disk.
Hypothesis
The hypothesis is that the stronger the alkali or acid, the higher the inhibition of bacterial growth.
Method & Materials
You will prepare concentrations of acids and bases, soak paper discs in them, inject bacteria culture into Petri dishes, and incubate the dishes for 24 hours.
You will need Microccus luteus and Serratia marcesceus culture, Petri dishes filled with blood agar, concentrated solutions of acid and base, paper discs, syringes, an incubator, goggles, gloves, and a lab coat.
Results
The results of the experiment show that the hypothesis should be accepted. The higher the concentration of acid/alkali, the more bacteria it kills. This experiment is useful because it tells us what conditions which are not suitable for bacteria survival.
Why do this project?
This science project is interesting because it explores how different concentrations of acids and alkalis affect the growth of bacteria. It also shows us how bacteria can be beneficial to us.
Also Consider
Variations to consider: Will all bacteria react the same way to acid and alkali? What other methods are able to kill bacteria? How can you minimize the effect of random error in this experiment? The following bacteria types can be used as alternatives for this experiment: Clostridium Perdringens, Clostridium Botulinum, and Mycobacterium Tuberculosis.
Full project details
Additional information and source material for this project are available below.Related videos
These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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