Most of the tests you performed involved a color change to the media or the bacterial cells due to a change in pH and the presence of a pH indicator. What metabolic process was most often involved in the observed color changes?

Acid production

Explanation:

Most bacteria make by-products during multiplication. Bacteria that undergo lactic acid and acetic acid production via a process called fermentation will produce an acid. If there is an indicator in the media that would react with these acids the color change will appear. This will give the scientist an indication that a by product has been made and the pH of the by product is low.