Bacteria, Viruses, and ProtistsBacteria Basics |
What effects do pH levels have on the growth of bacteria? |
The pH is the measure of the hydrogen ion activity of a solution. The pH scale ranges from 0 (very acidic) to 14 (extremely alkaline or basic). The pH, or concentration of hydrogen ions (H ) in an environment, is critical to bacterial growth because it can affect enzyme activity. An extremely high or low pH can inactivate enzymes or disrupt cell processes. (For more about pH levels, see the chapter “Basics of Biology.”)
The following table shows the pH ranges and the optimum pH that several different organisms require for growth:
Organism |
pH Range |
pH Optimum |
Thiobacillus thiooxidans (also called Acidithiobacillus thiooxidans; consumes sulfur and produces sulfuric acid) |
1.0–6.0 |
2.0–3.5 |
Lactobacillus acidophilus (ferments sugars into lactic acid) |
4.0–6.8 |
5.8–6.6 |
Escherichia coli (associated with bladder infections) |
4.4–9.0 |
6.0–7.0 |
Nitrobacter spp. (important in the nitrogen cycle) |
6.6–10.0 |
7.6–8.6 |
Nitrosomonas spp. (oxidizes ammonia into nitrite) |
7.0–9.4 |
8.0–8.8 |