Investigative Case - Living in an Alkaline Environment

At the end of this module, students will be able to:

• Show many ways in which Mono Lake water and distilled water are different;
• Demonstrate that the survival of common soil bacteria declines as pH increases;
• Examine the behaviors, adaptations, energy transfer, and diversity of organisms in an alkaliphilic habitat.

This activity is appropriate for introductory Geoscience, Environmental Science, and Biology classes for major or nonmajors. It contains both hands-on lab and internet research components in which students learn about water pH, bacterial behaviors in and adaptation to high alkalinity, and the diversity of alkaline-tolerant bacteria. Part three of this activity is a WebQuest. To learn more about the philosophy behind and design of WebQuests, read an introduction to WebQuests.

This Investigative Case Study is from the Living in an Alkaline Environment three-part activity, part of Microbial Life Educational Resources. Access materials and information needed to complete this activity.

Key Concepts:

• Mono Lake is an extreme environment, with a pH of 10 and a high salt and mineral content
• High pH denatures proteins and dissolves fats
• Survival of common soil bacteria declines as the pH rises
• The limited number of organisms able to tolerate Mono Lake's extreme environment means less competition for resources and fewer predators for those able to live there
• Organisms expend valuable metabolic resources to survive Mono Lake's extreme conditions
• Life will adapt in order to take advantage of available sources of energy and nutrients
• Alkaliphiles maintain an internal pH of 7.5-8.5, regardless of the environmental pH
• At high pH, alkaliphilic bacteria activate a sodium-ion pump, which begins a process that lowers the internal pH by transporting hydrogen ions into the cell
• Alkaliphilic enzymes have a special composition that protects them from being denatured
• Alkaliphiles' cell membranes have a special composition that protects them in Mono Lake's highly-alkaline conditions

Key Skills:

• Comparing different substances; Measuring pH; Measuring specific gravity
• Inoculating agar plates; Counting colony abundance on an agar plate; Creating a graph
• Conducting a WebQuest; Synthesizing information from a WebQuest

Materials:

• Part 1: Student sheets, Distilled water; Table salt; Baking soda, Epsom salt; Borax; Detergent containing phosphate (e.g., Spic & Span); Sodium hydroxide (Sodium hydroxide is readily and inexpensively available as lye in hardware and grocery stores); Dropper bottles; pH meters, papers, or strips; Cooking oil; Wax paper; 100 ml, 500 ml and 1000 ml beakers; Specific gravity hydrometer or rods/spheres that indicate density by floating or sinking; 2 dishpans; Dozen eggs; 4 teaspoons; Paper towels or sponge; Heat source (e.g., Bunsen burner, candle, alcohol burner); 2 spoons with insulated handles (or oven mitt); Dropper bottle of vinegar; microscope whose image can be displayed on a computer or projection screen; Microscope slide; Cover slip; Tissue or other absorptive material; Cellular stain (if necessary for clarity).
• Part 2: Student sheets; Soil samples; 2 Liter Flask, 40-50 Petri dishes; Hot plate w/ stirrer and stir bar; Aluminum Foil; pH strips, litmus paper, or pH meter; 40 g tryptic soy agar (powder, pre-made, or Easy-Gel), 0.1 M Hydrochloric Acid; 0.1 M Sodium hydroxide.
• Part 3: Computer lab with internet connection.

Living in an Alkaline Environment consists of three major activities. These activities may be utilized as a whole or as individual activities according to topics covered, materials needed, and time required for each. The third activity is a WebQuest that explores the ecology of Mono Lake. For a general description of WebQuests, visit an introduction to WebQuests.

Time (One day is considered to be a 50-minute class):

• Part 1 - How different is Mono Lake water different from Distilled Water: (2 Days) Day 1: Visit the activity stations; Day 2: Conduct the demonstrations & discussion.
• Part 2- Testing Bacterial Survival Over a pH Range of 7 - 10: (3 days) Day 1: Inoculate plates; Day 2: Brief observation; Day 3: Final observation & graphing.
• Part 3- A WebQuest Exploring the Life and Ecology of Mono Lake: (3 days) Day 1: Begin WebQuest; Day 2 - 3: Finish WebQuest.

At the end of these activities, students should be able to:

• Provide ways in which Mono Lake water and distilled water are different;
• Demonstrate that the survival of common soil bacteria declines as pH increases;
• Show an understanding of the behaviors, adaptations, energy transfer, and diversity of organisms in an alkaliphilic habitat.

Student responses should be supported by evidence from credible sources such as peer-reviewed journal articles, textbooks, etc.

Another measure of success for these activities is general student feedback-this may include comments made by students regarding the activity itself, if students continue discussing the topic after or outside of class time, or if students contribute to the discussion with their own thoughtful questions (during the activity itself, subsequent class periods, or outside of class).

National Education Standards

These activities conform with National Science Education Standards. See specific National Science Educational Standards met by Living in an Alkaline Environment.

These activities have been adapted from the Living in an Alkaline Environment module, which is part of the Microbial Life Educational Resources Project. More information regarding this activity may be found at the original Living in an Alkaline Environment site.