Instructions
1. Complete the virtual lab in MH Connect.
2 Write your lab report in essay format. Your report must include the following in 1-2 pages:
Introduction
Hypothesis
Methods
Results
Conclusion
Resources
Writing Tips: Lab Reports and Scientific Papers: http://www.cws.illinois.edu/workshop/writers/tips/labreports/ (Links to an external site.)
How to Write your Lab Report: https://owl.purdue.edu/owl/teacher_and_tutor_resources/writing_tutors/tutoring_lab_reports.html (Links to an external site.)
Instructions
1. Complete the virtual lab in MH Connect.
2 Write your lab report in essay format. Your report must include the following in 1-2 pages:
Introduction
Hypothesis
Methods
Results
Conclusion
Resources
Writing Tips: Lab Reports and Scientific Papers: http://www.cws.illinois.edu/workshop/writers/tips/labreports/ (Links to an external site.)
How to Write your Lab Report: https://owl.purdue.edu/owl/teacher_and_tutor_resources/writing_tutors/tutoring_lab_reports.html (Links to an external site.)
Key Concepts
Microbes adapt to a wide range of environmental conditions that include temperature, pH, osmotic pressure, atmospheric gases, and the availability of nutrients.Some microorganisms can live at extremes of each of these environmental factors based on adaptations of metabolism.Enzyme systems determine how environmental factors affect microbial growth.Environmental factors, such as temperature and pH, can disrupt the structure of enzymes, resulting in denaturation and making them unable to function.The growth of microorganisms can be controlled in the laboratory by altering environmental factors, such as temperature, oxygen content, osmotic pressure, and pH.Growth can also be controlled by placing microbes in an environment with oxygen or in a special growth chamber that contains very little, or even zero, oxygen.Microorganisms exposed to pH levels outside of their survival range will experience protein denaturation, ultimately leading to cell death.The pH scale numbers from 0-14. In the middle, pH7 is neutral,so anything less than 7 is acidic and anything above 7 is basic or alkaline.Depiction of a pH scale from 0 pink to 14 yellowpH ScaleMicroorganisms adapt to certain ranges of conditions and some live at the extreme edges of temperature or pH and can be classified by their survival range under these conditions.Microorganisms are therefore adapted to live in a specific, preferred pH range. They are classified based on the pH range they require for growth.
Organisms Can Be Classified Based on pH PreferencesClassification DescriptionAcidophile Optimum pH below 5.5Neutrophile Optimum pH near 7Alkalinophile Optimum pH above 8.0Overview
Bacterial growth depends on many environmental factors, including pH. Since microbes can survive in a certain range of pH and will thrive at a particular pH, understanding these variables allows for control of their growth. This understanding can be used, for example, to preserve certain foods or to treat infections.In this simulation, you will learn how pH, an environmental factor, can influence the growth of microorganisms.Bacteria will be exposed to variable environmental pH conditions and the effect on bacterial growth as measured by turbidity will be determined. When bacteria multiply in a broth culture, they turn the clear solution cloudy, or turbid.The lab simulation will test a given bacterial culture in a set of broths, each of which is a different pH. A hypothesis will be chosen and tested to determine the classification of the specimen based on its pH preferences.Before you begin
Microbial populations grow at different rates based on optimal pH levels. One way to measure growth is by turbidity measurements.This lab simulation will use an instrument called a spectrophotometer. This instrument quantitatively measures the amount of light that is absorbed or transmitted by molecules in solution. Different cells and culture media absorb best at a specific, known, wavelength. In this case the amount of light transmission is related to the number of bacteria present. Optical Density is the value given to the measurement of turbidity.The spectrophotometer can be used in microbiology to measure the turbidity of a culture medium. Tubes with no bacterial growth will show zero turbidity. The more growth present, the higher the reading will be. Taking measurements of turbidity, indicating bacterial growth, at various pH levels will determine the range and optimal pH for the growth of the sampled organism.spectrophotometerSpectrophotometerA spectrophotometer uses a cuvette, which is a straight-sided, optically clear container for holding liquid samples in a spectrophotometer.cuvetteCuvetteRemember that while this is a safe simulation, you should practice good laboratory hygiene protocols when translating this learning to the benchtop. This includes following aseptic technique procedures, proper handwashing, and cleaning of benchtop surfaces as you complete similar exercises in the lab setting.
My Hypothesis:An organism will have varied growth at different pH values with fastest growth at an optimum pH.
My Strategy:Inoculate pH3, pH5, pH7, pH 9 and pH 11 broths with the same organism and determine the growth in each.
My Conclusion:An organism will have varied growth at different pH values with fastest growth at an optimum pH.
Apply what you have learned: pH 3pH 5pH 7pH 9pH 11Optical density0.630.320.120.020.00Given the optical data above for each pH, what is the optimal pH for the growth of this organism?pH 3
Given the optical data above for each pH, how would the test organism be categorized?Acidophile
Collected Lab DatapH 3pH 5pH 7pH 9pH 11Optical density0.0000.4000.6000.4000.000Saved Graphs
Graph 1
Optical densitypH35791100.250.50.751