We human beings are severely outnumbered by microorganisms. The average human body contains about ten trillion cells, but has approximately ten times as many microorganisms, or 100 trillion microorganisms. It is about time you were introduced to these passengers you cart around with you!

Most of the microorganisms that call your body “home” are components of your normal microbiota. If they stay in balance and in the specific location they belong (the correct address as it were), they do us no harm. In fact, many of these organisms provide essential services for you, their host. This normal microbiota is one of our main sources of such necessary substances as niacin, thiamine, riboflavin, folic acid, biotin, and vitamin K. In addition, these resident microbes serve to protect us from invasion by other potentially pathogenic microorganisms. They do this by competing for food, space, and occasionally producing antimicrobial substances such as antibiotics that tend to discourage the arrival of new neighbors.

Microbes also proliferate outside the human body. They are crucial to our survival on this planet as they help maintain the balance of living organisms and chemicals in our ecosystems. Microorganisms form the basis of the food chain in the oceans and lakes of the world. Some can “fix” nitrogen gas from the air into the form that other organisms may utilize, i.e. organic compounds. Some microorganisms are photosynthetic, and as such, capture the energy in sunlight for the rest of us to exploit. They are used to produce chemicals such as acetone, alcohols, and many drugs. Microorganisms are employed by the food industry to produce such items as sauerkraut, cheese, yogurt, bread, etc. These food industry “employees” don’t even demand minimum wage!

Nevertheless, microorganisms can be the cause of human disease, infection, and even death. In our quest to maintain good health, it is essential to understand why the relationship between man and microorganism goes awry and how to prevent the process from causing severe damage. Thus, this microbiology laboratory manual will function to initiate you into this world which is quite unfamiliar to most individuals. It is a fascinating discipline which we look forward enthusiastically to sharing with you.

As with most of life’s experiences, you will get out of your microbiology laboratory class what you put into it. It is extremely important that you come to lab familiar with the day’s activities. Make it a point to always read the exercises you will perform BEFORE you come to lab. This manual was designed so that it is quite self-instructional. You should be able to proceed with the activities without a lengthy explanation from your instructor, although your instructor is always available if you have a question. Students who pre-read and pre-organize their laboratory time inevitably finish their labs faster than those who do not, and they learn more in the process. Post tests are provided in each exercise to allow confirmation that you have achieved understanding of the major objectives.


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Laboratory Exercises in Microbiology Copyright © 2022 by Anne Mason M.S. and Jill Raymond Ph.D. is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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