How Many Bacteria Species Can Coexist on a Single Hand? (And do girls really have cooties?)

Sounds like a riddle, but it’s not trivial. We’ll get back to that in a minute. First consider the scenario: The class arrives from physical education. Today’s activity was mat ball, a variation of dodge ball involving lots of kids and lots of contact with balls and mats. They’re pumped, a little sweaty and out of breath, and one or two are a few seconds late—probably not because they were washing their hands! Would you have students wash their hands in this scenario? Not likely. It’s just not part of the lesson plan.

We accept a certain lack of sanitation mostly because it’s not feasible to allow 26-30 kids to wash their hands several times a day. We try to take solace in the hand sanitizers, though rumor has it there’s no substitute for warm water, soap and a minute of scrubbing.

Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped. Photo by Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU. Wikimedia Commons.

So what’s the big deal? Most bacteria on our skin are harmless or beneficial, right? How many could there be anyway? Well, recently published a story, Women lead men in bacteria types, hands down  that might surprise you. Researchers were surprised to find the incredible number of different bacteria species found among 51 college students’ hands and the very low number of species shared by all students. Further, there was a difference between left and right hands. And finally, there was a significant difference between men and women.

According to the news article,

They [researchers] identified 4,742 species of bacteria overall, only five of which were on every hand . . . The average hand harboured 150 species of bacteria. Not only did individuals have few types of bacteria in common, the left and right hands of the same individual shared only about 17 per cent of the same bacteria types . . .

Researchers suspect differences between left-and right-hand bacteria diversity have to do with each hand’s interactions with environment that can alter the hand’s conditions in terms of oil or salinity, for example. Differences between men and women might have to do with hormone production or slight variations in pH. Researchers commented that, for the subjects involved in this study, hand washing did not appear to remove the bacteria. It is important to note the study did not measure mass of bacteria present or population sizes for each species, only the diversity of species present.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

The National Science Education Standards Content Standard F states:

As a result of activities in grades 5-8, all students should develop understanding of

  • Personal health
  • Populations, resources, and environments
  • Natural hazards
  • Risks and benefits
  • Science and technology in society

The ideas in this news article connect to the bullets above. The following discussion highlights the ideas in the list.

Ask students if they’ve ever had a bacterial infection. What caused it? What are bacteria? Many will state they are harmful, disease causing germs. How common do they believe bacteria are? Are they in contact with any right now? How do they protect themselves against bacterial disease? Lead students to understand that many kinds of bacteria are harmless and, in fact, beneficial. Our digestion is aided by bacteria, for example. Bacteria are used in the production of yogurt and cottage cheese, among other foods. You can show them photomicrographs indicating bacteria are distinct cells, but quite small. Bacteria impact our personal health in both positive and negative ways.

How are bacteria connected to populations, resources and environments? Remind students that a group of the same kind of bacteria living in the same area is a population. Can a human hand be an adequate environment with resources to support a bacteria population? How many kinds of bacteria do you think might be able to coexist on a single human hand? Entertain all students’ guesses. Share only the numbers from the story with them. How do their guesses compare with the numbers reported?

Try some true or false questions:

1. There is no difference in the kinds of bacteria found on the same person’s right and left hand.

2. Men and women have the same kinds of bacteria on their hands.

3. Among a group of people, there is a high number of different kinds of bacteria that all people share.

Share the rest of the findings reported in the article. Ask students to generate inferences to account for the variation reported. What questions can they generate related to the findings? What kind of tests do they think would be good to conduct next and why?

You can connect the idea of natural hazards to changes in bacteria populations if you care to. After a flood for example, the biggest threat is disease due to polluted water, from overflow of sewage mixing with drinking-water supplies. At times like these, the bacteria populations found on flood-ravaged persons’ hands can be expected to differ from those found under normal conditions.

What are the risks and benefits involved in controlling bacteria through various methods: sanitation, sterilization, irradiation, and antibiotics, for example? What are the risks and benefits of using helpful bacteria to control or minimize the occurrence of harmful bacteria in food?

What role does technology play in public health policies regarding available vaccinations, medicines, and public education campaigns? See the Centers for Disease Control webpage for additional ideas and information at

To find lessons and activities that would support this topic of study, please search the MSP2 Educational Digital Library – Terms such as germs or bacteria will get you started.

We Want Your Feedback

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at

This post was originally written by Mary LeFever and published November 10, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 2/29/12 by Jessica Fries-Gaither.

All A Twitter About Math

Keeping up professionally takes time and effort and sometimes seems overwhelming. Following a few well-chosen educators or organizations can really help lighten the load. I am a big fan of Twitter. I am amazed at the wealth of wonderful resources that I discover through tweets. If you are interested in delving into the world of Twitter or perhaps are just looking for a few, good folks to follow, check out the following collections from the Best Colleges Online blog.

The 50 Best Twitter Feeds for Math Geeks

50 Essential Twitter Feeds for STEM Educators

We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts, subscribe via email, or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at

Teacher Tools that Integrate Technology: Wikis

This article was written by middle school science teacher Todd Williamson for the Integrating Technology column of Beyond Penguins and Polar Bears, an online magazine for elementary teachers. All versions of this article are licensed under a Creative Commons License.

If you’ve used a search engine like Google or Yahoo anytime in the past two years or more, you have undoubtedly run across results from Wikipedia. If you haven’t been exposed to Wikipedia, the idea may surprise you. Wikipedia is a user-created, -edited, -maintained, and -patrolled encyclopedia. Anyone can sign up for an account and add information about the topics covered in the encyclopedia. That information is then reviewed by other users, verified when possible, or marked as unverified if necessary. Wikipedia is a shining example of the collaborative power of the Internet. It is also possible to have that collaborative power in your own classroom, usually for free!

What Is A Wiki?
Wikipedia is just a large example of this month’s teacher tool: the wiki. The name comes from the Hawaiian word for “quick.” In its most simple form, a wiki is a web site that can be edited by multiple users. Wikis in Plain English, a video from Common Craft, gives a quick overview of a simple form of the wiki.

The wiki web page starts in a very simple, very blank form. It resembles a blank word processing document. Anyone with basic word processing skills can get started working on a wiki. Learning to use the “Link” button is what makes the wiki come to life. In Wikipedia, terms in each entry are linked to their corresponding Wikipedia entry. In your classroom wiki, you could have one main page that contains an outline of an intended course of study for the year, with hyperlinks to pages with information about each topic. What makes a wiki different from a static web page is the fact that you, as the teacher, will not be the only person entering information.

Wikis in the Classroom
Let’s take the course of study mentioned above as the example: Start with a single wiki page that outlines the concepts that will be covered throughout the year. Focusing a little more specifically on science, let’s say you intend to cover: weather, systems of the body, and electricity. Obviously there is a tremendous range of information that can fall under each of those categories.

As with any teaching strategy, wikis can exist as teacher-directed or student-directed exercises. On the teacher-directed end, some teachers choose to use their classroom wiki to seed their students’ learning. An example of this would be finding several web sites or videos online and linking or embedding them into the page for weather. This page can be used to give students an overview before they start the unit. The teacher controls the layout of the wiki, perhaps even locking the page for editing by others.

On the student-directed end, other teachers use the same idea, but allow their students to scour the Internet for the information. This allows students to choose what information is important to their learning.

Another idea involves using the wiki to summarize class information. For example:

After completing a section on the water cycle, Jeffery goes in the wiki and posts information about each of the stages. Jeffery happens to not be your most studious child, and he mixes up the concepts of evaporation and condensation. Allison logs on and reads the water cycle page, catches the error, and is immediately able to go in and fix the mishap. Allison also notes that there is more than one type of collection, giving details of surface runoff and percolation. Brittany, who hates to read, logs in and embeds a video from YouTube showing the stages of the water cycle.

But What If
The exchange between Jeffery, Allison and Brittany above probably sounds like the ideal. The reality is, at some point, Angel is going to log in and post some colorful explanation of a system of the human body, or delete someone’s hard work…or any number of other scary possibilities. The great thing about a wiki is that all changes are archived. As the teacher, you are capable of seeing just who made each and every change, when they worked on it, and go back to a previous version of the wiki before Angel’s little stunt.

Wikis in the K-2 Classroom
The revision and editing ideas above are perfect for students who are familiar with the computer and word processing. For the younger student, a wiki is a wonderful tool for introducing word processing. The K-2 classroom wiki will likely be more about adding information than editing. For example, in a class unit on community helpers, students could be grouped together to come up with sentences about firefighters, police officers, doctors, and other community helpers. Once all students had a sentence about a community helper, they could add that information to the wiki.

Another possibility would be to use the wiki to keep track of weekly spelling lists. The teacher could post the list and link each word to a page where students could add the definition and sentences using the word. This would be a wonderful tool to use when new students move in during the school year. Parents could review the words that the class had studied previously. This, of course, would not be limited to new students; any parents could help their child review previous learning. Though the younger students might not get to use all the aspects of the wiki, there are still plenty of possibilities for this tool.

Setting Some Ground Rules
The ground rules you set from the beginning will determine the success or failure of a wiki. They must be put in place early and adopted by all users to ensure the greatest value from the wiki. These rules can include everything from how often changes should be made, to what types of content can be uploaded, and down to the nitty-gritty aspects, like what font sizes and colors to use.

One major issue in this new digital world is copyright. Wikis provide an excellent opportunity to focus on the topic of documentation. Here the issue is not so much plagiarism as it is verification of information. Students often think citation of sources is a way for teachers to “get them” when they don’t do it correctly. With a wiki, the focus shifts to documentation as a way for users to get more information about a topic.

Another slippery slope with technology tools like a wiki is equitable access and grading. There are ways of grading a wiki that involve students making “significant contributions” to the wiki during a certain time period. The key is to make sure there is a clear definition of “significant contribution.”

Ideally, the grade for the wiki is only a small portion of the student’s overall grade. It is difficult to know for certain when Allison and Brittany come to you and say they were working together over the weekend but only Allison logged in. Your relationship with your students is important in these situations.

Yet another major point is picking a wiki service that allows you to create the usernames and passwords for your students. Some services require that students have email addresses, others do not. Wikispaces, one of the more popular wiki providers, inputs the teacher’s list of usernames and passwords so the teacher can know who logs on and when.

Getting Started
Starting a wiki is a simple process. One big decision to make at the start is who will have access to your wiki. Some wikis are public, which means they are open for all users to read and edit, like Wikipedia. Others are protected, available for everyone to read but only registered users to edit. Some wikis are kept entirely private and only registered users are able to read or edit the pages. You can start your wiki as a private wiki until “things are rolling” and then open it up for outsiders to view.

One wiki service provider, Wikispaces, offers free/inexpensive ways for educators to start their own wikis (

The site walks you through the basic process. First you must create a username and password. This username allows you to access your wiki, as well as any others to which you may decide to subscribe.

Next, you will be asked some questions about your wiki. Create a space name which will become the URL for your wiki. Decide about the visibility of your wiki – public, protected, or private. Certify that you will use the Wiki for educational purposes and you’re on your way. Wikispaces provides a tutorial to get you started once you’ve registered.

The last thing you need to get your wiki rolling is usernames and passwords for your students. Wikispaces makes this easy. Rather than having the students sign up for Wikispaces accounts, you are able to control their usernames and passwords. All you have to do is create a comma separated document with your students’ names, usernames, and passwords. For example: Allison Smartypants, asmartypants, wiki*01

Students may figure out that they can later change their usernames, but remind them that as you track changes to the wiki, you only know the usernames you set up. This can be played up as necessary to prevent changes, since you can’t give BabyGurl1229 a grade because you don’t know which student she is!

A Powerful Tool
Wikis really are one of the most powerful tools of Web 2.0. The implications for education are immense. We are teaching students who have grown up in a digital world and need to see the relevance of the topics we are covering. Wikis provide a way to make classroom content relevant as well as technology content. Students will be allowed to take part in a collaborative experience that will be useful in their later job experiences. Remember, however, since creating the wiki is a collaborative process, the ideal is that no one person has too much control over the finished product. Not even you as the teacher!

Useful Links

Two wiki service providers:



For more information about wikis and wiki service providers:

A website that compares different wiki providers. You input features you are interested in, and it lists available sites.

A wiki about wikis created for the North Carolina Middle School Association Conference in March 2008. Includes links to examples of classroom wikis and other resources.

Teachers First Wiki-Walkthrough
An overview of the use of wikis in all content areas.


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at Post updated 1/3/2012.