Mechanism for Antibiotic Resistance Discovered

Those of us born after World War II have take antibiotics for granted. Strep throat? Ear infection? Acne? Bronchitis? Not a problem. Take the full prescribed antibiotic dose and you are cured. The reality of antibiotic resistant bacteria however, disrupts that scenario. No longer can we always trust in a full recovery from a bacterial infection after completing the antibiotic regimen. Rather than continuing to create new and different antibiotics, the trend in research is to discover the mechanisms of antibiotic resistance in order to neutralize it.

How Some Bacteria Survive Antibiotics from ScienceDaily describes how researchers at the University of Illinois, Chicago, studied bacterial action in the presence of erythromycin and related antibiotics. These drugs incapacitate the bacterial protein factories, ribosomes. All cells have ribosomes which are the site of translation in protein synthesis. Erythromycin prevents newly synthesized proteins from detaching from the two subunits of the ribosome, thus preventing the bacteria from thriving. The researchers discovered, however, that these drugs can signal the bacteria to switch a bacterial gene on that enables bacterial release of newly synthesized proteins from the ribosomes. Thus, they effectively resist the drug in a process known as inducible antibiotic expression.

The article quotes one of the researchers

Combining biochemical data with the knowledge of the structure of the ribosome tunnel, we were able to identify some of the key molecular players involved in the induction mechanism. . . .We only researched response to erythromycin-like drugs because the majority of the genetics were already known. There may be other antibiotics and resistance genes in pathogenic bacteria regulated by this same mechanism. This is just the beginning.

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

A manifestation of evolution, antibiotic resistance aligns with the Life Science standard of The National Science Education Standards, “Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.” Also related is the structure and function section of the standard: prokaryotic cell structure, the ribosome, and protein synthesis.

Ask students if they have ever had an ear infection or strep throat. What did they do about it? Lead them to disclose that they went to the doctor, were prescribed an antibiotic and took it for the full course, often 10 days. Ask if they were cured then, or did anyone suffer a recurrence within the next week or so? If yes, why? Then what did they do? Lead them to articulate the concept of bacterial resistance. Consider showing visuals of a typical animal eukaryotic cell side by side with a bacterial cell. This will highlight the size and structural difference, and enable student comprehension of how bacterial cells can colonize a eukaryotic cell. Make sure they understand the activity of the millions of bacteria cells a) consumes nutrients needed by one’s own healthy cells and b) produces waste that makes one sick.

If you’ve already discussed the characteristics of living things, cell theory and cell structure, lead students to recall the importance of ribosomes to all living cells. Ask, what might happen if the function of the ribosomes were disrupted? Students should reason that protein production would stop and the cell would die for lack of needed proteins. Inform them that this is the way some antibiotics work; they interfere with the bacterial cells’ ribosome function. (Prokaryotic and eukaryotic ribosome structure varies slightly allowing the eukaryotic ribosomes to remain unaffected.) Ask, what if the presence of the antibiotic signaled the bacteria to produce a protein (turn a gene on) that interfered with the drug’s ability to disrupt the ribosome’s work? Allow plenty of wait time for them to think this through logically. They should arrive at the idea of antibiotic resistance, even if they don’t use that phrase.

Allow students to read the first three paragraphs above and follow the links. The protein synthesis link however, is probably too advanced for middle school students and can be eliminated. Have them read the article How Some Bacteria Survive Antibiotics. Assess: what is an antibiotic? How do drugs like erythromycin work? What is inducible antibiotic expression? How might it be helpful to know the mechanisms by which bacteria resist antibiotics? Describe how antibiotic resistance is an example of evolution.

Here are some additional resources from the Middle School Portal 2 related to antibiotic resistance and bacteria: Introduction to Bacteria; Microbes: Too Smart for Antibiotics?; Microbes: What They do and how Antibiotics Change Them; and What’s making you sick?

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 msp@msteacher.org.

This post was originally written by Mary LeFever and published May 9, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.

How Is Species Defined and Why Does It Matter? The Politics of Conservation

This post focuses on the definition of species and its implications beyond science content knowledge—specifically, how the definition is related to species conservation and protection.

For example, the brown bear of the Iberian Peninsula is a different species compared with other European brown bears because it is geographically isolated, right? According to a press release, New Study Changes Conditions for Spanish Brown Bears, published by AAAS’s EurekAlert! there are just two small populations of this bear and they are threatened. One idea to help bolster their population size is to introduce brown bears from other European populations. However, this may cause hybridization and eventual loss of the Iberian Peninsula brown bear species. Further, what makes conservation biologists think the two different bears will interbreed successfully?

According to the Life Science content standard of the National Science Education Standards, middle school students should be learning concepts associated with structure and function in living systems; reproduction and heredity; regulation and behavior; populations and ecosystems; diversity and adaptations of organisms. All of these areas of study are related to the concept of species. That is, discussions in any of these areas will necessarily be founded on an understanding of the term “species.”

Can we take for granted that middle school students have developed an accurate concept of species on their own, through personal experience? Because they can distinguish cat from dog, a rose from a maple tree, and a human from an ant, is it safe to assume they have a good grasp of the concept? Not if we wish to facilitate and broaden students’ conceptual understandings to progressively more sophisticated levels.

Students understand that cats and dogs, roses and maple trees, and humans and ants do not interbreed. Thus, they have an understanding of the biological definition of species. But things can get complicated and this definition does not always fit. Another perspective assumes reproductive isolation defines species. That is, if two populations are physically or temporally isolated preventing interbreeding, then they are considered separate species. That works well conceptually for most middle school students’ experience, but what about when individuals from one geographically isolated population are introduced to another, either intentionally or unintentionally, and they successfully interbreed?

When discussions around Mendelian genetics occur, the concept of hybrid is introduced. Plants do this all the time. Is the hybrid a new species? They often can and do interbreed. Are the offspring a new species? Most would hesitate to say yes. Then do we revise our definition of species? Those reproductively isolated populations really are the same species after all?

Contrary to what most people believe, the concept of species seems to be a moving target in terms of pinning a definition on it. As such, it is open to criticism from people who believe science is supposed to be definitive. This presents an opportunity for teachers to reinforce the nature of science, and life science particularly. Living systems, from a single cell to a biome, are dynamic and not entirely definitively understood. (If they were, conservation would probably not be an issue!)

Assuming a fixed definition of species may be unreasonable. One’s definition of species is contextual, dependent upon the current issue under consideration. It is important that discussants have a common definition of species in these instances. Why? Because the focus of and outcomes of species-related discussions can determine political policy, such as what gets listed as a threatened or endangered species and receives federal funding for protection from habitat destruction or hunting.

DNA sequencing allows for almost unequivocal determination of whether individuals from two different populations are the same species, and consequently subject to the same political treatment. In the case of the Spanish brown bears, DNA sequencing suggests they are not a distinct species from other European brown bears. That means introducing bears from other populations will not supplant the Iberian Peninsula brown bears. The proposed conservation strategy is a viable one. Scientists are confident that the introduced bears will successfully interbreed with the Spanish brown bears due to the genetic similarity. This constitutes a prediction, and its accuracy will be determined only after bears are introduced into the area.

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

Consider the American Bald Eagle. It is cited as a success story of the Endangered Species Act (ESA). It has recovered from its endangered status and was delisted in 2007. This means the bird is no longer protected under federal law in terms of some kinds of hunting and habitat protection. States are free to make their own regulations regarding hunting and protection of the species.

More recently, the Northern Rocky Mountain population of gray wolf was delisted. The Western Great Lakes grey wolf population was also delisted. States that are host to these two populations have the power to regulate hunting and management of the animals. However, any wolves on National Park Service land or outside the two areas mentioned above, are under federal government protection.

How is species defined? Ask students if dogs and wolves are separate species. How do they know? Accept all reasonable responses. Are lions and tigers? Are saber toothed cats and Bengal tigers? Lead students to define species in terms of (a) macroscopic anatomy, (b) geographic isolation (lions and tigers), and (c) temporal isolation (extinct and extant cats). This discussion should highlight the difficulty in pinpointing a definition. None is incorrect, yet none is fully sufficient. This is acceptable in classroom discussions, but when conservation groups discuss species, they have to be specific. For example, in delisting the Rocky Mountain gray wolf, the documents specify the geographic region that defines the population. Individual animals falling outside the defined geographic range are not delisted and remain protected by the ESA.

Can students imagine that features other than those immediately visible could be considered in determining who is different and who is the same species? For example, in Batesian mimicry two species are physically similar, but one is poisonous to predators while the other is not. Lead students to understand that there are microscopic or chemical means of determining similarity and differences. Conversely, two populations can appear to be quite different but are chemically quite similar. (This may explain the original assumption that the Spanish brown bear was a separate species from other European brown bears.) The morphological difference is attributed to environmental influences, not genetic differences, and so it is predicted the two populations could interbreed successfully. That’s often good news for conservation management.

What do students think the Endangered Species Act is? Why is it needed? Allow them to brainstorm. Then show them pages from http://www.fws.gov/endangered/about/index.html to either confirm their list or amend it. Can they name any organisms on the list now? Call attention to species other than mammals, including plants. How do students suppose an organism gets listed/delisted? Have students investigate this question at http://www.fws.gov/endangered/species/us-species.html. Facilitate student discovery that the process is not neat and easy necessarily. Rather it can be emotional and partisan. Why?

Here are some additional resources from the Middle School Portal 2 related to conservation and wildlife management: Natural Resources, the Environment, and Ecosystems; and DDT Quest.

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 msp@msteacher.org.

This post was originally written by Mary LeFever and published March 26, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.

What Are Seed Gene Banks and How Do They Work?

Seed gene banks exist throughout the world. As you might guess, their purpose is to catalog, store, and protect as many varieties of plants as possible. These banks are useful to plant breeders trying to find crop species that are more drought or disease resistant, for example. They also provide a resource for countries in recovery after natural or man-made catastrophes. For example, after the tsunami in Malaysia in 2004, rice growers were able to obtain salt-tolerant varieties of rice not normally gown in that area. However, many seed banks are located in areas of the world where they are susceptible to destruction. Seed banks in Afghanistan and Iraq have been ransacked.

A consortium of organizations has collaborated in order to address this problem and provide a centralized, stable, reliable site for preserving and protecting world crop seeds. On February 28, 2008, the Svalbard Global Seed Vault began operating. The New York Times and ScienceDaily both reported the event. The Times article, Near Arctic, Seed Vault Is a Fort Knox of Food, is accompanied by numerous photographs and a map indicating the location of the vault. The ScienceDaily article, Thousands of Crop Varieties Depart For Arctic Seed Vault, contains one photograph and numerous links to related articles. Both articles describe the project, who is involved with the project, and why.

Did you know there are about 1,200 varieties of banana plants worldwide? Only about half have been preserved. Other food crops exhibit thousands of varieties as well. The Times notes that, in the United States, “eighty percent of maize types that existed in the 1930s are gone.” The rapid loss of crop plants on the planet heightens the need to preserve as many as possible at this time for their potential in serving future generations.

The Consultative Group on International Agricultural Research (CGIAR) maintains and coordinates seed gene banks around the world, encompassing 600,000 plant varieties. Its goal is to back up all known varieties of useful plant varieties in the Svalbard Global Seed Vault.

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

The National Science Education Standards are sometimes criticized for the lack of emphasis on plant biology. However, the Life Science Content Standard for grades 5-8 allows for elaboration on plant biology in many contexts. There are five big ideas within this content standard, none of which excludes plant biology: structure and function in living systems; reproduction and heredity; regulation and behavior; populations and ecosystems; diversity and adaptations of organisms. Teachers should strive to present instruction inclusive of all kinds of living things with respect to these five big ideas, including crop plants.

Entertain student estimates on the number of varieties of bananas, tomatoes, maize, beans, and so on. Present them with statistics reflecting the actual number of known varieties for the crops you choose. Ask what might differentiate one variety from another. Lead students to the idea of differences in optimal growing conditions and variety in tolerance with respect to things like drought, water quality, disease resistance, and yield. Ideally, you may be conducting an ongoing activity in which students grow, observe, and compare food crop varieties for some of these variables.

Can students think of any reasons to try and preserve this variety? Intended for educators, the article Plant Content in the National Science Education Standards lists several reasons for preserving plant biodiversity by virtue of the plant-derived products we depend on to maintain our lifestyle.

Students might recall the tsunami of 2004 or Hurricane Katrina. Ask them if crops that once thrived in those areas could be expected to thrive just as they did before the disasters. Lead them to the idea of salt residue left in soil. Drops of salt water on a paper towel allowed to dry will provide evidence to help students understand soil could be altered by salt water washing over it. Fresh celery or raw potato allowed to sit in salt water demonstrates the effect of salt on plants. Remind students of the Asian rice growers in the ScienceDaily article who found salt-resistant rice in the seed banks.

Imagine your students harvested 300 seeds from plants grown this year at school and you found a way to preserve them. One hundred years from now, students find those seeds and plant them in a natural setting. What do your students predict the outcomes would be? Will the seeds germinate? Will the plants thrive? Will they flower and produce seeds? What rationale do students provide to support their predictions? Lead them to understand the environment will most likely be altered from what it is now. There may be new pests, viruses, pathogens, and competitors. Tie the discussion to natural selection. Is it safe to assume that seeds preserved today can be planted 100 or 200 years from now with great confidence in their success? Then why preserve them? How should they be managed?

Recall the name “gene bank.” These banks can be conceived of as genetic repositories, not simply seed preservation sites. That means there is potential to isolate and manipulate useful genes from preserved seeds. Thus, it may not be necessary that the preserved seeds thrive but that they lend themselves to gene isolation. Periodic germination of preserved seeds followed by collection of new seeds may simulate the natural selection process and increase the probability that preserved seeds will thrive if germinated hundreds of years from now.

What about plants, such as bananas, whose seeds do not preserve well or are not reliable with respect to germination for various reasons. How can those plant species be preserved? There is no pat answer to this question; thus it is an excellent question for student inquiry. Students may propose things like cryogenics of tissues for later vegetative propagation or genomic sequencing for incorporation into some kind of surrogate seed embryo later.

Here are some additional resources from the Middle School Portal 2 related to issues of plant biodiversity and plant breeding: Thinking Green? Grow Your Own! and Seeds of the World: Journey to Forever.

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 msp@msteacher.org.

This post was originally written by Mary LeFever and published March 7, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 3/27/12 by Jessica Fries-Gaither.

A Breakthrough in Nerve Cell Regeneration

When you conjure up an image of cells, what do you see? What do you think? You may see a snapshot of an animal tissue, perhaps with actively dividing cells. That’s understandable because, as animals ourselves, we’re aware that cells come from other cells, thus the need to undergo mitosis, or cell division, frequently.

But one kind of mammalian animal cell does not fit that image—nerve cells. They do not arrange themselves as cells in a typical tissue do. Nerve cells are singular, with a long, sometimes very long, threadlike extension called an axon. And they don’t undergo mitosis frequently, except in embryos. This apparent aberration in the world of cells has puzzled scientists and medical researchers. If one could get nerve cells to behave more like other cells in terms of regeneration, a host of nerve-related diseases and damage could be reversed.

ScienceDaily published a story on January 26, 2009, reporting on exactly that kind of breakthrough, New Hope For Restoring Injured Nerves. A group of researchers at the University of Utah uncovered a pathway (a chain of molecular events) involving a gene that, when forced to be overactive, leads to repair of severed nerve cells in nematode worms. The gene is also found in mammalian genomes; thus, the researchers predict they will be able to replicate the study in mammals.

Finding a gene that produces a protein that aids in nerve cell repair in worms is not surprising. Gene theory predicts just that in organisms known to regenerate portions of their anatomy. It also is not necessarily surprising to find the same gene in mammalian systems, since evolutionary theory reveals our common ancestry. What did surprise researchers was that the pathway that results in nerve cell regeneration is not found in developing embryos.

Scientists have puzzled over the fact that nerve cells are regenerated in mammalian embryos and very young, rapidly developing mammals, but not in adults. The question was, what did mammals lose along the way to maturity? The pathway discovered in the new study “is unique in that it is not used by the nervous system during normal embryo development, yet it is absolutely required for regeneration,” one of the researchers said.

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

Middle school curriculum usually includes some study of cells, genetics, and body systems. This story provides background for some authentic discussions allowing students to apply and extend their knowledge in these three areas. At the same time, it provides opportunity to reinforce concepts in methods of science.

Ask students what happens to a worm that gets cut in half by a gardener’s shovel? To a starfish whose leg is bitten off by a predator? What is regeneration? Have they ever wondered why humans cannot do the same? Do they know that mammalian embryos and very young mammals do have the ability to regenerate? How might regeneration be related to the science of genes? What does the idea of regeneration have to do with curing paralysis in humans?

Remind students of cell theory and show them some visuals of cells, and cells in tissues, organs, and systems. Show them some nerve cells. If they’ve studied the nervous system, they already have some notions regarding nerve cell structure and function. Explain that in paralysis, the nerve is severed and, in adults, not easily repaired.

Point out that scientists have uncovered the worms’ pathway that enables their nerve cells to regenerate. Ask how such a discovery could possibly be useful in mammalian systems? Remind students that all living things share some common characteristics, like cellular structure, DNA, and the ability to respond to stimuli. Is it possible that mammalian genomes could contain the same or similar genes that enable regeneration in worms? As predicted by evolutionary theory, the answer is yes!

So why can’t we regenerate nerve cells? Remind students, or explain, that genes have to be turned on in order to produce the necessary proteins that participate in a pathway culminating in regeneration. In this study, scientists methodically “knocked out” genes, one by one, in worms until they found the one primarily responsible for nerve cell regeneration. (There actually are four genes working together.) When the scientists created conditions that enabled the gene to increase its activity, producing ample protein associated with regeneration, nerve cell regeneration was rapid in adult worms. This confirmed their hypothesis regarding the activity of a particular gene on regeneration. It also enabled them to uncover the steps in the pathway from gene to cell regeneration. Knowing the steps allows scientists to hypothesize possible ways to enhance the pathway in order to induce regeneration in mammals.

Using this story allows you to facilitate student synthesis of knowledge from perhaps three different units in their curriculum around three fundamental theories: cell theory, gene theory and evolutionary theory. It also reinforces concepts associated with the Life Science content standard of the National Science Education Standards, as well as the History and Nature of Science content standard.

Here are additional resources from the National Science Digital Library Middle School Portal 2 (MSP2): Visit Cell City; Middle School Meets Evolution; Cell Differentiation; andCell Biology Animation.

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 msp@msteacher.org.

This post was originally written by Mary LeFever and published January 27, 2009 in the Connecting News to the National Science Education Standards blog. The post was updated 3/22/12 by Jessica Fries-Gaither.

Thanksgiving Science

From the pop-up thermometer to turkey genetics, Thanksgiving offers lots of topics that can be explored through science. Thanks to Terry Shiverdecker for pulling together resources from the Ohio Resource Center collection of exemplary science, mathematics, and English/language arts resources.

Along with these resources consider asking students to conduct Internet research to answer these questions:

• What is it about a traditional Thanksgiving meal that makes you sleepy? Is it the tryptophan in turkey or something else?
• What is the science behind those golden brown and delicious dinner rolls? Hint: Maillard reaction
• Does cornstarch or flour make the best gravy?

Please share any other resources/ideas/questions/comments and have a great time!

Delicious and Nutritious
The food we use to celebrate Thanksgiving is delicious and may also be nutritious. But if we stuff ourselves we are likely to suffer the consequences. What better time to study digestion, what we get from food, and how science comes to the rescue when we over do it?

Thanksgiving Science: Tryptophacts and Tryptophantasies
Is turkey what makes you sleepy at Thanksgiving? No. Maybe. (How much did you eat?)

Food and the Digestive System
This lesson focuses on the digestive system. Students identify the major organs of the digestive system and determine the function of each organ. This Science NetLinks lesson is the first of a three part series.

Good Food, Good Health
Students explore ways in which food provides energy and materials for our bodies. In this investigation, students will use online resources to help them explore how food can affect their overall health. This lesson is the second of a Science NetLinks three part series.

Got Broccoli?
This lesson is designed to help students understand why the body needs food, and how it takes necessary nutrients as food passes through the digestive system. Students are asked to look critically at the advertising claims of foods they eat, recognizing those that ascribe unrealistic, emotional, or psychological benefits to foods, rather than nutritional benefits. Students will then create an original advertising campaign for a “forgotten” vegetable, presenting compelling, factual information about the nutrients found in these foods and the benefits derived from them.

Enzyme Salad Lab
In this activity students examine the effects of a specific digestive enzyme (bromelin) found in pineapple on a specific protein found in Jell-O.

The Effectiveness of Antacids
In this performance assessment from PALS, students design and conduct a scientific experiment to test which of four antacids would be most effective for neutralizing acid. They will rank the antacids in order from most effective to least effective and explain how they determined the effectiveness of each one. The resource is designed to assess grades 9-12 students but can be modified to be appropriate for middle level students.

Pop-Up Turkey Thermometers
How do those pop-up thermometers they put in turkeys work? It turns out that there is a little piece of a solder type material in the thermometer that melts at 185 degree F. So when the turkey reaches that temperature the solder melts, the plastic pops up, and you know it is time to eat. This bit of Thanksgiving information can be related to change of phase, heat transfer, and physical/chemical change. You could also consider a design challenge around this idea.

Matter of State
This lesson is designed to give students the opportunity to observe a phenomenon created by particle movement. Students begin to move from the fundamental concept of solid, liquid and gas to the reasoning for why the states exist under given conditions.

The Heat Is On
In this resource students discover how heat is transferred by conduction through matter by watching interactive video segments.

Turkeys and Genetics
The turkeys served on Thanksgiving Day are dramatically different from the ones served many years ago. To meet the demand for birds with more white meat, turkeys have been selectively bred and fed special diets designed to result in birds with larger breasts. Consider engaging students in a discussion of this somewhat controversial practice as a way to introduce genetics.

Modeling Mendel’s Pea Experiment
This modeling activity allows students to discover for themselves what Mendel uncovered in his famous pea experiments. It is an excellent introduction to Mendelian genetics which generates discussion and stimulates interest in Mendel’s principles. Students are encouraged to use the same observation and critical thinking skills that Mendel used.

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 msp@msteacher.org. Post updated 4/09/2012.