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Module 1 - Process of Science
What is a model system anyway?

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Model Systems and why we study P. syringae

In Module 1 - Social Science, you learned that Yersinia pestis, the cause of bubonic plague, has some similarities to the plant pathogen P. syringae. Here you will learn why scientists sometimes study one organism to learn about another organism


The number and diversity of organisms in the world is staggering. As biologists, we try to understand how each of these organisms has evolved and interacts with its environment and other organisms. To cope with the fact that there are far more organisms to be studied than biologists to study them, scientists use MODEL SYSTEMS.

A model system is a particular organism that is studied in great detail as a representative of other organisms like it. Instead of studying each organism individually, we study model systems and make inferences about what happens in other similar organisms.

To be chosen as a model system, an organism must be part of an interesting group of organisms, be accessible to all scientists, and have characteristics that make it easy to work with in the laboratory.

For instance, E. coli is a model bacterium because it is easy to study, an important pathogen, and it teaches us about biological processes common to many bacteria.


Escherichia coli - model system for many different bacteria

Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped.
Credit: Photo by Eric Erbe, digital colorization by Christopher Pooley (USDA, ARS, EMU)
Source: Wikipedia (link to picture)

In animal studies, mice are commonly used as a model system for studies on mammals and the fruit fly Drosophila melanogaster is a model system studying genetics


The common fruit fly - model system for genetics of higher organisms

Drosophila melanogaster, male (left) and female.
Source: Wikipedia (link to picture)

Arabidopsis thaliana, a relative of broccoli, cauliflower and other cruciferous plants, is an important model system for studying plant genetics. It was chosen because it has a short life cycle, is physically small and easy to grow, and has a small genome.


Arabidopsis thaliana - model system for plant research

Source: Boyce Thompson Institute Plant Genome Research Outreach (link)

The bacterium Pseudomonas syringae is used as a model system for the study of bacterial plant pathogenesis, in part because it is a pathogen of the model system plant, Arabidopsis thaliana. In addition, it is safer to work with than human pathoigens such as Yersinia pestis. As you learned in Module 1 - Social Science those bacteria share similarities in their virulence mechanisms.


Pseudomonas syringae - model system for other bacterial pathogens

Photo: Gordon Vrdoljak,
Electron Microscopy Laboratory, U.C. Berkeley

To learn more about model systems in Biology consult the Wikipedia Model Organism Page

A hyperlinked list of model systems in Biology can be foundat the Joe Kunkel website at UMass