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# Detection and avoidance of a natural product from the pathogenic bacterium Serratia marcescens by Caenorhabditis elegans

## Details

**Authors** Pradel et al.

**Year** 2007

**Publisher** Proceedings of the National Academy of Sciences of the United States of America

**Discipline** Biology

[Read it at the publisher](https://doi.org/10.1073/pnas.0610281104) 
10.1073/pnas.0610281104

## In authors' words

### Abstract

The nematode Caenorhabditis elegans is present in soils and composts, where it can encounter a variety of microorganisms. Some bacteria in these rich environments are innocuous food sources for C. elegans , whereas others are pathogens. Under laboratory conditions, C. elegans will avoid certain pathogens, such as Serratia marcescens , by exiting a bacterial lawn a few hours after entering it. By combining bacterial genetics and nematode genetics, we show that C. elegans specifically avoids certain strains of Serratia based on their production of the cyclic lipodepsipentapeptide serrawettin W2. Lawn-avoidance behavior is chiefly mediated by the two AWB chemosensory neurons, probably through G protein-coupled chemoreceptors, and also involves the nematode Toll-like receptor gene tol-1 . Purified serrawettin W2, added to an Escherichia coli lawn, can directly elicit lawn avoidance in an AWB-dependent fashion, as can another chemical detected by AWB. These findings represent an insight into chemical recognition between these two soil organisms and reveal sensory mechanisms for pathogen recognition in C. elegans .

### What they set out to do (purpose)

Can nematodes distingusih their environments?

### What they found (results)

Nematodes can Distinguish.

## Commentary

### In short

The nematodes are distinguishing this chemical from the rest of their environment and drawing the connection to the dangerous pathogen so that they can avoid it.

### In more detail

This next study by Pradel et al 2007 is a good example of chemotaxis in action. Caenorhabditis elegans, a nematode, is heavily present in soil. In its soil environment, there are nutrients it needs in order to survive, but there are also deadly pathogens it must avoid. In the lab, C. elegans systematically avoids the bacterium Serratia marcescens. This is shown in their experiment where they placed a nematode in a bacterial field and in a few hours the nematode had left that bacterial field. “By combining bacterial genetics and nematode genetics, we show that C. elegans specifically avoids certain strains of Serratia based on their production of the cyclic lipodepsipentapeptide serrawettin W2.”

The nematodes are distinguishing this chemical from the rest of their environment and drawing the connection to the dangerous pathogen so that they can avoid it. “Recognizing and distinguishing among pathogenic bacteria represents a potentially valuable behavioral adaptation, which C. elegans demonstrates. It also demonstrates learning behavior, as it can alter its olfactory sensors after being exposed to a pathogen, trying to avoid the contact again.

**Patterns it shows** D

**How to cite this** Pradel et al. (2007). Detection and avoidance of a natural product from the pathogenic bacterium Serratia marcescens by Caenorhabditis elegans. Proceedings of the National Academy of Sciences of the United States of America.