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Journal of Bacteriology, August 2009, p. 4934-4942, Vol. 191, No. 15
0021-9193/09/$08.00+0     doi:10.1128/JB.01831-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Heat-Resistant Agglutinin 1 Is an Accessory Enteroaggregative Escherichia coli Colonization Factor{triangledown} ,{dagger}

Samhita Bhargava, Brandon B. Johnson, Jennifer Hwang, Tamia A. Harris, Anu S. George, Amanda Muir, Justin Dorff, and Iruka N Okeke*

Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, Pennsylvania 19041

Received 29 December 2008/ Accepted 20 May 2009

Enteroaggregative Escherichia coli (EAEC) is an important cause of acute and persistent diarrhea. The defining stacked brick adherence pattern of Peruvian EAEC isolate 042 has previously been attributed to aggregative adherence fimbriae II (AAF/II), which confer aggregative adherence on laboratory E. coli strains. EAEC strains also show exceptional autoaggregation and biofilm formation, other phenotypes that have hitherto been ascribed to AAF/II. We report that EAEC 042 carries the heat-resistant agglutinin (hra1) gene, also known as hek, which encodes an outer membrane protein. Like AAF/II, the cloned EAEC 042 hra1 gene product is sufficient to confer autoaggregation, biofilm formation, and aggregative adherence on nonadherent and nonpathogenic laboratory E. coli strains. However, an 042 hra1 deletion mutant is not deficient in these phenotypes compared to the wild type. EAEC strain 042 produces a classic honeycomb or stacked brick pattern of adherence to epithelial cells. Unlike wild-type 042, the hra1 mutant typically does not form a tidy stacked brick pattern on HEp-2 cells in culture, which is definitive for EAEC. Moreover, the hra1 mutant is significantly impaired in the Caenorhabditis elegans slow kill colonization model. Our data suggest that the exceptional colonization of strain 042 is due to multiple factors and that Hra1 is an accessory EAEC colonization factor.

* Corresponding author. Mailing address: Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041. Phone: (610) 896-1470. Fax: (610) 896-4963. E-mail: iokeke{at}haverford.edu

{triangledown} Published ahead of print on 29 May 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, August 2009, p. 4934-4942, Vol. 191, No. 15
0021-9193/09/$08.00+0     doi:10.1128/JB.01831-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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