The Erwinia chrysanthemi type III secretion system is required for multicellular behavior.
Enterobacterial animal pathogens exhibit aggregative multicellular behavior, which is manifested as pellicles on the culture surface and biofilms at the surface-liquid-air interface. Pellicle formation behavior requires production of extracellular polysaccharide, cellulose, and protein filaments, known as curli. Protein filaments analogous to curli are formed by many protein secretion systems, including the type III secretion system (TTSS). Here, we demonstrate that Erwinia chrysanthemi, which does not carry curli genes, requires the TTSS for pellicle formation. These data support a model where cellulose and generic protein filaments, which consist of either curli or TTSS-secreted proteins, are required for enterobacterial aggregative multicellular behavior. Using this assay, we found that hrpY, which encodes a two-component system response regulator homolog, is required for activity of hrpS, which encodes a sigma54-dependent enhancer-binding protein homolog. In turn, hrpS is required for activity of the sigma factor homolog hrpL, which activates genes encoding TTSS structural and secreted proteins. Pellicle formation was temperature dependent and pellicles did not form at 36 degrees C, even though TTSS genes were expressed at this temperature. We found that cellulose is a component of the E. chrysanthemi pellicle but that pellicle formation still occurs in a strain with an insertion in a cellulose synthase subunit homolog. Since the TTSS, but not the cellulose synthase subunit, is required for E. chrysanthemi pellicle formation, this inexpensive assay can be used as a high throughput screen for TTSS mutants or inhibitors.
Yap
Mee-Ngan
MN
Department of Plant Pathology, 1630 Linden Dr., University of Wisconsin-Madison, Madison, WI 53706, USA.
Yang
Ching-Hong
CH
Barak
Jeri D
JD
Jahn
Courtney E
CE
Charkowski
Amy O
AO
D000222:Adaptation, Physiological; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D018441:Biofilms / Q000254:growth & development; D002482:Cellulose / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D016974:Dickeya chrysanthemi / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D005964:Glucosyltransferases / Q000235:genetics / Q000502:physiology; D016254:Mutagenesis, Insertional; D021381:Protein Transport; D018085:Regulon; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D013696:Temperature; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; C077481:Crl protein, Bacteria; D002482:Cellulose; D005964:Glucosyltransferases; C063760:cellulose synthase (GDP-forming)