Curlin is the structural subunit of the curli fimbriae. Curli are coiled surface structures that assemble preferentially at growth temperatures below 37 degrees Celsius. Curli can bind to fibronectin. The minor subunit is the nucleation component of curlin monomers. Coexpression of cellulose and thin aggregative fimbriae (curli fimbrae or fibers) leads to a hydrophobic network with tightly packed cells embedded in a highly inert matrix that confers cohesion, elasticity and tissue-like properties to colonies (PubMed:24097954). Part of the curli surface structure. Under control of the CsgD transcription factor, part of the csgBAC/ymdA operon. When disrupted in a cellulose-synthesizing strain (with a functional bcsQ gene), cellulose is made but colony morphology indicates no curli are made. Cellulose production is abolished in E.coli K12 / MG1655 and W3110 due to a premature stop codon in bcsQ (PubMed:24097954). Belongs to the CsgA/CsgB family.