Fibrils as extracellular appendages of bacteria: their role in contact-mediated cell-cell interactions in Myxococcus xanthus

Social behavior in the myxobacterium Myxococcus xanthus involves epicellula r, peritrichous appendages called fibrils. These are polysaccharide organel les containing a set of tightly adhering proteins. It is proposed that cell -cell contact is perceived by the fibrils and is mediated by the action of a fibrillar ADP-ribosyl transferase. Fibrils or fibril-like organelles have also been found on a variety of other gram-negative bacteria and at least one archaeon, and may mediate cell-cell contact between the bacteria themse lves or between the bacteria and their eukaryotic host cells. (C) 1999 John Wiley & Sons, Inc.