Campylobacter jejuni is a major cause of human diarrheal disease in many industrialized countries and is a source of public health and economic burden. C. jejuni, present as normal flora in the intestinal tract of commercial broiler chickens and other livestock, is probably the main source of human infections. The presence of C. jejuni in biofilms found in animal production watering systems may play a role in the colonization of these animals. We have determined that C. jejuni can form biofilms on a variety of abiotic surfaces commonly used in watering systems, such as acrylonitrile butadiene styrene and polyvinyl chloride plastics. Furthermore, C. jejuni biofilm formation was inhibited by growth in nutrient-rich media or high osmolarity, and thermophilic and microaerophilic conditions enhanced biofilm formation. Thus, nutritional and environmental conditions affect the formation of C. jejuni biofilms. Both flagella and quorum sensing appear to be required for maximal biofilm formation, as C. jejuni flaAB and luxS mutants were significantly reduced in their ability to form biofilms compared to the wild-type strain.Campylobacter jejuni is a gram-negative, curved-to-spiral rod with polar flagella and grows best in a microaerophilic environment ranging from 37°C to 42°C (5, 8, 15, 29, 32). In the United States, it is estimated that approximately 2.1 to 2.4 million cases of campylobacteriosis occur annually, with a cost of $8 billion (20,21).Symptomatic infections of campylobacteriosis may consist of an acute onset of watery diarrhea, abdominal pain, fever, and the presence of blood and leukocytes in the stools. The disease is usually self-limiting, lasting from 2 to 11 days (5,7,20). Long-term secondary effects of infection may include reactive arthritis, Reiter's syndrome, and Guillain-Barré syndrome (19,23).Campylobacter spp. are considered normal flora of the gastrointestinal tract of a number of domestic animals and birds, such as commercial broiler chickens (1,2,6,9,38). Campylobacter spp. shed by these birds can enter waterways, which in turn can act as a source of contamination for other animals. Campylobacter infections occur through oral routes, including ingestion of contaminated water, unpasteurized milk, and undercooked or raw foods, such as poultry (6, 9, 38). However, consumption of raw milk and undercooked poultry is considered the major source of Campylobacter infections.In most settings, natural, industrial, or clinical, bacteria are usually found in biofilms rather than in the planktonic state seen in the laboratory (7, 24). Current theories suggest that transition to a biofilm state is dependent on the nutritional content of the surrounding medium. Previous research has demonstrated that biofilm formation takes place via multiple steps, and upon completion, a mature, dynamic, three-dimensional structure is formed (11,16,24,26). Some of the current biofilm models indicate that the participation of flagella and pili is important in the growth of the microcolony, especially during the early stages o...