Caulobacter is a genus of Gram-negative bacteria in the class Alphaproteobacteria. Its best-known member is Caulobacter crescentus, an organism ubiquitous in freshwater lakes and rivers; many members of the genus are specialized to oligotrophic environments.
Although Caulobacter is not commonly appreciated as a cause of human diseases, Caulobacter isolates have been implicated in a number of cases of recurrent peritonitis in peritoneal dialysis patients. One study has identified the species C. crescentus and C. mirare as the cause of a disease of the moth Galleria mellonella; the absence of identified distinct virulence factors in C. mirare may suggest that other Caulobacter species have pathogenic potential.