<unk>  is a genus of Gram-negative bacteria in the class Alphaproteobacteria. Its best-known member is<unk>  crescentus, an organism ubiquitous in freshwater lakes and rivers; many members of the genus are specialized to oligotrophic environments.
Caulobacter
Actinobacillus
Chromobacterium
Candida 
Streptococcus
Escherichia coli
Lactobacillus
Legionella