Genetic analysis of the capsule polysaccharide (K antigen) and exopolysaccharide genes in pandemic Vibrio parahaemolyticus O3:K6.
BACKGROUND
Pandemic Vibrio parahaemolyticus has undergone rapid changes in both K- and O-antigens, making detection of outbreaks more difficult. In order to understand these rapid changes, the genetic regions encoding these antigens must be examined. In Vibrio cholerae and Vibrio vulnificus, both O-antigen and capsular polysaccharides are encoded in a single region on the large chromosome; a similar arrangement in pandemic V. parahaemolyticus would help explain the rapid serotype changes. However, previous reports on "capsule" genes are controversial. Therefore, we set out to clarify and characterize these regions in pandemic V. parahaemolyticus O3:K6 by gene deletion using a chitin based transformation strategy.


RESULTS
We generated different deletion mutants of putative polysaccharide genes and examined the mutants by immuno-blots with O and K specific antisera. Our results showed that O- and K-antigen genes are separated in V. parahaemolyticus O3:K6; the region encoding both O-antigen and capsule biosynthesis in other vibrios, i.e. genes between gmhD and rjg, determines the K6-antigen but not the O3-antigen in V. parahaemolyticus. The previously identified "capsule genes" on the smaller chromosome were related to exopolysaccharide synthesis, not K-antigen.


CONCLUSIONS
Understanding of the genetic basis of O- and K-antigens is critical to understanding the rapid changes in these polysaccharides seen in pandemic V. parahaemolyticus. This report confirms the genetic location of K-antigen synthesis in V. parahaemolyticus O3:K6 allowing us to focus future studies of the evolution of serotypes to this region.
Department of Pathology, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610, USA. yuansha.chen@pathology.ufl.edu
Yuansha
Y
Chen
Jianli
J
Dai
J Glenn
JG
Morris
Judith A
JA
Johnson
D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology; D000954:Antigens, Surface / Q000235:genetics* / Q000276:immunology; D016667:Bacterial Capsules / Q000235:genetics / Q000276:immunology; D017353:Gene Deletion; D006801:Humans; D007194:India / Q000453:epidemiology; D008969:Molecular Sequence Data; D019081:O Antigens / Q000235:genetics / Q000276:immunology; D058873:Pandemics; D011135:Polysaccharides, Bacterial / Q000235:genetics* / Q000276:immunology; D014735:Vibrio Infections / Q000453:epidemiology / Q000382:microbiology*; D014736:Vibrio parahaemolyticus / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification
D000942:Antigens, Bacterial; D000954:Antigens, Surface; C030659:K antigens; D019081:O Antigens; D011135:Polysaccharides, Bacterial