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Applied and Environmental Microbiology, January 2000, p. 140-147, Vol. 66, No. 1
Center of Marine Biotechnology, University of
Maryland Biotechnology Institute, Baltimore, Maryland
21202,1 Bacteriology Laboratory,
Department of Post Graduate Studies and Research in Biological
Sciences, R. D. University, Jabalpur-1 (M.P.),
India,2 and Department of Cell Biology
and Molecular Biology, University of Maryland, College Park,
Maryland 207423
Received 1 June 1999/Accepted 10 September 1999
Vibrio cholerae is indigenous to the aquatic
environment, and serotype non-O1 strains are readily isolated from
coastal waters. However, in comparison with intensive studies of the O1
group, relatively little effort has been made to analyze the population structure and molecular evolution of non-O1 V. cholerae. In
this study, high-resolution genomic DNA fingerprinting, amplified
fragment length polymorphism (AFLP), was used to characterize the
temporal and spatial genetic diversity of 67 V. cholerae
strains isolated from Chesapeake Bay during April through July 1998, at
four different sampling sites. Isolation of V. cholerae
during the winter months (January through March) was unsuccessful, as
observed in earlier studies (J. H. L. Kaper, R. R. Colwell, and S. W. Joseph, Appl. Environ. Microbiol. 37:91-103,
1979). AFLP fingerprints subjected to similarity analysis yielded a
grouping of isolates into three large clusters, reflecting time of the
year when the strains were isolated. April and May isolates were
closely related, while July isolates were genetically diverse and did
not cluster with the isolates obtained earlier in the year. The results
suggest that the population structure of V. cholerae
undergoes a shift in genotype that is linked to changes in
environmental conditions. From January to July, the water temperature
increased from 3°C to 27.5°C, bacterial direct counts increased
nearly an order of magnitude, and the chlorophyll a
concentration tripled (or even quadrupled at some sites). No
correlation was observed between genetic similarity among isolates and
geographical source of isolation, since isolates found at a single
sampling site were genetically diverse and genetically identical
isolates were found at several of the sampling sites. Thus, V. cholerae populations may be transported by surface currents throughout the entire Bay, or, more likely, similar environmental conditions may be selected for a specific genotype. The dynamic nature
of the population structure of this bacterial species in Chesapeake Bay
provides new insight into the ecology and molecular evolution of
V. cholerae in the natural environment.
0099-2240/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genetic Diversity of Vibrio cholerae in
Chesapeake Bay Determined by Amplified Fragment Length
Polymorphism Fingerprinting
*
Corresponding author. Present address: Department of
Environmental Analysis and Design, University of California, Irvine, Irvine, CA 92697. Phone: (949) 824-5527. Fax: (949) 824-2056. E-mail:
sjiang{at}uci.edu.
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