Population dynamics of chesapeake bay virioplankton: total-community analysis by pulsed-field gel electrophoresis - PubMed (original) (raw)

Population dynamics of chesapeake bay virioplankton: total-community analysis by pulsed-field gel electrophoresis

KE Wommack et al. Appl Environ Microbiol. 1999 Jan.

Abstract

Recognition of viruses as the most abundant component of aquatic microbial communities has stimulated investigations of the impact of viruses on bacterio- and phytoplankton host communities. From results of field studies to date, it is concluded that in most aquatic environments, a reduction in the number of bacteria on a daily basis is caused by viral infection. However, the modest amount of in situ virus-mediated mortality may be less significant than viral infection serving to maintain clonal diversity in the host communities directly, through gene transmission (i.e., transduction), and indirectly, by elimination of numerically dominant host species. If the latter mechanism for controlling community diversity prevails, then the overall structure of aquatic viral communities would be expected to change as well over short seasonal and spatial scales. To determine whether this occurs, pulsed-field gel electrophoresis (PFGE) was used to monitor the population dynamics of Chesapeake Bay virioplankton for an annual cycle (1 year). Virioplankton in water samples collected at six stations along a transect running the length of the bay were concentrated 100-fold by ultrafiltration. Viruses were further concentrated by ultracentrifugation, and the concentrated samples were embedded in agarose. PFGE analysis of virus DNA in the agarose plugs yielded several distinct bands, ranging from 50 to 300 kb. Principal-component and cluster analyses of the virus PFGE fingerprints indicated that changes in virioplankton community structure were correlated with time, geographical location, and extent of water column stratification. From the results of this study, it is concluded that, based on the dynamic nature of the Chesapeake Bay virioplankton community structure, the clonal diversity of bacterio- and phytoplankton host communities is an important component of the virus community.

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Figures

FIG. 1

FIG. 1

Contour-clamped homogeneous electric field PFGE of Chesapeake Bay virioplankton and densitometric scan of virioplankton PFGE fingerprints. Lane A, molecular size markers; lane B, virioplankton PFGE fingerprint from a water sample collected at station 744 on the August 1995 cruise. (C) Densitometric scan of fluorescence intensity from the lane B virioplankton PFGE fingerprint. The densitometric scan data were divided into seven molecular size classes, shown at the far right. Molecular size markers are in kilobases.

FIG. 2

FIG. 2

Virioplankton PFGE fingerprints of water samples analyzed in the study. (I) August 1995 water samples from stations 858, 845, 818, 744, and 724 (lanes A to E, respectively). (II to IV) May 1996 (II), June 1996 (III), and July 1996 (IV) water samples from stations 908, 858, 845, 818, 744, and 724 (lanes A to F, respectively). Lanes λ, molecular size markers (kilobases) specific for each pulsed-field gel.

FIG. 3

FIG. 3

Computer-generated banding patterns based on virioplankton PFGE fingerprints shown in Fig. 2. Gel and lane designations are identical to those for Fig. 2. Banding patterns were used to calculate a similarity matrix (data not shown). Band positions were standardized to a single marker lane. Molecular size markers are in kilobases.

FIG. 4

FIG. 4

Dendrogram based on a similarity matrix of virioplankton PFGE fingerprint banding patterns from all water samples.

FIG. 5

FIG. 5

Three-dimensional plot generated from principal-component analysis of virioplankton PFGE fingerprint data. Positions of samples are marked according to cruise date (August [formula image], May [★], June [⧫], or July [•]) and station.

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