Transfer of TN916-like elements in microcosm dental plaques

Abstract

Microcosm dental plaques were grown from an inoculum of human saliva in a constant-depth film fermentor. The inoculum contained four tetracycline-resistant streptococcal species, each of which contained a Tn916-like element. This element was shown to transfer to other streptococci both in filter-mating experiments and within the biofilms in the fermentor.

FIG. 1

(a) Tn916 showing the positions and names of the primers used in this study. The open reading frames of Tn916 are represented by unfilled arrows showing the probable direction of transcription and are named as described in the work of Flannagan et al. (4). The arrows labeled “H” show the positions of the HincII sites. Primers are shown as filled triangles (the point of a triangle shows the direction of priming) labeled with the names of the primers. The bottom line is the scale in kilobases. (b) HincII-digested genomic DNA from Tet^r species isolated from the CDFF experiment and probed with a labeled PCR product derived from the xis and int genes present on Tn916. Lanes: 1, S. salivarius SSa10 (SSa172 showed a hybridization pattern identical to that of SSa10); 2, S. mitis SM0; 3, S. oralis SO0; 4, S. gordonii SG0; 5, S. parasanguinis SP72; 6, S. gordonii SG240 (SG336 and SG408 showed hybridization patterns identical to that of SG240); 7, S. sanguinis SS218 (SS221, SS240, and SS408 showed hybridization patterns identical to that of SS218).