Ecological behavior of plasmids and resistance to lead of Enterobacter agglomerans isolated from soil

Abstract

Soil samples taken monthly in 1990 from five parks outside Tokyo were examined for Enterobacter agglomerans. A total of 348 strains were isolated and 250 of them were tested for the presence of plasmids by DNA agarose gel electrophoresis. All the isolates carried at least two kinds of plasmids. Those isolated from July to September showed four or five kinds of plasmids (group I) and those isolated from January to June and from October to December showed two or three kinds of plasmids (group II). A majority of the plasmids detected were of 1, 500 or fewer base pairs. The isolates were tested for the Pb²⁺ resistance; group I strains were more resistant to lead than group II strains. It is presumed that bacterial plasmids are related with the ecosystem of soil and the resistance to lead in E. agglomerans.