This study assessed the profile of plasmids in the culturable heterotrophic bacterial isolates from organic swine waste (SW) and inorganic (NPK) fertilizer amended tropical soils of the Niger Delta region in Nigeria. Plasmid DNA was extracted and analyzed by agarose gel electrophoresis. Plasmid analysis of 70 fertilizer utilizing bacterial isolates revealed the presence of plasmids with molecular weights ranging from 4.0 to 40.1kb. Twenty two (31%) out of the seventy isolates carried at least

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... e kind of plasmid while forty eight (69%) possessed none. Seventeen (77%) of the isolates with plasmids had one plasmid each of molecular weight approximately 23.1, 25.2 or 35.7kb. Five (23%) possessed two plasmids each of molecular weight approximately 23.1 and 40.1kb, 4.3 and 32.7kb, 4.0 and 40.1kb, 23.5 and 40.1kb or 23.1 and 40.1kb respectively. Bacterial isolates taken from organic fertilizer-amended plots showed highest plasmid incidence (38%) whereas isolates from the control or non-amended plot showed the lowest plasmid incidence (25%). Statistical inferences revealed that plasmid carriage in the bacterial isolates were independent of fertilizer treatments.