Author(s)

T. Al-Ostad, N. Al-Mansour & E. Al-Saleh

Abstract

The exposure of the environment in Kuwait to crude oil pollution has detrimental effects on the ecological systems. The selective pressure created by the addition of crude oil is expected to impact the bacterial community structures of affected ecosystems such as the nodule bacteroids by enhancing the growth of crude oildegrading and/or tolerant microbiota. In the present study, the effect of crude oil on the structure of the crude oil-degrading nodule bacteroids community of Arachis hypogaea is investigated. Sequence analysis of 16S rDNA amplified from nodule-bacteroids isolated from Arachis hypogaea grown in crude oil untreated and treated soils demonstrated the tendency of Gram negative bacteroids (β-proteobacteria and γ-proteobacteria) to prevail in treated soils. Crude oil mineralization studies showed that predominant bacteroids have higher rates of crude oil mineralization (5.5 µg/min) compared to Gram positive bacteroids (2.1 µg/min). Furthermore, the effect of crude oil addition on nodules size, number and distribution was recorded. Bigger nodules (diameter of 3.13±0.058mm) were detected in untreated soil compared to that of treated soil (diameter of 1.97±0.122mm). In addition, the distribution of nodules on different parts of roots of untreated and treated plants was significantly different (P<0.05). Higher numbers of nodules were detected in the upper parts of the roots of Arachis hypogaea grown in untreated and treated soils (124±0.455 and 79±1.10 nodules/plant respectively) compared to that observed in the lower parts of the roots (76±1.13 and 7±0.31 nodules/plant respectively). However, highest number of nodules (200±0.361 nodules/plant) was recorded for plants grown in untreated soils followed by that of treated soils (86±1.4 nodules/plant). These results are discussed in the context of using Arachis hypogaea to restore degraded soils and to bioremediate crude oil contamination in Kuwait. Keywords: arachis hypogaea, nodule, crude oil, bacteroids, 16S rDNA, proteobacteria.

Keywords

arachis hypogaea, nodule, crude oil, bacteroids, 16S rDNA, proteobacteria.