Effect of the tropical grass Brachiaria.pdf

ARTICLE IN PRESSMicrobiological Research 161 (2006) 80—91KEYWORD Bioremedi Microbial enumerati Phytoreme Respiratio Rhizosphe 0944-5013/$ - s doi:10.1016/j.
Correspond fax: +49 711 45 E-mail addrwww.elsevier.de/micresEffect of the tropical grass Brachiaria brizantha (Hochst. ex A. Rich.) Stapf on microbial population and activity in petroleum-contaminated soil Nicole Merkla,b,
, Rainer Schultze-Krafta, Marianela AriasbaInstitute of Plant Production and Agroecology in the Tropics and Subtropics, Department of Biodiversity and Land Rehabilitation, University of Hohenheim, D-70593 Stuttgart, Germany bPDVSA – Intevep (Centro de Investigacio?n y Apoyo Tecnolo?gico de Petro?leos de Venezuela S.A.), Departamento de Ecolog??a y Ambiente, P.O. Box 76343, Caracas 1070-A, Venezuela Accepted 16 June 2005S ation; on; diation; n; re effect ee front matter 200 micres.2005.06.005 ing author. Universita? 9 4207. ess: nmerkl@uni-hoheSummary The effect of the tropical pasture grass Brachiaria brizantha on numbers of bacteria, fungi and degraders of alkanes, aromatics, cycloalkanes and crude oil in petroleum hydrocarbon contaminated and uncontaminated savannah soil was evaluated. Substrate induced soil respiration and soil pH were compared between planted and unplanted soil. B. brizantha had a mostly increasing effect on microbial numbers. As an exception, growth of bacteria was not or negatively affected. Microbial respiration and pH were always lower in planted than in unplanted soil. Low pH may result from enhanced oil degradation in planted soil leading to an accumulation of organic acids. A comparable stimulation of crude oil degraders and fungi in planted soil points to the importance of fungi. Since they tolerate lower pH values than bacteria, they are considered to play a central role in oil degradation. Given that the enhancement of crude oil degradation under the influence of B. brizantha could not clearly be correlated to microbial numbers and activity, other factors like