Bacterias y hongos hidrocarbonoclastas de rizosfera frijol y maiz, en un suelo contaminado con petroleo | Hydrocarbonoclastic bacteria and fungi of the rhizosphere of bean and corn, in a soil with petroleum pollution

When plants grow in soils contaminated with petroleum, an ideal habitat is created for the development of microorganisms that are able to use petroleum as a source of carbon. Microorganism reproduction increases in the rhizosphere, augmenting the possibilities of removing the pollutant. The objective of the present work was to study the relationship of hydrocarbonoclastic bacteria and fungi isolated from the rhizosphere of plants (Chamaecrista nictitans and Panicum sp.) growing in a polluted soil in Minatitlan, Veracruz. The hydrocarbonoclastic (HCT) bacteria and fungi were incorporated into a soil polluted with 25 000 mg kg(-1) of crude petroleum in which bean (Phaseolus vulgaris L.) and corn (Zea mays L.) were sown. The removal of the pollutant as a result of the interaction among bean, corn, HCT bacteria and fungi was studied. Three greenhouse experiments were set up with bean, corn and bean-corn association, arranged in a completely randomized experimental design. Each experiment had six treatments: a) bacteria + plant, b) bacteria + fungi + plant, c) no microorganisms + plant, d) bacteria without plant, e) bacteria + fungi without plant, and f) no microorganisms, without plant. Each treatment had six replicates. Microbial populations and the removal of petroleum were evaluated 28 and 48 days after sowing. The results showed the highest populations of hydrocarbonoclastic bacteria (6.03 x 10(8)) and fungi (2.75 x 10(5)) in the rhizosphere of bean-corn + bacteria + fungi 48 days after sowing. The rhizosphere of corn inoculated with hydrocarbonoclastic bacteria showed the highest removal rate of total petroleum hydrocarbons 48 days after sowing. The importance of hydrocarbonoclastic microorganisms in the rhizosphere for removal of petroleum in contaminated soils was demonstrated in the present study.