Abstract:
The rhizosphere is one of the most dynamic areas of biodegradation in soil because of the
interaction among microbiota, plant roots and ecosystem productivity processes. In this study,
heterotrophic microbial communities and endophytic nitrogen-fixing bacteria associated with the
rhizosphere of the plant species Xanthosoma daguense and Oplismenus burmannii in subandine
forest soils at the Colombian coffee-growing region were characterized with respect to their
ability to degrade carbon substrates. In this preliminary study we analyzed the rhizosphere of
two plant species variation in microbial community functional diversity using sole-carbon-
source utilization profiles. The metabolic capacity of heterotrophic microbial communities was
evaluated for 31 carbon substrates on Biolog EcoPlatesTM grouped as carbohydrates, amino
acids, carboxylic acids, amines, carbon phosphates and carbon complex. For the isolation of
endophytic diazotrophs, the semisolid media LGI, LGI-P, NFb and JNFb were used and the
ability to degrade 47 types of substrates was evaluated using Vitek 2 Compact'. The
heterotrophic microbial community associated with the rhizosphere of X. daguense and O.
burmannii exhibited a functional diversity of 90% and 68% respectively. Cluster analysis for the
nitrogen-fixing bacterial isolates allowed separation of colonies based on the use of substrates,
confirming metabolic diversity. These data demonstrate the differential metabolic capacity of the
rhizosphere of X. daguense and O. burmannii to favor growing microbes in the rizhosphere which is important in the potential contribution of microbial communities to the matter
decomposition in this type of ecosystem.
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