An appraisal on saprophytic and function microbial communities associated to the carnivorous plant Drosera latifolia (Eichler) (Droseraceae)

Abstract

The carnivorous plant Drosera latifolia (Eichler) Gonella & Rivadavia (Droseraceae) colonizes humid, acidic, and oligotrophic soils, relying on several strategies to get nutrients for growth. Besides predation, microbial functional groups are critical for carbon and nutrient cycling in the rhizosphere, but there is no information on how they interact in the (endo) rhizosphere of Drosera. We assessed the occurrence of heterotrophic bacteria, saprophytic fungi, actinobacteria and pseudomonads and correlated them with microbial functional groups (cellulolytic, amylolytic, nitrogen-fixing and proteolytic bacteria) in the rhizosphere and endorhizosphere of Drosera collected during the winter and summer in two sites of natural occurrence (Rio Verde, SP and Joaquim Murtinho, PR). In each site, five samples of plants occurring on three substrates were taken: moss, peat, and sand. The population of heterotrophic bacteria correlated positively with saprophytic fungi, nitrogen-fixing bacteria that use malate as C source and amylolytic populations. The fungi showed a positive correlation with amylolytics, cellulolytics and both nitrogen-fixing bacterial groups. The correlation between the Pseudomonas fluorescens and amylolytic populations was negative, as well as between P. fluorescens and nitrogen-fixing bacteria that use malate as carbon source. Although Drosera nutrition partially relies on the capture of small animals, mainly insects, plants also interact synergistically with functional microorganisms associated to their rhizosphere, which could therefore contribute to the nutritional requirements under oligotrophic environments, helping the plant to cope with survival in low-fertility soils.