Isolation, Identification and Characterization of Two Aluminum-Tolerant Fungi from Acidic Red Soil

Abstract

Acidic red soil from a forest in Jiangxi Province was selected to isolate aluminum (Al)-resistant microbes, from which eight fungi were isolated. Two strains (S4 and S7) were found to be extremely tolerant to Al concentrations of up to 550 mmol L(-1) and could grow at low pH levels (3.20-3.11). Morphological and 26S rDNA sequence analyses indicated that strain S4 belonged to Eupenicillium, while strain S7 was an unclassified Trichocomaceae. Further investigation showed that both strains were endowed with the ability to resist Al; strain S4 accumulated such a substantial amount of Al that its growth was limited to a larger extent than strain S7. The lower amounts of Al adsorbed in the mycelium and the much larger amounts of Al retained in the medium, in addition to the color change of the culture solution, implied that these two strains may resist Al by preventing Al from entering the cell and by chelating Al by secreting unique metabolites outside of the cell.

Keywords: Al tolerance; Al tolerant microbe; Aluminum toxicity; Fungi.

Fig. 1

Spore morphology of strains S4 and S7

Fig. 2

Acquisition of 26S rDNA sequences of S4 and S7 strains and the phylogenetic analysis with other strains (Phylogenetic tree was evaluated by bootstrap analysis of the neighbor-joining method with 1000 resamplings using MEGA 5.0)

Fig. 3

The growth condition of strains S4 and S7 under different concentrations of Al and different pH levels

Fig. 4

Al absorption of strains S4 and S7 (left) and hematoxylin staining of the colonies (right). a, b indicated strain S4 without/with hematoxylin and c, d indicated strain S7 without/with hematoxylin

Fig. 5

The dry weight of strains S4 and S7 after 5 days suspension culture at different concentrations of Al³⁺

Fig. 6

The growth conditions of strains S4 and S7 in liquid medium containing different Al³⁺ at different incubation time