Inner Leaf Gel of Aloe striata Induces Adhesion-Reducing Morphological Hyphal Aberrations

Abstract

Fungi, particularly molds that are cosmopolitan in soils, are frequent etiologic agents of opportunistic mycoses. Members of the Fusarium solani and Fusarium oxysporum species complexes are the most commonly implicated etiologic agents of opportunistic fusarial infections in mammals, while Paecilomyces variotii is one of the most frequently encountered Paecilomyces species in human infections. Prevention and treatment of these mycoses are problematic because available antimycotics are limited and often have toxic side effects. Popular folk medicines, such as the inner leaf gel from Aloe spp., offer potential sources for novel antimycotic compounds. To screen for antifungal properties of Aloe striata, we treated conidia of three strains each of F. solani, F. oxysporum, and P. variotii with homogenized and filtered inner leaf gel. Exposure to gel homogenates caused minimal inhibition of conidial germination in tested strains. However, it significantly increased the frequency of hyphal aberrations characterized by increased hyphal diameters that resulted in intervals of non-parallel cell walls. Non-parallel cell walls ostensibly reduce total hyphal surface area available for adhesion. We found a significant decrease in the ability of aberrated P. variotii hyphae to remain adhered to microscope slides after repeated washing with reverse osmosis water. Our results suggest that treatment with A. striata contributes to a decrease in the adhesion frequency of tested P. variotii strains.

Keywords: Aloe; Aloe striata; Fusarium; Paecilomyces; aberrations; adhesion; antifungal; germination.

Figure 1

Examples of the various fungal morphologies encountered in germination and adhesion assays. (A) Reverse osmosis water (ROH₂O) (control) treated fungi; (B–E) Different morphologies observed in A. striata treated Pv19; (B) swollen with parallel cell walls (SP), (C) swollen with non-parallel cell walls in the sub-conidial hyphal region (SNPSC), (D) swollen with non-parallel cell walls up to the midpoint hyphal region (SNPM), and (E) swollen with non-parallel cell walls throughout the hyphal length (SNPL). Arrows point to locations on hyphae where non-parallel cell walls are present.

Figure 2

Effect of A. striata inner leaf gel on the aberration frequency of selected F. oxysporum (Fo69), F. solani (Fs02), and P. variotii (Pv19) strains in repeated germination assays. * Indicates statistical significance, error bars represent standard error of the mean, n = 200, p-value < 0.01.

Figure 3

Average percent of adhered fungi in adhesion assays. (A) Average total percentage of adhered P. variotii strains (Pv19, Pv06, and Pv23) after treatment with A. striata (As) and reverse osmosis water (RO water) in adhesion assays that were repeated on three separate days with three replicates per day; (B) Average total percentage of the total adhered fungi per morphotypes (non-aberrated (NA), SP, SNPM, SNPL, and SNPSC) per P. variotii strain. * Indicates p-value < 0.001.

Figure 3

Average percent of adhered fungi in adhesion assays. (A) Average total percentage of adhered P. variotii strains (Pv19, Pv06, and Pv23) after treatment with A. striata (As) and reverse osmosis water (RO water) in adhesion assays that were repeated on three separate days with three replicates per day; (B) Average total percentage of the total adhered fungi per morphotypes (non-aberrated (NA), SP, SNPM, SNPL, and SNPSC) per P. variotii strain. * Indicates p-value < 0.001.