Toxicity of β-(1→3,1→6)-ᴅ-glucans produced by Diaporthe sp. endophytes on Metarhizium anisopliae (Metschnikoff) Sorokin assessed by conidia germination speed parameter

Abstract

Previously, our study reported that β-(1→3,1→6)-ᴅ-glucans produced by endophytes Diaporthe sp. G27-60 and G65-65 (GenBank accession codes JF766998 and JF767007, respectively) are promising antiproliferative agents against human breast carcinoma (MCF-7) and hepatocellular carcinoma (HepG2-C3A) cells. However, effects of Diaporthe exopolysaccharides on eukaryotic healthy cells are not described in current literature. The fungus Metarhizium anisopliae has been employed as teste-system to evaluate the toxicity of pharmaceutical and agricultural-interest substances, considering, among other parameters, conidia germination speed. The current study aimed to verify the effect of different concentrations of Diaporthe β-glucans on the germination speed of M. anisopliae. Conidia were incubated with β-glucans treatments (50, 200 and 400 μg/mL) at 28 ºC, sampled throughout 24 h and analyzed by light microscopy. At the end of 24 h of incubation, the amount of germinated conidia was ≈99% for controls and ranged from 97.7 to 98.6% for treatments. Bayesian analysis indicated that Diaporthe glucans had no toxicity on M. anisopliae and the curve of germination occurred as expected for this fungal strain. Considering the validity of filamentous fungi as model systems, these results are important data about the toxicity of these endophytic EPS on healthy cells and may be associated with previous results obtained for these polymers against tumor cells. Keywords: bayesian analysis, conidia germination, endophytic fungi, exopolysaccharide, fungal model-system.