Aspergillus niger Environmental Isolates

Sixteen Aspergillus niger (A. niger) strains were isolated from different types of soils (samples 1, 3, 4, 7, 8, 10, 12–l4), coal dust (sample 2), stream sediments (samples 5 and 6), an ash layer (sample 11), a tailing pond (samples 9 and 15) and a surface of artificial adamite (sample 16) (Figure 1). The samples from all solid substrates were taken from three places at each site. Then in laboratory by mixing an average sample was prepared and analysed. From the surface of artificial adamite was A. niger isolated by using a SWABS swab (1660, Dispolab Brno, Czechia) and subsequent cultivated on Sabouraud Dextrose Agar (M063), HiMedia Labs., Mumbai, India). The chemical characteristics of the localities and substrates from which A. niger strains were isolated are shown in Table 1.

Map showing the sampling localities in Slovakia and the Czechia.

Aspergillus niger environmental isolates obtained from different type of soils and solid sources and its chemical characteristics.

The metallic element composition of the samples from the Banská Štiavnica—Šobov, Pezinok, Nováky, and Smolník localities were analysed by the EL spol. Ltd. accredited test labs in Spišská Nová Ves (Slovakia). Samples from the Poproč, Zemianske Kostol’any, and Slovinky localities were analysed for their metal content at ACME Analytical Laboratories Ltd. (Vancouver, Canada) by ICP-ES or ICP-MS (Šimonovičová et al., 2019). Persistent toxic substances in the Ostrava Lagoons locality were analysed in sludge samples (mg/kg of dry weight) using several methods. XRF technology—X-ray fluorescence spectrometry with high sensitivity on the S8 TIGER instrument (Bruker Co., United States) was used for the analysis of metal and metalloid residues. Organic pollution analyses were performed at ALS Czech Republic, Ltd. (a testing laboratory accredited according to ČSN (Czech National Standard) EN ISO/IEC 17025:2005).

All strains were isolated from mixed cultures of fungi by the dilution plate method on SDA (Sabouraud Dextrose Agar, FyHimedia Laboratories, Mumbai, India) at a laboratory temperature of 25°C for 5–7 days (Šimonovičová et al., 2013, 2017, 2019). All isolates were assigned to A. niger according to molecular analyses and according to the name of the locality, as shown in Table 1. All strains are deposited on SDA in the collection of filamentous fungi in the Department of Soil Science at the Faculty of Natural Sciences, Comenius University in Bratislava (Slovakia). The ITS sequences of the Aspergillus niger isolates were deposited in GenBank under accession numbers {"type":"entrez-nucleotide","attrs":{"text":"MW739953","term_id":"2006086633","term_text":"MW739953"}}MW739953-{"type":"entrez-nucleotide","attrs":{"text":"MW739968","term_id":"2006086661","term_text":"MW739968"}}MW739968.