A novel, cheap and easy preparing selective medium for isolation of Pythium species

Isolation of Pythium and Globisporangium (Chromista, Oomycota) from their natural sources is very difficult due to the heavy contamination with other microbes, which hinders obtaining them in pure form. This study aims to develop a new, cheap and safe selective medium to isolate Pythium and Globisporangium species from their natural sources, despite the previous presence of more than 3 types of selective media including: VP₃ (Vancomycin + PCNB + Penicillin + Pimaricin), NARM (Nystatin + Ampicillin + Rifampicin + Miconazole), and NARF (Nystatin + Ampicillin + Rifampicin + Fluazinam) used to isolate Oomycota. The elevated expense of antibiotics, along with alerts regarding potential contamination, toxicity, and tumor proliferation, renders them undesirable. Safe and inexpensive antibiotics from pharmaceutical sources were used with fixed formulations and concentrations. A selective medium was developed, called FANS (Fluconazole + Ampicillin + Nystatin + Sulbactam) with the following concentrations (1200 mg + 500 mg + 100,000 IU + 250 mg) respectively/L Corn Meal Agar promotes only the growth and formation of reproductive structures of Pythium and Globisporangium. On the other hand, these antibiotics completely inhibited the growth of other contaminated fungi and bacteria. Mycelial growth, zoospore formation, and oospore production for (Pythium aphanidermatum, Pythium oligandrum, and Globisporangium ultimum var. ultimum) were highest in FANS, followed by NARM, then NARF, while VP₃ gave the lowest results compared to the control sample. It can be concluded that the use of FANS selective medium made the process of Pythium isolation easier, safer, and less expensive for worldwide researchers especially in developing and low-income countries.