Survival of Filamentous Fungi in Hypersaline Dead Sea Water

Abstract

A variety of filamentous fungi have recently been isolated from the Dead Sea (340 g/L total dissolved salts). To assess the extent to which such fungi can survive for prolonged periods in Dead Sea water, we examined the survival of both spores and mycelia in undiluted Dead Sea water and in Dead Sea water diluted to different degrees with distilled water. Mycelia of Aspergillus versicolor and Chaetomium globosum strains isolated from the Dead Sea remained viable for up to 8 weeks in undiluted Dead Sea water. Four Dead Sea isolates (A. versicolor, Eurotium herbariorum, Gymnascella marismortui, and C. globosum) retained their viability in Dead Sea water diluted to 80% during the 12 weeks of the experiment. Mycelia of all species survived for the full term of the experiment in Dead Sea water diluted to 50% and 10% of its original salinity. Comparison of the survival of Dead Sea species and closely related isolates obtained from other locations showed prolonged viability of the strains obtained from the Dead Sea. Spores of isolates obtained from the terrestrial shore of the Dead Sea generally proved less tolerant to suspension in undiluted Dead Sea water than spores of species isolated from the water column. Spores of the species isolated from the control sites had lost their viability in undiluted Dead Sea water within 12 weeks. However, with the exception of Emericella spores, which showed poor survival, a substantial fraction of the spores of Dead Sea fungal isolates remained viable for that period. The difference in survival rate between spores and mycelia of isolates of the same species points to the existence of adapted halotolerant and/or halophilic fungi in the Dead Sea.

The culturable mycobiota of a Mediterranean marine site after an oil spill: isolation, identification and potential application in bioremediation

“…Among the most abundant water species, S. racemosum, A. tenuissima and C. globosum have already been reported in marine environment (Baakza et al, 2004;Kis-Papo et al, 2003;Sepcic et al 2011), but this is the first record from oil-contaminated seawater. S. racemosum is well known for its ability to oxidize aromatic compounds as benzo [a]pyrene (Cerniglia, 1997).…”

Evolution of genomic diversity and sex at extreme environments: Fungal life under hypersaline Dead Sea stress

“…They were less tolerant to incubation in undiluted DSW than the isolates obtained from the sea brines. On the other hand, in diluted DSW (80%), simulating a diluted upper layer formed after rains and flooding, spores of shore isolates (DSTS) remained viable to the same extent as the DSW isolates (21).…”

“…Most of the species are sporadic or rare, but a spatiotemporal study revealed a steady species core including Aspergillus versicolor and Eurotium herbariorum (18). Some of the fungi isolated from the Dead Sea grew in DSW that was diluted to half its original salinity, and their spores remained viable after incubation in undiluted DSW for extended periods (21). Live mycelium of nine fungal species, including Eurotium amstelodami, E. herbariorum, and Eurotium rubrum, were found growing on driftwood that submerged near the aquatic shore (20,22).…”

A First Record of Obligate Halophilic Aspergilli from the Dead Sea

“…This unique ionic composition makes it hostile to microorganisms and could be responsible for the paucity in the diversity of the Dead Sea biota [5,6]. Microbes that inhabit high-salt environments are adapted to high levels of ions, as well as to low a w , and are described as halophilic or halotolerant, while the term xerophilic or xerotolerant is restricted to describing those organisms growing at a w values imposed by other than inorganic ions [7].…”

“…A number of filamentous fungi have been isolated from the Dead Sea [3,5,6]; however, only the species of Gymnascella marismortui has been reported as a true halophile, having an absolute requirement of salt for growth [5,8].…”