Hypersaline environments as natural sources of microbes with potential applications in biotechnology: The case of solar evaporation systems to produce salt in Alicante County (Spain)

Abstract

Extremophilic microbes show a unique metabolism due to the adaptations they display to deal with extreme environmental parameters characterizing the extreme ecosystems that they inhabit (high salt concentration, high temperatures, and extreme pH values, high exposure to solar radiation etc.). Halophilic microorganisms characterised and isolated from saltmarshes, brines, salted ponds, salty lagoons etc. have recently attracted attention due to their potential biotechnological applications (as whole cells used for different purposes like wastewater treatments, or their biomolecules: enzymes, antibiotics, carotenoids, bioplastics). Alicante county (southeast of Spain) accounts for a significant number of salty environments like coastal or inland salty ponds from where sodium chloride (NaCl)is obtained, marshes, salty lagoons, etc. The best system characterised so far from a microbiological point of view is "Salinas de Santa Pola", also termed "Salinas Bras del Port". However, there are many other salty environments to be explored, like the natural park of Torrevieja and la Mata lagoons, salty lagoon located in Calpe city or inland salted ponds like those located in the northwest of the county. This review summarises the most relevant biotechnological applications of halophilic microbes described up to now. In addition, special attention is focused on ecosystems such as the lagoons of Torrevieja or inland salt marshes as natural environments whose microbial biodiversity is worthy of being studied in search of new strains and species with the aim to analyze their potential biotechnological applications (pharmaceutical, food industry, biomedicine, etc.).

Keywords: Bacterioruberin; Enzymes; Haloarchaea; Halobacteria; Halocins; Halovirus; Polyhydroxyalkanoates.

Graphical abstract

Fig. 1

A. Satellite image showing the salt lagoons of Torrevieja and La Mata (https://www.google.es/maps/search/parque±laguna±torrevieja/@38.0057332,−0.7386368,10,859 m/data=!3m2!1e3!4b1). The lagoon on the right side corresponds to the heater, which is directly connected to the Mediterranean Sea; while the lagoon on the left corresponds to the precipitation ponds. B. Worker tacking samples from the center of the lagoon for quality monitoring and research.

Fig. 2

Summary of the current classification of Archaea domain. Green color highlights the groups that constitute the main microbial populations in extrema halophilic environments like salted ponds, marshes, and coastal lagoons (Adapted from Gupta et al., 2016). TACK is a group of archaea acronym or Thaumarchaeota, Aigarchaeota, Thermoproteota and Korarchaeota, the first groups discovered. DPANN is a superphylum of Archaea first proposed in 2013 (They are known as nanoarchaea or ultra-small archaea due to their smaller size (nanometric) compared to other archaea).