editorial biodesert: exploring and exploiting the...

EditorialBIODESERT: Exploring and Exploiting the Microbial Resourceof Hot and Cold Deserts

Ameur Cherif,1 George Tsiamis,2 Stéphane Compant,3 and Sara Borin4

1University of Manouba, Biotechnology and Bio-Geo Resources Valorization (LR11-ES31), Higher Institute for Biotechnology,BiotechPole Sidi Thabet, 2020 Ariana, Tunisia2Department of Environmental and Natural Resources Management, University of Patras, 2 Seferi Street, 30100 Agrinio, Greece3Bioresources Unit, Health & Environment Department, AIT Austrian Institute of Technology GmbH, 3430 Tulln, Austria4Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy

Correspondence should be addressed to Ameur Cherif; [email protected]

Received 15 February 2015; Accepted 15 February 2015

Copyright © 2015 Ameur Cherif et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Deserts are generally regarded as lifeless and inhospitableecosystems despite the general awareness of extremophilicmicroorganisms. An amazing microbial diversity and a hugebiotechnological potential were unraveled during the lastdecade using molecular approaches. Hot and cold desertswere shown to host peculiar microbial assemblages able tocope with hostile environment and/or to rapidly adapt tochanging conditions. This adaptation is inferred to partic-ular community structure behavior and specific metaboliccapacities allowing cells to overcome water stress, fluctuatingtemperature, and high salinity. Therefore, such microbescould constitute a source of novel metabolites, biomolecules,and enzymes potentially useful for environmental biotech-nologies.With the global climate change, the aridification andcreeping desertification that constitute a worldwide seriousthreat directly affecting agriculture and crop production, andthe growing food demands, desert microorganisms couldhold the key for green biotechnology and future applicationsinto soil bioreclamation and plant growth promotion forvulnerable regions across the world.

This special issue was focused on the desert microbialresourcemanagement (MRM) andhow to explore and exploitthese resources from hot and cold deserts as well as fromarid areas. Aspects of this MRM concept are included inthis special issue and they are highlighting (a) the microbialdiversity and community structure behavior in desert envi-ronments and the identification of novel extremophiles, (b)the influence of the biotic and abiotic factors on microbial

communities shape and dynamic and the functional net-working including mechanism of adaptation and plant-microbes interaction under extreme or changing conditions,and (c) potential and case applications of desert microbesand/or mixed cultures, such as in soil bioreclamation,reverse-desertification, agriculture, and biomining.

This special issue contains one review and eight researcharticles that address the three main aspects indicated above.The paper of A. Jaouani et al., entitled “Diversity and Enzy-matic Profiling of HalotolerantMicromycetes from Sebkha ElMelah, a Saharan Salt Flat in Southern Tunisia,” reported theisolation of 21 alkali-halotolerantAscomycetes assigned to the6 genera Cladosporium, Alternaria, Aspergillus, Penicillium,Ulocladium, and Engyodontium, basing on morphologicaland molecular markers. Beside their salt and pH tolerance,these saline-system fungi were shown to resist to oxidativestress and low temperature and to produce extremozymes,namely, cellulase, amylase, protease, lipase, and laccase, activein high salt concentrations, which highlight their biotechno-logical potential. The paper authored by M. del C. Montero-Calasanz et al., “Geodermatophilus poikilotrophi sp. nov.: AMultitolerant Actinomycete Isolated from Dolomitic Marble,”described a new species within the genus Geodermatophilus.Strain G18T, isolated from site near the Namib Desert,is characterized by its resistance to heavy metals, metal-loids, hydrogen peroxide, desiccation and ionizing, and UV-radiations. Even though 16S rRNA sequence of strain G18Tshowed 99% similarity with other Geodermatophilus species,

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015, Article ID 289457, 2 pageshttp://dx.doi.org/10.1155/2015/289457

2 BioMed Research International

its taxonomic position and species definition was inferredbasing onpolyphasic approach and itsmultitolerance towardsenvironmental stresses, justifying the original given epithet“poikilotrophi.”

Four papers were dedicated to the ecological driversthat shape microbial communities and functionalities. Anice example of “cold desert” is presented by S. Ciccazzo etal., “Safe-site Effects on Rhizosphere Bacterial Communitiesin a High-Altitude Alpine Environment.” In this work, theauthors investigated rhizobacterial communities associatedwith floristic consortia in different safe-sites located indeglaciated terrain. Using DGGE and ARISA, they demon-strated a clear correlation between soil maturation andbacterial diversity and a plant-specific effect leading to theselection of specific rhizobacterial communities by the pio-neer plants. Another model ecosystem was investigated by R.Ferjani et al., in the paper “The Date Palm Tree RhizosphereIs a Niche for Plant Growth Promoting Bacteria in the OasisEcosystem.” The work focused on the characterization ofthe bacterial communities in the soil fractions associatedwith the root system of date palms cultivated in sevenoases in Tunisia using culture-independent and dependentapproaches. It was shown that the date palm rhizospherebacterial communities were rather complex and correlatewith geoclimatic and macroecological factors along a north-south aridity transect. However, with the wide diversity ofcultivable strains detected, interesting common features ofplant growth promoting (PGP) activity and abiotic stressresistance were detected. The authors concluded that palmroot system and rhizosphere soil represent a reservoir of PGPbacteria involved in the regulation of plant homeostasis. Thethird example of plant-microbe interaction is the paper byI. Nouioui et al., in which they demonstrated, as written inthe title, the “Absence of Cospeciation between the Uncul-tured FrankiaMicrosymbionts and the Disjunct ActinorhizalCoriaria Species.” The investigation was achieved on fiveCoriaria host species sampled from sites covering the fullgeographical range of the genus (Morocco, France, NewZealand, Pakistan, Japan, and Mexico). The reported find-ings argue that Frankia, the nitrogen-fixing actinobacteriamicrosymbionts, have not evolved jointly with their hostplants and had probably dispersed globally as a proto-Frankia, a free living nonsymbiotic ancestor. The authorshypothesized also that cospeciation may have occurred butsubsequently lost after bacteriamixing andfitness selection inthe presence of indigenous symbionts. Frankia sp. was furtherinvestigated in terms of nitrogen fixation under differentoxygen tensions. This work authored by F. Ghodhbane-Gtariet al. was conducted on the actinorhizal plant Casuarina andits compatible Frankia sp. strain CcI3. By studying the growthof the strain, vesicle production, and several genes expression,the authors confirmed the correlation between the biomassand the vesicle production with elevated oxygen tension. Itwas also shown that oxygen levels influenced nitrogenaseinduction and that Frankia protects nitrogenase by the use ofmultiple mechanisms including the vesicle-hopanoid barrierand increased respiratory protection. Clearly, the microbialassemblages selected by the plant roots in desert and arid soilsare shaped by the ecological biotic and abiotic drivers butwith

the prerequisite of providing rhizosphere services and specificfunctionalities.

Biotechnological potential and applications of desertmicrobes have been reported in three papers. In one, A.Khessairi et al. described a novel efficient pentachlorophenol-(PCP-) degrading halotolerant actinobacterium, Janibactersp. FAS23. The strain was isolated from Sebkha El Naoual, asaline ecosystem in southern Tunisia. Using HPLC analysis,FAS23 was shown to be able to degrade high concentrationof PCP (up to 300mg/l) and to tolerate salt fluctuation. PCPdegradation was further enhanced in the presence of glucoseand nonionic surfactant tween 80.The strain is considered asa candidate for PCP bioremediation in polluted soils in aridareas. In another paper authored by O. Selama et al., the iso-lation of haloalkalitolerant and haloalkaliphilic bacteria fromAlgerian Sahara Desert soil was reported. Thirteen selectedisolates, mainly filamentous Actinobacteria, were screenedphenotypically for antibacterial, antifungal, and enzymaticactivities and by PCR for putative antitumor compoundsgenes. The isolates were assigned to the genera Streptomyces,Nocardiopsis, Pseudonocardia, Actinopolyspora, and Nocar-dia, with this latter constituting possibly a new branch intheActinomycetales order. Beside secreted extremozymes andbioactives, several isolates showed antitumorigenic potential.Another paper presented in this special issue is a review arti-cle nicely written by A. Azua-Bustos and C. Gonzalez-Silva,who focused on the Atacama Desert microbes and their cur-rent biotechnological applications. A large-scale applicationin Chile is the copper bioleaching or biomining mediated byindigenous halotolerant and acidophilic chemolithotrophicbacteria likeAcidithiobacillus ferrooxidans andAcidithiobacil-lus thiooxidans. Other potential applications in arsenic biore-mediation and in biomedicine, including the discovery ofnew antibiotics, antioxidant, antifungal, and immunosup-pressive compounds, were cited. The authors reported alsoapplication from eukaryotic microorganism as in the caseof the halophilic biflagellate unicellular green alga Dunaliellathat produce beta-carotene.

Definitely, desert environments represent a tremendousreservoir where more efforts, relying not only on metage-nomics but also on culturomics, should be dedicated tounravel the hidden potential. The second decade for desertbiotechnology has just begun.

Acknowledgments

We thank the authors of the submitted papers for theircontribution. The preparation of this special issue wouldnot have been possible without the generous support anddedication of experts who evaluated the papers submitted.

Ameur CherifGeorge Tsiamis

Stephane CompantSara Borin

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