RESUMEN
The Atacama Desert is the oldest and driest desert on Earth, encompassing great temperature variations, high ultraviolet radiation, drought, and high salinity, making it ideal for studying the limits of life and resistance strategies. It is also known for harboring a great biodiversity of adapted life forms. While desertification is increasing as a result of climate change and human activities, it is necessary to optimize soil and water usage, where stress-resistant crops are possible solutions. As many studies have revealed the great impact of the rhizobiome on plant growth efficiency and resistance to abiotic stress, we set up to explore the rhizospheric soils of Suaeda foliosa and Distichlis spicata desert plants. By culturing these soils and using 16S rRNA amplicon sequencing, we address community taxonomy composition dynamics, stability through time, and the ability to promote lettuce plant growth. The rhizospheric soil communities were dominated by the families Pseudomonadaceae, Bacillaceae, and Planococcaceae for S. foliosa and Porphyromonadaceae and Haloferacaceae for D. spicata. Nonetheless, the cultures were completely dominated by the Enterobacteriaceae family (up to 98%). Effectively, lettuce plants supplemented with the cultures showed greater size and biomass accumulation. We identified 12 candidates that could be responsible for these outcomes, of which 5 (Enterococcus, Pseudomonas, Klebsiella, Paenisporosarcina, and Ammoniphilus) were part of the built co-occurrence network. We aim to contribute to the efforts to characterize the microbial communities as key for the plant's survival in extreme environments and as a possible source of consortia with plant growth promotion traits aimed at agricultural applications.IMPORTANCEThe current scenario of climate change and desertification represents a series of incoming challenges for all living organisms. As the human population grows rapidly, so does the rising demand for food and natural resources; thus, it is necessary to make agriculture more efficient by optimizing soil and water usage, thus ensuring future food supplies. Particularly, the Atacama Desert (northern Chile) is considered the most arid place on Earth as a consequence of geological and climatic characteristics, such as the naturally low precipitation patterns and high temperatures, which makes it an ideal place to carry out research that seeks to aid agriculture in future conditions that are predicted to resemble these scenarios. Our main interest lies in utilizing microorganism consortia from plants thriving under extreme conditions, aiming to promote plant growth, improve crops, and render "unsuitable" soils farmable.
Asunto(s)
Bacterias , Clima Desértico , ARN Ribosómico 16S , Rizosfera , Microbiología del Suelo , Bacterias/clasificación , Bacterias/genética , Bacterias/aislamiento & purificación , Bacterias/crecimiento & desarrollo , ARN Ribosómico 16S/genética , Desarrollo de la Planta , Lactuca/microbiología , Lactuca/crecimiento & desarrollo , Microbiota , Suelo/química , Biodiversidad , Chenopodiaceae/microbiología , Chenopodiaceae/crecimiento & desarrolloRESUMEN
The role of microorganisms in litter degradation in arid and semi-arid zones, where soil and water salinization is one of the main factors limiting carbon turnover and decay, remains obscure. Heterostachys ritteriana (Amaranthaceae), a halophyte shrub growing in arid environments such as "Salinas Grandes" (Córdoba, Argentina), appears to be the main source of organic matter in the area. Little is known regarding the microorganisms associated with H. ritteriana, although they are a potential source of enzymes such as cellulolytic ones, which might be important in biotechnological fields such as bioethanol production using ionic liquids. In the present study, by studying the microbiota growing on H. ritteriana leaf litter in "Salinas Grandes," we isolated the cellulolytic fungus Fusarium equiseti LPSC 1166, which grew and degraded leaf litter under salt stress. The growth of this fungus was a function of the C substrate and the presence of NaCl. Although in vitro the fungus used both soluble and polymeric compounds from H. ritteriana litter and synthesized extracellular ß-1,4 endoglucanases, its activity was reduced by 10% NaCl. Based on these results, F. equiseti LPSC 1166 can be described as a halotolerant cellulolytic fungus most probably playing a key role in the decay of H. ritteriana leaf litter in "Salinas Grandes."
Asunto(s)
Chenopodiaceae/microbiología , Fusarium/metabolismo , Hojas de la Planta/microbiología , Biodegradación Ambiental , Celulosa/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Fusarium/enzimología , Fusarium/genética , Glicósido Hidrolasas/genética , Glicósido Hidrolasas/metabolismo , Cloruro de Sodio/metabolismoRESUMEN
Halophytes accumulate large amounts of salt in their tissues, and thus are susceptible to colonization by halotolerant and halophilic microorganisms that might be relevant for the growth and development of the plant. Here, the study of 814 cultured strains and 14,189 sequences obtained by 454 pyrosequencing were combined in order to evaluate the presence, abundance and diversity of halophilic, endophytic and epiphytic microorganisms in the phytosphere of leaves of members of the subfamily Salicornioideae from five locations in Spain and Chile. Cultures were screened by the tandem approach of MALDI-TOF/MS and 16S rRNA gene sequencing. In addition, differential centrifugation was used to enrich endophytes for further DNA isolation, 16S rRNA gene amplification and 454 pyrosequencing. Culturable and non-culturable data showed strong agreement with a predominance of Proteobacteria, Firmicutes and Actinobacteria. The most abundant isolates corresponded to close relatives of the species Chromohalobacter canadensis and Salinicola halophilus that comprised nearly 60% of all isolates and were present in all plants. Up to 66% of the diversity retrieved by pyrosequencing could be brought into pure cultures and the community structures were highly dependent on the compartment where the microorganisms thrived (plant surface or internal tissues).