Characterization of hypersaline Oklahoma native microalgae cultivated in flowback and produced water: growth profile and contaminant removal.

This work explores the potential of three hypersaline native microalgae strains from Oklahoma, Geitlerinema carotinosum, Pseudanabaena sp., and Picochlorum oklahomensis, for simultaneous treatment of flowback (FW) and produced wastewater (PW) and the production of algal biomass. The quality of wastewater before and after treatment with these microalgae strains was evaluated and a characterization of algal biomass in terms of moisture, volatile matter, fixed carbon, and ash contents was assessed. The experimental results indicated how all the microalgae strains were able to grow in both FW and PW, revealing their potential for wastewater treatment. Although algal biomass production was limited by nutrient availability both in PW and FW, a maximum biomass concentration higher than 1.35 g L-1 were achieved by the three strains in two of the PWs and one of the FWs tested, with Pseudanabaena sp. reaching nearly 2 g L-1. Interestingly, higher specific growth rates were obtained by the two cyanobacteria strains G. carotinosum and Pseudanabaena sp. when cultivated in both PW and FW, compared to P. oklahomensis. The harvested algal biomass contained a significant amount of energy, even though it was significantly reduced by the very high salt content. The energy content fell within the recommended range of 16-17 MJ kg-1 for biomass as feedstock for biofuels. The algal treatment resulted in the complete removal of ammonia from the wastewater and a significant reduction in contaminants, such as nitrate, phosphate, boron, and micronutrients like zinc, manganese, and iron.

Arbuscular mycorrhizal fungi impact the production of alkannin/shikonin and their derivatives in Alkanna tinctoria Tausch. grown in semi-hydroponic and pot cultivation systems.

Introduction: Alkanna tinctoria Tausch. is a medicinal plant well-known to produce important therapeutic compounds, such as alkannin/shikonin and their derivatives (A/Sd). It associates with arbuscular mycorrhizal fungi (AMF), which are known, amongst others beneficial effects, to modulate the plant secondary metabolites (SMs) biosynthesis. However, to the best of our knowledge, no study on the effects of AMF strains on the growth and production of A/Sd in A. tinctoria has been reported in the literature. Methods: Here, three experiments were conducted. In Experiment 1, plants were associated with the GINCO strain Rhizophagus irregularis MUCL 41833 and, in Experiment 2, with two strains of GINCO (R. irregularis MUCL 41833 and Rhizophagus aggregatus MUCL 49408) and two native strains isolated from wild growing A. tinctoria (R. irregularis and Septoglomus viscosum) and were grown in a semi-hydroponic (S-H) cultivation system. Plants were harvested after 9 and 37 days in Experiment 1 and 9 days in Experiment 2. In Experiment 3, plants were associated with the two native AMF strains and with R. irregularis MUCL 41833 and were grown for 85 days in pots under greenhouse conditions. Quantification and identification of A/Sd were performed by HPLC-PDA and by HPLC-HRMS/MS, respectively. LePGT1, LePGT2, and GHQH genes involved in the A/Sd biosynthesis were analyzed through RT-qPCR. Results: In Experiment 1, no significant differences were noticed in the production of A/Sd. Conversely, in Experiments 2 and 3, plants associated with the native AMF R. irregularis had the highest content of total A/Sd expressed as shikonin equivalent. In Experiment 1, a significantly higher relative expression of both LePGT1 and LePGT2 was observed in plants inoculated with R. irregularis MUCL 41833 compared with control plants after 37 days in the S-H cultivation system. Similarly, a significantly higher relative expression of LePGT2 in plants inoculated with R. irregularis MUCL 41833 was noticed after 9 versus 37 days in the S-H cultivation system. In Experiment 2, a significant lower relative expression of LePGT2 was observed in native AMF R. irregularis inoculated plants compared to the control. Discussion: Overall, our study showed that the native R. irregularis strain increased A/Sd production in A. tinctoria regardless of the growing system used, further suggesting that the inoculation of native/best performing AMF is a promising method to improve the production of important SMs.

Selected indigenous drought tolerant rhizobium strains as promising biostimulants for common bean in Northern Spain.

Drought is the most detrimental abiotic stress in agriculture, limiting crop growth and yield and, currently, its risk is increasing due to climate change. Thereby, ensuring food security will be one of the greatest challenges of the agriculture in the nearest future, accordingly it is essential to look for sustainable strategies to cope the negative impact of drought on crops. Inoculation of pulses with biostimulants such as rhizobium strains with high nitrogen fixation efficiency and drought-tolerance, has emerged as a promising and sustainable production strategy. However, some commercial inoculums are not effective under field conditions due to its lower effectiveness against indigenous rhizobium strains in the establishment of the symbiosis. Thus, in the present study, we evaluated the ability to improve drought tolerance in common bean plants of different indigenous rhizobia strains isolated from nearby crop fields in the Basque Country either affected by drought or salinity. The plants in this trial were grown in a climatic chamber under controlled conditions and exposed to values of 30% relative soil water content at the time of harvest, which is considered a severe drought. From the nine bacteria strains evaluated, three were found to be highly efficient under drought (namely 353, A12 and A13). These strains sustained high infectiveness (nodulation capacity) and effectiveness (shoot biomass production) under drought, even surpassing the plants inoculated with the CIAT899 reference strain, as well as the chemically N-fertilized plants. The tolerance mechanisms developed by plants inoculated with 353, A12 and A13 strains were a better adjustment of the cell wall elasticity that prevents mechanical damages in the plasma membrane, a higher WUE and an avoidance of the phenological delay caused by drought, developing a greater number of flowers. These results provide the basis for the development of efficient common bean inoculants able to increase the yield of this crop under drought conditions in the Northern Spain and, thus, to be used as biostimulants. In addition, the use of these efficient nitrogen fixation bacteria strains is a sustainable alternative to chemical fertilization, reducing cost and minimizing its negative impact on environment.

In vitro evaluation of the antagonistic activity of native strains of Trichoderma spp. against Fusarium spp.

Five samples of agricultural soil and five samples of Aloe barbadensis (P. Mill., 1768) plants with symptoms of wilt and root necrosis were collected in five localities of the state of Tamaulipas, México. The aims of this study were the morphological identification, molecular identification and in vitro evaluation of the antagonistic activity of Trichoderma spp. on Fusarium spp. Four strains of Trichoderma asperellum, one strain of Trichoderma harzianum and five strains of Fusarium oxysporum were identified by morphological and molecular methods. The evaluation of the antagonistic activity of T. harzianum isolate (TP) showed the highest inhibition in Fusarium spp. (78.80%). The evaluation of the antagonistic activity of Trichoderma spp. extracts in Fusarium spp. did not show significant differences between treatments (P ≤ 0.05), with Trichoderma growth percentages that oscillated between 81.08 and 94.38%. The native isolate of T. harzianum (TP) showed significant competitive capability against the mycelial growth of F. oxysporum. Trichoderma species are promising agents of biological control in the central area of the State Tamaulipas, Mexico.

A novel strategy to construct multi-strain starter cultures: an insight to evolve from natural to directed fermentation.

Some biotechnological strategies have succeeded in the attempt to imitate natural fermentation, and bioprocesses have been efficiently designed when the product is the result of a unique biological reaction. However, when the process requires more than one biological reaction, few bioprocesses have been successfully designed because the available tools to construct multi-strain starter cultures are not yet well defined. In this work, a novel experimental strategy to construct multi-strain starter cultures with selected native microorganisms from natural fermentation is proposed. The strategy analyses, selects, and defines the number and proportion of each strain that should form a starter culture to be used in directed fermentations. It was applied to evolve natural fermentation to directed fermentation in distilled agave production. The results showed that a starter culture integrated by Kluyveromyces marxianus, Clavispora lusitaniae, and Kluyveromyces marxianus var. drosophilarum in proportions of 35, 32, and 33%, respectively, allows obtaining fermented agave juice containing a 2.1% alcohol yield and a distilled product with a broad profile of aromatic compounds. Hence, the results show, for the first time, a tool that addresses the technical challenge for multi-strain starter culture construction, offering the possibility of preserving the typicity and genuineness of the original traditional product.

Entomopathogenic nematodes and their symbiotic bacteria: from genes to field uses.

The term "microbial control" has been used to describe the use of microbial pathogens (bacteria, viruses, or fungi) or entomopathogenic nematodes (EPNs) to control various insect pest populations. EPNs are among the best biocontrol agents, and major developments in their use have occurred in recent decades, with many surveys having been conducted all over the world to identify EPNs that may have potential in the management of insect pests. For nematodes, the term "entomopathogenic" means "causing disease to insects" and is mainly used in reference to the bacterial symbionts of Steinernema and Heterorhabditis (Xenorhabdus and Photorhabdus, respectively), which cause EPN infectivity. A compendium of our multiannual experiences on EPN surveys and on their collection, identification, characterization, and use in agro-forestry ecosystems is presented here to testify and demonstrate once again that biological control with EPNs is possible and offers many advantages over chemicals, such as end-user safety, minimal damage to natural enemies, and lack of environmental pollution, which are essential conditions for an advanced IPM strategy.

Antifungal potential of biosurfactants produced by strains of Bacillus spp. (Bacillales: Bacillaceae) selected by molecular screening / Potencial antifúngico de biosulfactantes producidos por cepas de Bacillus spp. (Bacillales: Bacillaceae) seleccionadas por tamizaje molecular

Introduction: Bacillus species are used as biological controllers for phytopathogenic fungi, and the mechanisms to produce controllers include biosynthesis of lipopeptide biosurfactants with antifungal activity. Objective: To evaluate the antifungal potential of the biosurfactants produced by Bacillus strains, selected by molecular screening, on Fusarium oxysporum. Methods: We selected four molecular markers, related to the biosynthesis of surfactin, fengicin, and lichenysin (srfA, spf, fenB, LichAA) in nine Bacillus strains. We used two mineral media with several culture conditions, for biosurfactant production, and a well diffusion test for antifungal potential. Results: Only the biosurfactant produced by UFAB25 inhibits the mycelial growth of F. oxysporum (44 % ± 13): this biosurfactant was positive for srfA, spf, and fenB genes involved in the synthesis of surfactin and fengicine. Antifungal activity depends on culture conditions and the strain. Conclusions: Genetic markers are useful to detect strains with antifungal potential, facilitating the selection of bio-controllers. The biosurfactant profile is influenced by the strain and by culture conditions.

Introducción: Especies de Bacillus han sido empleadas como controladores biológicos contra hongos fitopatógenos. Entre los mecanismos utilizados se destaca la biosíntesis de biosurfactantes lipopeptídicos con actividad antifúngica. Objetivo: Evaluar el potencial antifúngico de los biosurfactantes producidos por cepas Bacillus nativas, previamente seleccionadas mediante tamizaje molecular, sobre Fusarium oxysporum. Métodos: Se utilizaron cuatro marcadores moleculares, relacionados con la biosíntesis de surfactina, fengicina y liquenisina (srfA, spf, fenB, LichAA) sobre nueve cepas de Bacillus. Se utilizaron dos medios minerales con diferentes condiciones de cultivo para la producción del biosurfactante. Se evaluó el potencial antifúngico de los biosurfactantes mediante la prueba de difusión en pozos. Resultados: Se determinó que solo el biosurfactante producido por UFAB25 actúa como inhibidor del crecimiento micelial de Fusarium oxysporum (43.6 % ± 13), esta cepa es positiva para los genes srfA, spf y fenB, involucrados en la síntesis de surfactina y fengicina. La actividad antifúngica depende de las condiciones de cultivo y la cepa. Conclusiones: Los marcadores genéticos ayudan a detectar cepas con potencial antifúngico, facilitando la selección de biocontroladores. El perfil del biosurfactante está influenciado no solo por la cepa, sino también por las condiciones del cultivo.

Mycelial compatibility, anastomosis, and nucleus numbers of eight Mexican Hirsutella citriformis strains isolated from Diaphorina citri.

BACKGROUND: Among entomopathogenic fungi, H. citriformis has been recognized as potential biocontrol agent against the Asian citrus psyllid Diaphorina citri (Hemiptera: Liviidae). Nevertheless, this fungus is poorly characterized. Previous molecular studies have shown high sequence similarities among strains, but significant differences in Diaphorina citri virulence. OBJECTIVE: The aim of the present study was to determine mycelial compatibility and anastomosis, and nucleus numbers in mycelium and conidia of eight H. citriformis strains isolated from mycosed D. citri adults collected from several Mexican states. METHODS: Mycelial compatibility and anastomosis evaluation was performed after pairing strains, leading to 36 confrontations, and cultured in chlorate minimum medium to obtain mutants for vegetative compatibility group. RESULTS: Hypha or conidia nuclei were visualized with safranin-O and 3% KOH, and 0.05% trypan blue-lactophenol solution. H. citriformis strains showed compatibly and anastomosis events after confrontation. In addition, they showed one nucleus per conidium and mycelium section. It was not possible to obtain H. citriformis nit mutants from the chlorate concentrations tested. CONCLUSIONS: To date, this is the first report demonstrating mycelial compatibility, anastomosis occurrence, and hyphae and conidia nuclei number among H. citriformis strains.