Burkholderia tropica UNA BACTERIA CON GRAN POTENCIAL PARA SU USO EN LA AGRICULTURA

The Current and Future Role of Microbial Culture Collections in Food Security Worldwide

Food security is the pillar of nutritional wellbeing for food availability, and is necessary to satisfy all physiological needs to thus maintain the general wellbeing of populations. However, global agricultural deficiencies occur due to rapid population growth, causing an increase in competition for resources; such as water, land, and energy, leading to the overexploitation of agro-ecosystems, and the inability to produce a suitable quantity of efficient food. Therefore, the development of sustainable agro-biotechnologies is vital to increase crop yield and quality, reducing the negative impacts caused by intensive non-sustainable agricultural practices. In this way, the genetic and metabolic diversity of soil and plant microbiota in agro-ecosystems are a current and promising alternative to ensure global food security. Microbial communities play an important role in the improvement of soil fertility and plant development by enhancing plant growth and health through several direct and/or indirect mechanisms. Thus, the bio-augmentation of beneficial microbes into agro-ecosystems not only generates an increase in food production but also mitigates the economic, social, and environmental issues of intensive non-sustainable agriculture. In this way, the isolation, characterization, and exploitation of preserved beneficial microbes in microbial culture collections (MCC) is crucial for the ex situ maintenance of native soil microbial ecology focused on driving sustainable food production. This review aims to provide a critical analysis of the current and future role of global MCC on sustainable food security, as providers of a large number of beneficial microbial strains with multiple metabolic and genetic traits.

Effective microorganisms inoculant: Diversity and effect on the germination of palisade grass seeds

Effective microorganisms (EM) are inoculants formed by fungi and bacteria isolated from soil. EM are commonly used by farmers on agronomic crops to stimulate plant growth, but their composition and their benefits has been controverted. This study aimed to analyze the diversity of microorganisms growing in three EM inoculants, as well as to evaluate their efficiency in the germination of palisade grass seeds. The total DNA of the three EM inoculants was extracted, the 16S rRNA and ITS genes were amplified by PCR and sequenced on the Illumina MiSeq platform. Germination tests were conducted with three type of the EM, in three concentration and two times of the immersion. The bacterial group was the most abundant in EM, followed by fungi. Bacterial operational taxonomic units OTUs were shared by all EMs. Pre-treatments of palisade grass seeds with EMs resulted in a higher germination percentage (% G) and germination speed index (IVG) when EM was used at concentration of 1 or 2% in water. Seed immersion for 5 min was more efficient than immersion for 24 h. We can conclude that EM of different origin can share microbial groups and diversity of microorganisms, besides being an alternative to increase palisade grass seeds germination.

The importance of antimicrobial compounds produced by beneficial bacteria on the biocontrol of phytopathogens

Bacteria produce antimicrobial compounds to compete for nutrients and space in a particular habitat. Antagonistic interactions can be evaluated by several methodologies including the double-layer agar and simultaneous inhibition assays. Among the well-known inhibitory substances produced by bacteria are the broad-spectrum antibiotics, organic acids, siderophores, antifungal, and bacteriocins. The most studied bacterial genera able to produce these inhibitory substances are Enterococcus, Lactococcus, Streptomyces, Bacillus, Pseudomonas, Klebsiella, Escherichia, and Burkholderia. Some beneficial bacteria can promote plant growth and degrade toxic compounds in the environment representing an attractive solution to diverse issues in agriculture and soil pollution, particularly in fields with damaged soils where pesticides and fertilizers have been indiscriminately used. Beneficial bacteria may increase plant health by inhibiting pathogenic microorganisms; some examples include Gluconacetobacter diazotrophicus, Azospirullum brasilense, Pseudomonas fluorescens, Pseudomonas protegens, and Burkholderia tropica. However, most studies showing the antagonistic potential of these bacteria have been performed in vitro, and just a few of them have been evaluated in association with plants. Several inhibitory substances involved in pathogen antagonism have not been elucidated yet; in fact, we know only 1 % of the bacterial diversity in a natural environment leading us to assume that many other inhibitory substances remain unexplored. In this review, we will describe the characteristics of some antimicrobial compounds produced by beneficial bacteria, the principal methodologies performed to evaluate their production, modes of action, and their importance for biotechnological purposes.

Assessment of bacterial inoculant formulated with Paraburkholderia tropica to enhance wheat productivity

Paraburkholderia tropica is an endophytic nitrogen-fixing bacterium isolated from the rhizosphere, rhizoplane, and internal tissues of sugarcane and corn plants in different geographical regions. Other plant-growth-promoting abilities, such as phosphate solubilization and antifungal activity, have also been reported for this bacterium. With an aim at investigating the potential use of P. tropica as an inoculant for improving the performance of wheat crop, in this work we evaluated an experimental inoculant formulated with P. tropica MTo-293 with respect to root colonization, the practical aspects of its application, and the effects under field conditions when applied to wheat seeds. Bacterial colonization was monitored by culture dependent techniques and the wheat yield determined by quantifying the total grain production in two different seasons. Rhizoplane and endophytic colonization in wheat roots was achieved efficiently (on average, 8 and 4 log colony-forming units/g fresh weight, respectively) even at relatively low concentrations of viable bacteria in the inoculum under controlled conditions. P. tropica was compatible with a widely used fungicide, maintained viability for 48 h once applied to seeds, and was also able to colonize wheat roots efficiently. Furthermore, we were able to formulate an inoculant that maintained bacterial viability for relatively long time periods. Preliminary field assays were realized, and even though the average yields values for the inoculated treatments remained above the uninoculated ones, no significant effects of inoculation were detected with or without fertilization. The correct physiologic behavior of P. tropica suggests the necessity to continue with field experiments under different conditions.

Identificación de bacterias solubilizadoras de fosfatos en un Andisol de la región cafetera colombiana

El fósforo es un elemento esencial para el cultivo de café, sin embargo la mayoría de los suelos en Colombia presentan niveles bajos de este nutriente. La presencia de microorganismos solubilizadores de fosfatos (MSF) es una de las estrategias para suplir su demanda, en ese sentido se aislaron 26 bacterias rizosféricas de Typic melanudans de Cajibío (Cauca, Colombia), en tres agroecosistemas: café sin sombra, café con sombra y relicto de bosque secundario, evaluándoles la eficiencia solubilizadora de P (ESF) en Ca-P, Al-P, Fe-P en medios Pikovskaya sólido y líquido, obteniendo la secuencia de solubilización Ca-P > Al-P > Fe-P. Los dos aislamientos bacterianos con mayor ESF se identificaron por extracción del ADN y análisis del gen 16S rRNA como Kocuria sp, y Bacillus subtilis. Posteriormente se cuantificaron e identificaron los ácidos orgánicos presentes en las tres fuentes de fosforo por HPLC, siendo ellos los ácidos cítrico, glucónico, D- y L-málico, D- y L-láctico con mayor presencia en Ca-P- Kocuria sp. En todas las condiciones, se observó que ocurrió acidificación de los medios, siendo más fuerte en Fe-P y Al-P.