Actividades de la APCM en 2022 y visibilidad de sus conferencias; un quehacer que tiene que ser reforzado

La divulgación del conocimiento es imperante para el crecimiento de una sociedad y es uno de los compromisos que tiene la Asociación Poblana de Ciencias Microbiológicas. En este artículo editorial se hace un análisis del número de lecturas, visualización de conferencias y descargas de los archivos PDF de las charlas 2022. Se observa que, aunque hay un consumo adecuado del material publicado, es importante hacer más trabajo de difusión de las publicaciones con el fin de tener un mayor impacto en nuestra población de habla hispana. Además, en este trabajo se muestran otras actividades que ha tenido la APCM a lo largo del año 2022

Diversidad bacteriana metilotrófica asociada a la cactácea neobuxbaumia macrocephala, endémica en riesgo de la reserva Tehuacán Cuicatlán

"Los microorganismos metilotróficos desempeñan un papel importante en múltiples ecosistemas así como en áreas de interés humano debido a su diversidad, sus vías metabólicas únicas en la naturaleza, así como su capacidad para asimilar y oxidar sustratos de bajo costo. Las bacterias metilotróficas utilizan como fuente de energía y de carbono compuestos reducidos en carbono que no tienen enlaces C-C. Estos microorganismos tienen una distribución amplia que incluye suelos, ambientes acuáticos y plantas. Este trabajo se planteó con el propósito de obtener conocimiento de la diversidad microbiana metilotrófica cultivable del ambiente de la cactácea neobuxbaumia macrocephala.

Novel bio-fertilizer based on nitrogen-fixing bacterium immobilized in a hydrotalcite/alginate composite material

"The bacterium Streptomyces sp. is a common genus of the actinomycetes class found in soils and rhizospheres. This bacterium can produce substances with bio-stimulant capacity through the fixation of nitrogen from the air. In this work, the Streptomyces sp. bacterium was immobilized on a ZnMgAl-hydrotalcite clay and embedded in calcium alginate beads to generate a novel bio-composite that functions as a bacterial reservoir and as a controlled release material for bacteria to be used as a bio-fertilizer. The results showed that the novel bacterium-hydrotalcite/alginate bio-composite was very efficient as a bio-fertilizer showing a plant length of 64 mm in only 14 days of growing, which corresponds to an increase of ca. 760% in the lettuce plant growth in comparison with the materials without bacteria. In short, the present results demonstrate that the hydrotalcite and alginate served as an excellent container to keep the bacteria alive, providing nutrients to them and controlling their delivery"

¿Es funcional la biorremediación en la eliminación de níquel en un suelo contaminado?

La contaminación por metales pesados representa un problema creciente en la cultura industrializada. Representan una amenaza biológica, pues no son biodegradables, aunque existen mecanismos que poseen los organismos para acumular, traslocar, transformar, inmovilizar o estabilizarlos. El níquel es un metal pesado presente en descargas mineras, en la industria de la fundición, refinación de elementos metálicos, entre otras. Es conocido que la asociación de plantas con algunas bacterias benéficas ayuda a las plantas a tolerar niveles de estrés como la contaminación por metales pesados. En el presente trabajo se propuso remediar suelo contaminado con níquel, con ayuda de Medicago sativa, una planta hiperacumuladora, en asociación con la cepa promotora de crecimiento y biorremediadora Pseudomonas putida KT2440. Se establecieron tratamientos semi-hidropónicos donde se trasplantaron germinados de M. sativa inoculados y no con la cepa bacteriana. Se determinó la concentración del metal en el suelo a distintos tiempos de tratamiento por medio de espectrofotometría de absorción atómica. La cepa bacteriana, 15 días posteriores al montaje del experimento, no fue posible detectarla, tampoco se observó tolerancia al estrés por la planta. Sin embargo, hubo un establecimiento prolífico de hongos y los ensayos de absorción atómica revelan una disminución significativa en los niveles de concentración de níquel en el suelo

Growth inhibition of pathogenic microorganisms by Pseudomonas protegens EMM-1 and partial characterization of inhibitory substances.

The bacterial strain, EMM-1, was isolated from the rhizosphere of red maize ("Rojo Criollo") and identified as Pseudomonas protegens EMM-1 based on phylogenetic analysis of 16S rDNA, rpoB, rpoD, and gyrB gene sequences. We uncovered genes involved in the production of antimicrobial compounds like 2,4-diacetylphloroglucinol (2,4-DAPG), pyoluteorin, and lectin-like bacteriocins. These antimicrobial compounds are also produced by other fluorescent pseudomonads alike P. protegens. Double-layer agar assay showed that P. protegens EMM-1 inhibited the growth of several multidrug-resistant (MDR) bacteria, especially clinical isolates of the genera Klebsiella and β-hemolytic Streptococcus. This strain also displayed inhibitory effects against diverse fungi, such as Aspergillus, Botrytis, and Fusarium. Besides, a crude extract of inhibitory substances secreted into agar was obtained after the cold-leaching process, and physicochemical characterization was performed. The partially purified inhibitory substances produced by P. protegens EMM-1 inhibited the growth of Streptococcus sp. and Microbacterium sp., but no inhibitory effect was noted for other bacterial or fungal strains. The molecular weight determined after ultrafiltration was between 3 and 10 kDa. The inhibitory activity was thermally stable up to 60°C (but completely lost at 100°C), and the inhibitory activity remained active in a wide pH range (from 3 to 9). After treatment with a protease from Bacillus licheniformis, the inhibitory activity was decreased by 90%, suggesting the presence of proteic natural compounds. All these findings suggested that P. protegens EMM-1 is a potential source of antimicrobials to be used against pathogens for humans and plants

The Viable but Non-Culturable (VBNC) State, a Poorly Explored Aspect of Beneficial Bacteria

Many bacteria have the ability to survive in challenging environments; however, they cannot all grow on standard culture media, a phenomenon known as the viable but non-culturable (VBNC) state. Bacteria commonly enter the VBNC state under nutrient-poor environments or under stressful conditions. This review explores the concept of the VBNC state, providing insights into the beneficial bacteria known to employ this strategy. The investigation covers different chemical and physical factors that can induce the latency state, cell features, and gene expression observed in cells in the VBNC state. The review also covers the significance and applications of beneficial bacteria, methods of evaluating bacterial viability, the ability of bacteria to persist in environments associated with higher organisms, and the factors that facilitate the return to the culturable state. Knowledge about beneficial bacteria capable of entering the VBNC state remains limited; however, beneficial bacteria in this state could face adverse environmental conditions and return to a culturable state when the conditions become suitable and continue to exert their beneficial effects. Likewise, this unique feature positions them as potential candidates for healthcare applications, such as the use of probiotic bacteria to enhance human health, applications in industrial microbiology for the production of prebiotics and functional foods, and in the beer and wine industry. Moreover, their use in formulations to increase crop yields and for bacterial bioremediation offers an alternative pathway to harness their beneficial attributes

Compatible bacterial mixture, tolerant to desiccation, improves maize plant growth

<div><p>Plant growth-promoting rhizobacteria (PGPR) increase plant growth and crop productivity. The inoculation of plants with a bacterial mixture (consortium) apparently provides greater benefits to plant growth than inoculation with a single bacterial strain. In the present work, a bacterial consortium was formulated containing four compatible and desiccation-tolerant strains with potential as PGPR. The formulation had one moderately (<i>Pseudomonas putida</i> KT2440) and three highly desiccation-tolerant (<i>Sphingomonas</i> sp. OF178, <i>Azospirillum brasilense</i> Sp7 and <i>Acinetobacter</i> sp. EMM02) strains. The four bacterial strains were able to adhere to seeds and colonize the rhizosphere of plants when applied in both mono-inoculation and multi-inoculation treatments, showing that they can also coexist without antagonistic effects in association with plants. The effects of the bacterial consortium on the growth of blue maize were evaluated. Seeds inoculated with either individual bacterial strains or the bacterial consortium were subjected to two experimental conditions before sowing: normal hydration or desiccation. In general, inoculation with the bacterial consortium increased the shoot and root dry weight, plant height and plant diameter compared to the non-inoculated control or mono-inoculation treatments. The bacterial consortium formulated in this work had greater benefits for blue maize plants even when the inoculated seeds underwent desiccation stress before germination, making this formulation attractive for future field applications.</p></div

Bacterial survival ratio (BSR) of bacterial strains after desiccation stress.

<p>Bacterial survival ratio (BSR) of bacterial strains after desiccation stress.</p

Effect of bacterial inoculation on the growth of maize 45 days after sowing (DAS) under greenhouse conditions.

<p>A) Shoot dry weight, B) Root dry weight, C) Plant height, D) Plant diameter. WDS indicates experiment with seeds not subjected to desiccation stress before germination (Exp. 1). DS indicates experiment with seeds subjected to desiccation stress before germination (Exp. 2), E) Plants from germinated seeds inoculated with the bacterial consortium (WDS), F) Plants from germinated seeds inoculated with the bacterial consortium (DS). Bar color key: sky blue, non-inoculated control; orange, <i>A</i>. <i>brasilense</i> Sp7; gray, <i>P</i>. <i>putida</i> KT2440; yellow, <i>Acinetobacter</i> sp. EMM02; dark blue, <i>Sphingomonas</i> sp. OF178; green/bacterial consortium. Each value represents the media of the data for 35 independent plants with the respective standard deviation. Identical letters in each bar group indicate that the values were not significantly different at P ≤ 0.05 based on Student’s <i>t</i> or Tukey’s test.</p

Bacterial survival ratio (BSR) of bacteria associated with blue maize seeds subjected to 18 days of desiccation.

<p>Fig 3A, BSR determination for seeds inoculated with single bacterial strains. Fig 3B, BSR determination for seeds inoculated with the bacterial consortium. Purple squares represent <i>Sphingomonas</i> sp. OF178, green triangles represent <i>Acinetobacter</i> sp. EMM02, red rectangles represent <i>A</i>. <i>brasilense</i> Sp7, and blue diamonds represent <i>P</i>. <i>putida</i> KT2440.</p