Worldwide, bacterial resistance is one of the most severe public health problems. Currently, the failure of antibiotics to counteract superbugs highlights the need to search for new molecules with antimicrobial potential to combat them. The objective of this research was to evaluate the antimicrobial activity of Bacillus amyloliquefaciens BS4 against Gram-negative bacteria. Thirty yeasts and thirty-two Bacillus isolates were tested following the agar well-diffusion method. Four Bacillus sp. strains (BS3, BS4, BS17, and BS21) showed antagonistic activity against E. coli ATCC 25922 using bacterial culture (BC) and the cell-free supernatant (CFS), where the BS4 strain stood out, showing inhibitory values of 20.50 ± 0.70 mm and 19.67 ± 0.58 mm for BC and CFS, respectively. The Bacillus sp. BS4 strain can produce antioxidant, non-hemolytic, and antimicrobial metabolites that exhibit activity against several microorganisms such as Salmonella enterica, Klebsiella pneumoniae, Shigella flexneri, Enterobacter aerogenes, Proteus vulgaris, Yersinia enterocolitica, Serratia marcescens, Aeromonas sp., Pseudomonas aeruginosa, Candida albicans, and Candida tropicalis. According to the characterization of the supernatant, the metabolites could be proteinaceous. The production of these metabolites is influenced by carbon and nitrogen sources. The most suitable medium to produce antimicrobial metabolites was TSB broth. The one-factor-at-a-time method was used to standardize parameters such as pH, agitation, temperature, carbon source, nitrogen source, and salts, resulting in the best conditions of pH 7, 150 rpm, 28 °C, starch (2.5 g/L), tryptone (20 g/L), and magnesium sulfate (0.2 g/L), respectively. Moreover, the co-culture was an excellent strategy to improve antimicrobial activity, achieving maximum antimicrobial activity with an inhibition zone of 21.85 ± 1.03 mm. These findings position the Bacillus amyloliquefaciens BS4 strain as a promising candidate for producing bioactive molecules with potential applications in human health.

Mine tailings are produced by mining activities and contain diverse heavy metal ions, which cause environmental problems and have negative impacts on ecosystems. Different microorganisms, including yeasts, play important roles in the absorption and/or adsorption of these heavy metal ions. This work aimed to analyze proteins synthesized by the yeast Yarrowia lipolytica AMJ6 (Yl-AMJ6), isolated from Andean mine tailings in Peru and subjected to stress conditions with common heavy metal ions. Yeast strains were isolated from high Andean water samples impacted by mine tailings from Yanamate (Pasco, Peru). Among all the isolated yeasts, the Yl-AMJ6 strain presented LC50 values of 1.06 mM, 1.42 mM, and 0.49 mM for the Cr⁺⁶, Cu⁺², and Cd⁺² ions, respectively. Proteomic analysis of theYl-AMJ6 strain under heavy metal stress showed that several proteins were up- or downregulated. Biological and functional analysis of these proteins showed that they were involved in the metabolism of proteins, nucleic acids, and carbohydrates; response to oxidative stress and protein folding; ATP synthesis and ion transport; membrane and cell wall; and cell division. The most prominent proteins that presented the greatest changes were related to the oxidative stress response and carbohydrate metabolism, suggesting the existence of a defense mechanism in these yeasts to resist the impact of environmental contamination by heavy metal ions.

Evaluación de la diversidad de algas fitoplanctónicas como indicadores de la calidad del agua en lagunas altoandinas del departamento de Pasco (Perú)

En el siglo XVIII, durante el virreinato del Perú, la mina Cerro de Pasco inició la explotación de plata y plomo, actividad que persiste hasta la actualidad y que continúa contaminando con metales pesados el suelo y las aguas de la cuenca del río San Juan, en el departamento de Pasco. Con el fin de analizar la eficacia de las algas verdes altoandinas Mougeotia sp. y Spirogyra sp. en la bioremoción de cobre y plomo, se recolectaron muestras de ambas especies en el río San Juan, y tras cultivarlas en medio de cultivo Chu 10. El estudio se realizó con un diseño experimental factorial de 3 x 3 x 2 (3 indican los tres tratamientos de cobre y de plomo, y 2 son las dos especies de algas verdes filamentosas), con 5 repeticiones por tratamiento. Los resultados mostraron tanto Mougeotia sp. y Spirogyra sp. con el tratamiento de 30 mg L-1 de plomo lograron las eficiencias de remoción más elevadas, del 97 % y 87,6 % de bioremoción de plomo, respectivamente. Ambas especies registraron una notable capacidad de bioremoción de plomo y cobre, empero con disminución significativa en su biomasa y en el contenido de clorofila a.

Acidithiobacillus ferrivorans es un acidófilo psicrotolerante capaz de hacer crecer y oxidar sustratos ferrosos y sulfurosos a bajas temperaturas. Hasta la fecha se han caracterizado seis genomas de este organismo; sin embargo, la evidencia de un plásmido en esta especie ha sido informado solo una vez, por lo que no hay un rol concluyente de los plásmidos en la especie. Aquí, dos plásmidos novedosos de A. ferrivorans PQ33 se caracterizaron molecularmente y se compararon a escala genómica. Se secuenciaron y anotaron los genomas de dos plásmidos (12 kpb y 10 kpb) de A. ferrivorans PQ33 (NZ_LVZL01000000). Los plásmidos, denominados pAfPQ33-1 (NZ_CP021414.1) y pAfPQ33-2 (NZ_CP021415.1), presentaron 9 CDS y 13 CDS, respectivamente. El análisis in silico mostró proteínas involucradas en la conjugación (TraD, MobA, Eep y XerD), sistemas de toxina-antitoxina (HicA y HicB), replicación (RepA y proteína de unión al ADN), regulación de la transcripción (CopG), chaperona DnaJ y un gen de virulencia (vapD). Además, los plásmidos contienen secuencias similares a las porinas selectivas de fosfato O y P y una proteína diguanilato ciclasa-fosfodiesterasa. La presencia de estos genes sugiere la posibilidad de transferencia horizontal, un sistema regulador de mantenimiento de plásmidos y adhesión a sustratos para especies de A. ferrivorans y PQ33. Este es el primer informe de plásmidos en esta cepa.