Diversity and enzymatic potentialities of Bacillus sp. strains isolated from a polluted freshwater ecosystem in Cuba.

Genotypic and phenotypic characterization of Bacillus spp. from polluted freshwater has been poorly addressed. The objective of this research was to determine the diversity and enzymatic potentialities of Bacillus spp. strains isolated from the Almendares River. Bacilli strains from a polluted river were characterized by considering the production of extracellular enzymes using API ZYM. 14 strains were selected and identified using 16S rRNA, gyrB and aroE genes. Genotypic diversity of the Bacillus spp. strains was evaluated using pulsed field gel electrophoresis. Furthermore, the presence of genetic determinants of potential virulence toxins of the Bacillus cereus group and proteinaceous crystal inclusions of Bacillus thuringiensis was determined. 10 strains were identified as B. thuringiensis, two as Bacillus megaterium, one as Bacillus pumilus and one as Bacillus subtilis. Most strains produced proteases, amylases, phosphatases, esterases, aminopeptidases and glucanases, which reflect the abundance of biopolymeric matter in Almendares River. Comparison of the typing results revealed a spatio-temporal distribution among B. thuringiensis strains along the river. The results of the present study highlight the genotypic and phenotypic diversity of Bacillus spp. strains from a polluted river, which contributes to the knowledge of genetic diversity of Bacilli from tropical polluted freshwater ecosystems.

Caracterización fisiológica de la comunidad microbiana endófita de la caña de azúcar / Physiological characterization of sugarcane’s endophytic microbial community

El uso desmedido de fertilizantes químicos nitrogenados y pesticidas ha traído graves consecuencias ambientales, por lo que se ha prestado gran atención al estudio de la microbiota nativa de los cultivos y sus beneficios a la planta, incluyendo la caña de azúcar. Este trabajo se realizó con el objetivo de caracterizar la microbiota nativa de la caña de azúcar. Se utilizaron 5 cepas bacterianas y 50 aislados provenientes del interior de este cultivo. Se determinó la actividad nitrogenasa y la influencia de la fuente de carbono, nitrógeno y el pH en la misma, mediante cromatografía gaseosa. Se detectó la producción de ácido indolacético por Dot-Immunobinding y el método de Salkowski. Del total de cepas y aislados, 19 mostraron actividad nitrogenasa, con valores entre 100 y 5000 //g/mL, y 6, Gluconacetobacter diazotrophicus PAl-5, Gluconacetobacter diazotrophicus 1-05, Gluconacetobacter diazotrophicus 4-02, aislado 17, aislado 30 y aislado 305; además, tienen la capacidad de producir AIA (valores entre 1,7 y 2,5 JMg/mL). Se demostró que las fuentes nutricionales y el pH del medio de cultivo influyen sobre la actividad nitrogenasa de las cepas representativas de la comunidad endófita.

Excessive application of chemical nitrogen fertilisers and pesticides has badly affected the environment. This has led to great interest being shown in studying a crop’s native microbial community and its benefit for plants. This paper was thus aimed at characterising sugarcane’s endophytic microbial community. 5 sugar cane strains and 50 isolates were used. Gas chromatography was used for measuring nitrogenase activity and the influence of carbon and nitrogen sources and pH on cultures. Indol acetic (IAA) production was detected by Dot-Immunobinding and Salkowski’s method. These results show that 19 strains and isolates had nitrogenase activity, values ranging from 100 to 5000 /zg/mL; 6 of them produced IAA (values ranging from 1,7 to 2,5 //g/mL): Gluconacetobacter iazotrophicus PAl-5, Gluconacetobacter diazotrophicus 1-05, Gluconacetobacter diazotrophicus 4-02, 17, 30 and 305. It was demonstrated that culture medium nutrient sources and pH affectedthe nitrogenase activity of the strains representing the endophytic community.