RESUMO
Biological nitrogen fixation is limited to several groups of prokaryotes, some of them reduce nitrogen as free-living nitrogen-fixing bacteria. Protozoa predation on these latter releases sequestered nitrogen that may enhance the formation of new bacterial biomass and possibly increase nitrogen fixation within soil microbial communities. We aim to evaluate the predation effect of Colpoda sp. on two nitrogen fixers: Azospirillum lipoferum and Stenotrophomonas sp. during their lag, early exponential, and exponential phases. The kinetics of bacterial population growth was determined in the predators' presence or absence and the effect of predation on the rate of N fixation was evaluated through the reduction of acetylene to ethylene technique. Colpoda sp. showed a non-significant difference in preferences between the two species offered as prey. Consequently, the abundance of A. lipoferum and Stenotrophomonas sp. decreased significantly due to predator's pressure and both species responded by increasing their specific growth rate. Likewise, predation promoted greater nitrogen fixation rate by CFU during the lag phase in A. lipoferum (0.20 nM/CFU with predation vs 0.09 nM/CFU without predation) and Stenotrophomonas sp. (0.22 nM/CFU vs 0.09 nM/CFU respectively). During early exponential phase (29 h), the rate diminished to 0.13 and 0.05 nM/CFU in A. lipoferum and to 0.09 nM/CFU and 0.05 nM/CFU in Stenotrophomonas sp. Finally, during the exponential phase (52 h), only A. lipoferum without predation produced 0.003 nM/CFU of ethylene. Thus, the nitrogenase activity was higher in the lag and the early exponential phases when predator activity was involved.
Assuntos
Cilióforos , Fixação de Nitrogênio , Animais , Bactérias , Nitrogênio , Comportamento PredatórioRESUMO
La rápida propagación del SARS-CoV-2 ha ocasionado grandes desafíos, algunos de ellos relacionados con la gestión y la visibilidad de la información. Los profesionales de las instituciones de información enfrentaron el reto de tener que reorganizar sus servicios en un breve tiempo, con un componente tecnológico esencial para lograr la virtualidad ante el imperativo indiscutible del distanciamiento físico. Como parte del Plan de enfrentamiento desplegado por Cuba durante esta crisis sanitaria, el Centro Nacional de Información de Ciencias Médicas (CNICM/Infomed) desempeña un rol fundamental, al actuar como proveedor y facilitador de las fuentes, herramientas y servicios de información científica especializada, además de garantizar la plataforma tecnológica para todo el sistema nacional de salud y la población. El presente documento se propone describir el flujo de trabajo concebido por esta institución, los espacios y modos empleados para la producción y difusión de la información científica durante la epidemia, así como los aportes realizados (elaboración de productos y desarrollo e implementación de herramientas y servicios( para apoyar las investigaciones científicas y la toma de decisiones en salud durante la pandemia de la COVID-19(AU)
The fast spread of SARS-CoV-2 has posed big challenges, some of which are related to information management and visibility. Professionals from information institutions have been faced with having to reorganize their services in a short time, with an essential technological component to achieve virtuality in face of the unavoidable imperative of physical distancing. The National Medical Sciences Information Center (CNICM/Infomed) plays a fundamental role in the response plan implemented by Cuba during this health crisis, serving as facilitator and provider of specialized scientific information services, sources and tools, and supplying the required technological platform for the entire national health system and the population. The present document is aimed at describing the workflow devised by this institution, the spaces and modes used for the production and dissemination of scientific information during the epidemic, and the contributions made to the creation of products and the development and implementation of tools and services to support health scientific research and decision making during the COVID-19 pandemic(AU)