Quantification of carbon and phosphorus co-limitation in bacterioplankton: new insights on an old topic

Because the nature of the main resource that limits bacterioplankton (e.g. organic carbon [C] or phosphorus [P]) has biogeochemical implications concerning organic C accumulation in freshwater ecosystems, empirical knowledge is needed concerning how bacteria respond to these two resources, available alone or together. We performed field experiments of resource manipulation (2×2 factorial design, with the addition of C, P, or both combined) in two Mediterranean freshwater ecosystems with contrasting trophic states (oligotrophy vs. eutrophy) and trophic natures (autotrophy vs. heterotrophy, measured as gross primary production:respiration ratio). Overall, the two resources synergistically co-limited bacterioplankton, i.e. the magnitude of the response of bacterial production and abundance to the two resources combined was higher than the additive response in both ecosystems. However, bacteria also responded positively to single P and C additions in the eutrophic ecosystem, but not to single C in the oligotrophic one, consistent with the value of the ratio between bacterial C demand and algal C supply. Accordingly, the trophic nature rather than the trophic state of the ecosystems proves to be a key feature determining the expected types of resource co-limitation of bacteria, as summarized in a proposed theoretical framework. The actual types of co-limitation shifted over time and partially deviated (a lesser degree of synergism) from the theoretical expectations, particularly in the eutrophic ecosystem. These deviations may be explained by extrinsic ecological forces to physiological limitations of bacteria, such as predation, whose role in our experiments is supported by the relationship between the dynamics of bacteria and bacterivores tested by SEMs (structural equation models). Our study, in line with the increasingly recognized role of freshwater ecosystems in the global C cycle, suggests that further attention should be focussed on the biotic interactions that modulate resource co-limitation of bacteria.This research was supported by Junta de Andalucía (Excelencia P09-RNM-5376 to JMMS) and the Spanish Ministry Ciencia e Innovación (CGL2011-23681 to PC)

PROFESSIONAL PRACTICE OF DENTIST IN FRONT OF THE NATIONAL POLICY OF MORBIDITY REDUCTION BY ACCIDENTS AND VIOLENCE

The authors conducted a systematic review of scientific production about the National Policy on Reduction of Morbidity and Mortality from Accidents and Violence and its implications for the professional dentist. The objective was to determine how this issue has been addressed, identifying the existing literature on the role of a trader before this Policy. The search was conducted in the Virtual Health Library (VHL), selecting 16 articles, 9 found in databases Lilacs and SciELO and 7 only available in Lilacs. Of all selected studies, analyzed all references pointed out the importance of the qualification of health professionals to cope with external causes. However, only 3 references cited dentists throughout the article, without mentioning any implication for the performance of this professional front Policy. Thus, it is believed that the National Policy on Reduction of Morbidity and Mortality from Accidents and Violence has struggled for its implementation, requiring, therefore, disclosure and strength to legitimize itself.2941064107