Manganese homeostasis modulates fungal virulence and stress tolerance in Candida albicans

Due to the scarcity of transition metals within the human host, fungal pathogens have evolved sophisticated mechanisms to uptake and utilize these micronutrients at the infection interface. While considerable attention was turned to iron and copper acquisition mechanisms and their importance in fungal fitness, less was done regarding either the role of manganese (Mn) in infectious processes or the cellular mechanism by which fungal cells achieve their Mn-homeostasis. Here, we undertook transcriptional profiling in the pathogenic fungus Candida albicans experiencing both Mn starvation and excess to capture biological processes that are modulated by this metal. We uncovered that Mn scarcity influences diverse processes associated with fungal fitness including invasion of host cells and antifungal sensitivity. We show that Mn levels influence the abundance of iron and zinc emphasizing the complex crosstalk between metals. The deletion of SMF12, a member of Mn Nramp transporters, confirmed its contribution to Mn uptake. smf12 was unable to form hyphae and damage host cells and exhibited sensitivity to azoles. We found that the unfolded protein response (UPR), likely activated by decreased glycosylation under Mn limitation, was required to recover growth when cells were shifted from an Mn-starved to an Mn-repleted medium. RNA-seq profiling of cells exposed to Mn excess revealed that UPR was also activated. Furthermore, the UPR signaling axis Ire1-Hac1 was required to bypass Mn toxicity. Collectively, this study underscores the importance of Mn homeostasis in fungal virulence and comprehensively provides a portrait of biological functions that are modulated by Mn in a fungal pathogen.

IMPORTANCE

Transition metals such as manganese provide considerable functionality across biological systems as they are used as cofactors for many catalytic enzymes. The availability of manganese is very limited inside the human body. Consequently, pathogenic microbes have evolved sophisticated mechanisms to uptake this micronutrient inside the human host to sustain their growth and cause infections. Here, we undertook a comprehensive approach to understand how manganese availability impacts the biology of the prevalent fungal pathogen, Candida albicans. We uncovered that manganese homeostasis in this pathogen modulates different biological processes that are essential for host infection which underscores the value of targeting fungal manganese homeostasis for potential antifungal therapeutics development.

How to manage transfusion systems in developing countries: The Experience of Eastern and Southern Mediterranean countries

OBJECTIVES

To outline and analyse the national organisation, infrastructure and management of transfusion systems in countries sharing common historical, cultural and economic features and to decipher management trends, in order to potentially benchmark.

BACKGROUND

Little is known regarding transfusion systems in Eastern/southern Mediterranean at a time international organisations are calling for the establishment of a safe and sustainable blood system.

MATERIALS AND METHODS

Data emanating from eight Arabic-speaking Eastern/Southern Mediterranean countries who responded to five surveys were collected and tabulated.

RESULTS

While similarities in terms of supervision by national authorities, authorization of blood centres, quality control and management information system are evident, some significant divergence between these countries do exists. Only Lebanon does not possess a national blood establishment or organisation for blood supply. Blood components are fully government-subsidised in Algeria and Mauritania. Algeria, Morocco and Tunisia have a blood supply that relies mainly on Voluntary non-remunerated donors. Plateletpheresis is performed in all countries except Mauritania while plasmapheresis exists only in Algeria and Egypt. Morocco is the sole country outsourcing its plasma for Plasma derived products.

CONCLUSION

Despite the various challenges facing these countries, lot of progresses have been made so far in the field of transfusion medicine. Yet, nationally coordinated blood programs overviewed by national regulatory authorities and actively supported by local governments are still needed to ensure the optimum level of blood safety.