A Critical Look at the Combined Use of Sulfur and Oxygen Isotopes to Study Microbial Metabolisms in Methane-Rich Environments

The benthic foraminiferal δ34S records flux and timing of paleo methane emissions

In modern environments, pore water geochemistry and modelling simulations allow the study of methane (CH₄) sources and sinks at any geographic location. However, reconstructing CH₄ dynamics in geological records is challenging. Here, we show that the benthic foraminiferal δ³⁴S can be used to reconstruct the flux (i.e., diffusive vs. advective) and timing of CH₄ emissions in fossil records. We measured the δ³⁴S of Cassidulina neoteretis specimens from selected samples collected at Vestnesa Ridge, a methane cold seep site in the Arctic Ocean. Our results show lower benthic foraminiferal δ³⁴S values (∼20‰) in the sample characterized by seawater conditions, whereas higher values (∼25–27‰) were measured in deeper samples as a consequence of the presence of past sulphate-methane transition zones. The correlation between δ³⁴S and the bulk benthic foraminiferal δ¹³C supports this interpretation, whereas the foraminiferal δ¹⁸O-δ³⁴S correlation indicates CH₄ advection at the studied site during the Early Holocene and the Younger-Dryas – post-Bølling. This study highlights the potential of the benthic foraminiferal δ³⁴S as a novel tool to reconstruct the flux of CH₄ emissions in geological records and to indirectly date fossil seeps.

Diagnosis of invasive fungal disease in children: a narrative review

Introduction: Invasive fungal diseases (IFD) represent important causes of morbidity and mortality in pediatrics. Early diagnosis and treatment of IFD is associated with better outcome and this entails the need to use fast and highly sensitive and specific methods that can support clinicians in the management of IFD.Areas covered: A narrative review was performed on conventional diagnostic methods such as culture, microscopy and histopathology are still gold standard but are burdened by a lack of sensitivity and specificity; on the other hand, imaging and noninvasive antigen-based such as beta-D-glucan, galactomannan and molecular biomarkers are the most convenient nonculture methods for diagnosis and monitoring effects of therapy. Aim of the present review is to summarize what is available in these fields at end of the second decade of the third millennium and look for future perspectives.Expert opinion: Promising and useful diagnostic methods have been applied in infectious disease diagnosis in clinical practice or in designing platforms. Unfortunately, most of them are not standardized or validated in pediatric population. However, clinicians should be aware of all innovative diagnostic tools to use in combination with conventional diagnostic methods for a better management of pathology and patient.