5 research outputs found
Modulation of Shigella virulence in response to available oxygen in vivo
Bacteria coordinate expression of virulence determinants in response to localized microenvironments in their hosts. Here we show that Shigella flexneri, which causes dysentery, encounters varying oxygen concentrations in the gastrointestinal tract, which govern activity of its type three secretion system (T3SS). The T3SS is essential for cell invasion and virulence. In anaerobic environments (for example, the gastrointestinal tract lumen), Shigella is primed for invasion and expresses extended T3SS needles while reducing Ipa (invasion plasmid antigen) effector secretion. This is mediated by FNR (fumarate and nitrate reduction), a regulator of anaerobic metabolism that represses transcription of spa32 and spa33, virulence genes that regulate secretion through the T3SS. We demonstrate there is a zone of relative oxygenation adjacent to the gastrointestinal tract mucosa, caused by diffusion from the capillary network at the tips of villi. This would reverse the anaerobic block of Ipa secretion, allowing T3SS activation at its precise site of action, enhancing invasion and virulence
An Overview and Recent Advances in Vector and Scalar Formalisms: Space/Time Discretizations in Computational Dynamics—A Unified Approach
Beneficial soil microbiome for sustainable agricultural production
The projected increase in world population and the need to reduce the
reliance on non-renewable inputs, such as synthetic agrochemicals, are challenging
the current vision of agriculture. In particular, to achieve a fair and sustainable
global food security, disruptive changes in crop production are unavoidable.
A promising strategy proposes to exploit the metabolic capabilities of soil microbial
communities, i.e., the microbiome, to conjugate stable yield with reduced impact on
the agroecosystem. In this chapter, we introduce the microbiome populating the root-soil interface from an evolutionary perspective. Next, we discuss the molecular
bases of plant-microbe interactions in soil and how these interactions impact plant
growth, development and health. We illustrate how plant-probiotic members of the
microbiome can be isolated from soil and further characterized for their biological
activities, a key pre-requisite for translational applications. In addition, we focus on
paradigmatic examples of soil microbes turned into inoculants for agriculture, their
fate on soil, their impact on the native microbiome and the beneficial effects exerted
on crop productio