Background
Salmonella pathogenicity island (SPI)-13 is conserved in many serovars of S. enterica, including S. Enteritidis, S. Typhimurium and S. Gallinarum. However, it is absent in typhoid serovars such as S. Typhi and Paratyphi A, which carry SPI-8 at the same genomic location. Because the interaction with macrophages is a critical step in Salmonella pathogenicity, in this study we investigated the role played by SPI-13 and SPI-8 in the interaction of S. Enteritidis and S. Typhi with cultured murine (RAW264.7) and human (THP-1) macrophages.Results
Our results showed that SPI-13 was required for internalization of S. Enteritidis in murine but not human macrophages. On the other hand, SPI-8 was not required for the interaction of S. Typhi with human or murine macrophages. Of note, the presence of an intact copy of SPI-13 in a S. Typhi mutant carrying a deletion of SPI-8 did not improve its ability to be internalized by, or survive in human or murine macrophages.ConclusionsAltogether, our results point out to different roles for SPI-13 and SPI-8 during Salmonella infection. While SPI-13 contributes to the interaction of S. Enteritidis with murine macrophages, SPI-8 is not required in the interaction of S. Typhi with murine or human macrophages. We hypothesized that typhoid serovars have lost SPI-13 and maintained SPI-8 to improve their fitness during another phase of human infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s40659-017-0109-8) contains supplementary material, which is available to authorized users.
Dislocations are at the heart of the plastic behavior of crystalline
materials yet it is notoriously difficult to perform quantitative,
non-intrusive, measurements of their single or collective properties.
Dislocation density is a critical variable that determines dislocation
mobility, strength and ductility. On the one hand, individual dislocations can
be probed in detail with transmission electron microscopy. On the other hand,
their collective properties must be simulated numerically. Here we show that
ultrasound technology can be used to measure dislocation density. This
development rests on theory---a generalization of the Granato-L\"ucke theory
for the interaction of elastic waves with dislocations---and Resonant
Ultrasound Spectroscopy (RUS) measurements. The chosen material is aluminum, to
which different dislocation contents were induced through annealing and cold
rolling processes. The dislocation densities obtained with RUS compare
favorably with those inferred from X-ray diffraction, using the modified
Williamson-Hall method
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