The SPI-2 type III secretion system restricts motility of Salmonella-containing vacuoles

Intracellular replication of Salmonella enterica occurs in membrane-bound compartments, called Salmonella-containing vacuoles (SCVs). Following invasion of epithelial cells, most SCVs migrate to a perinuclear region and replicate in close association with the Golgi network. The association of SCVs with the Golgi is dependent on the Salmonella-pathogenicity island-2 (SPI-2) type III secretion system (T3SS) effectors SseG, SseF and SifA. However, little is known about the dynamics of SCV movement. Here, we show that in epithelial cells, 2 h were required for migration of the majority of SCVs to within 5 μm from the microtubule organizing centre (MTOC), which is located in the same subcellular region as the Golgi network. This initial SCV migration was saltatory, bidirectional and microtubule-dependent. An intact Golgi, SseG and SPI-2 T3SS were dispensable for SCV migration to the MTOC, but were essential for maintenance of SCVs in that region. Live-cell imaging between 4 and 8 h post invasion revealed that the majority of wild-type SCVs displaced less than 2 μm in 20 min from their initial starting positions. In contrast, between 6 and 8 h post invasion the majority of vacuoles containing sseG, sseF or ssaV mutant bacteria displaced more than 2 μm in 20 min from their initial starting positions, with some undergoing large and dramatic movements. Further analysis of the movement of SCVs revealed that large displacements were a result of increased SCV speed rather than a change in their directionality, and that SseG influences SCV motility by restricting vacuole speed within the MTOC/Golgi region. SseG might function by tethering SCVs to Golgi-associated molecules, or by controlling microtubule motors, for example by inhibiting kinesin recruitment or promoting dynein recruitment

Evidence of Long-Distance Coastal Sea Migration of Atlantic Salmon, Salmo Salar, Smolts from Northwest England (River Derwent).

Publication history: Accepted - 10 January 2022; Published online - 26 January 2022Background Combining data from multiple acoustic telemetry studies has revealed that west coast England Atlantic salmon (Salmo salar L.) smolts used a northward migration pathway through the Irish Sea to reach their feeding grounds. Hundred Atlantic salmon smolts were captured and tagged in May 2020 in the River Derwent, northwest England as part of an Environment Agency/Natural England funded project. Results Three tagged smolts were detected on marine acoustic receivers distributed across two separate arrays from different projects in the Irish Sea. One fish had migrated approximately 262 km in 10 days from the river mouth at Workington Harbour, Cumbria to the northernmost receiver array operated by the SeaMonitor project; this is the longest tracked marine migration of an Atlantic salmon smolt migrating from the United Kingdom. This migrating fish displayed behaviours which resulted in fast northward migration. The remaining two fish were detected on a receiver array operated by a third project: the Collaborative Oceanography and Monitoring for Protected Areas and Species (COMPASS). Conclusion These detections further provide evidence that migration to reach marine feeding grounds of at least a proportion of salmon smolts from rivers draining into the Irish Sea is northerly, though without a southern marine array it is impossible to conclude that this is the only route. The pattern of these detections would not have been possible without the collaborative efforts of three distinct and separately funded projects to share data. Further work is required to fully understand migration trajectories in this species on the west coast of the British Isles.The main Funding bodies for this project were the Environment Agency, Cumbria and Natural England, Cumbria. Additional funding was provided by The Derwent Owners Association and Bowland Game: Isel Fishings

Quantifying fossil fuel methane emissions using observations of atmospheric ethane and an uncertain emission ratio

We present a method for estimating fossil fuel methane emissions using observations of methane and ethane, accounting for uncertainty in their emission ratio. The ethane:methane emission ratio is incorporated as a spatially and temporally variable parameter in a Bayesian model, with its own prior distribution and uncertainty. We find that using an emission ratio distribution mitigates bias from using a fixed, potentially incorrect emission ratio and that uncertainty in this ratio is propagated into posterior estimates of emissions. A synthetic data test is used to show the impact of assuming an incorrect ethane:methane emission ratio and demonstrate how our variable parameter model can better quantify overall uncertainty. We also use this method to estimate UK methane emissions from high-frequency observations of methane and ethane from the UK Deriving Emissions linked to Climate Change (DECC) network. Using the joint methane–ethane inverse model, we estimate annual mean UK methane emissions of approximately 0.27 (95 % uncertainty interval 0.26–0.29) Tg yr−1 from fossil fuel sources and 2.06 (1.99–2.15) Tg yr−1 from non-fossil fuel sources, during the period 2015–2019. Uncertainties in UK fossil fuel emissions estimates are reduced on average by 15 % and up to 35 % when incorporating ethane into the inverse model, in comparison to results from the methane-only inversion

Inshore and offshore marine migration pathways of Atlantic salmon post-smolts from multiple rivers in Scotland, England, Northern Ireland and Ireland

The migratory behavior of Atlantic salmon (Salmo salar) post-smolts in coastal waters is poorly understood. In this collaborative study, 1914 smolts, from 25 rivers, in four countries were tagged with acoustic transmitters during a single seasonal migration. In total, 1105 post-smolts entered the marine study areas and 438 (39.6%) were detected on a network of 414 marine acoustic receivers and an autonomous underwater vehicle. Migration pathways (defined as the shortest distance between two detections) of up to 575 km and over 100 days at sea were described for all 25 populations. Post-smolts from different rivers, as well as individuals from the same river, used different pathways in coastal waters. Although difficult to generalize to all rivers, at least during the year of this study, no tagged post-smolts from rivers draining into the Irish Sea were detected entering the areas of sea between the Hebrides and mainland Scotland, which is associated with a high density of finfish aquaculture. An important outcome of this study is that a high proportion of post-smolts crossed through multiple legislative jurisdictions and boundaries during their migration. This study provides the basis for spatially explicit assessment of the impact risk of coastal pressures on salmon during their first migration to sea

Inshore and offshore marine migration pathways of Atlantic salmon post-smolts from multiple rivers in Scotland, England, Northern Ireland, and Ireland

The migratory behavior of Atlantic salmon (Salmo salar) post-smolts in coastal waters is poorly understood. In this collaborative study, 1914 smolts, from 25 rivers, in four countries were tagged with acoustic transmitters during a single seasonal migration. In total, 1105 post-smolts entered the marine study areas and 438 (39.6%) were detected on a network of 414 marine acoustic receivers and an autonomous underwater vehicle. Migration pathways (defined as the shortest distance between two detections) of up to 575 km and over 100 days at sea were described for all 25 populations. Post-smolts from different rivers, as well as individuals from the same river, used different pathways in coastal waters. Although difficult to generalize to all rivers, at least during the year of this study, no tagged post-smolts from rivers draining into the Irish Sea were detected entering the areas of sea between the Hebrides and mainland Scotland, which is associated with a high density of finfish aquaculture. An important outcome of this study is that a high proportion of post-smolts crossed through multiple legislative jurisdictions and boundaries during their migration. This study provides the basis for spatially explicit assessment of the impact risk of coastal pressures on salmon during their first migration to sea

Requirement of the SPI-2 T3SS and effector SseG for SCV association with the MTOC

<p><b>Copyright information:</b></p><p>Taken from "The SPI-2 type III secretion system restricts motility of -containing vacuoles"</p><p></p><p>Cellular Microbiology 2007;9(10):2517-2529.</p><p>Published online 07 Jun 2007</p><p>PMCID:PMC2062534.</p><p>© 2007 The Authors; Journal compilation © 2007 Blackwell Publishing Ltd</p> A. Representative images of HeLa cells infected for 2 h and 8 h with mutant Typhimurium. Infected cells were fixed in ice-cold methanol and triple labelled for (green in merged images), giantin (blue in merged images) and γ-tubulin (red in merged images). Cells were analysed by confocal microscopy and images represent combined projections of multiple z-sections. Scale bars, 5 μm. B. Percentage of mutant, mutant and wt Typhimurium bacteria within 5 μm from the MTOC over an 8 h time-course. Error bars not apparent if less than 0.1; -values are indicated above bars, compared with corresponding wt values

Time-lapse video microscopy analysis of the movement of SCVs towards the Golgi in HeLa cells

<p><b>Copyright information:</b></p><p>Taken from "The SPI-2 type III secretion system restricts motility of -containing vacuoles"</p><p></p><p>Cellular Microbiology 2007;9(10):2517-2529.</p><p>Published online 07 Jun 2007</p><p>PMCID:PMC2062534.</p><p>© 2007 The Authors; Journal compilation © 2007 Blackwell Publishing Ltd</p> To allow visualization of the Golgi, HeLa cells were transiently transfected with a vector encoding MannII-EGFP. Transfected cells were infected with wt Typhimurium expressing the red fluorescent protein (DsRed). A. Graphical representation of the distance between red fluorescence centroid () and green fluorescence centroid (Golgi) in every frame of six time-lapse sequences; images were taken at 1 min intervals. Each colour represents a single SCV. B. In the upper left panel an SCV trajectory (corresponding to the blue curve in ), is superimposed on the fluorescent and DIC image of the infected HeLa cell. The boxed region is magnified in subsequent panels, which show merged fluorescent images at 30 min intervals (see ). Scale bar, 5 μm. C. Change of speed over time is shown for two distinct SCVs. Data are from time-lapse sequences where images were acquired at 5 s intervals. One SCV (blue line), had an average speed of 0.045 ± 0.004 μm; the other (red line) had an average speed of 0.017 ± 0.001 μm s

Analysis of wt, and vacuole directionality and speed between 6 h and 8 h p

<p><b>Copyright information:</b></p><p>Taken from "The SPI-2 type III secretion system restricts motility of -containing vacuoles"</p><p></p><p>Cellular Microbiology 2007;9(10):2517-2529.</p><p>Published online 07 Jun 2007</p><p>PMCID:PMC2062534.</p><p>© 2007 The Authors; Journal compilation © 2007 Blackwell Publishing Ltd</p>i. SCVs were imaged every 5 s for 5 min. A. Trajectories of small and large displacing vacuoles containing wt, and mutant bacteria. Trajectories were reoriented to start at = 0 with the first displacement vector pointing in the same direction (+x, +y) in a standardized grid. The number of SCVs examined and the average cosine are indicated for each category. B. Mean speeds of small and large displacing vacuoles containing wt, and bacteria. C. Scatter plot in which the speeds of individual 5 s movements of vacuoles containing wt, and bacteria undergoing large displacements were plotted against the distance of the vacuole from the Golgi centroid at the end of its 5 s movement. Spearman correlation -value and -values are indicated