Modelling the introduction and spread of non‐native species: international trade and climate change drive ragweed invasion

Biological invasions are a major driver of global change, for which models can attribute causes, assess impacts and guide management. However, invasion models typically focus on spread from known introduction points or non‐native distributions and ignore the transport processes by which species arrive. Here, we developed a simulation model to understand and describe plant invasion at a continental scale, integrating repeated transport through trade pathways, unintentional release events and the population dynamics and local anthropogenic dispersal that drive subsequent spread. We used the model to simulate the invasion of Europe by common ragweed (Ambrosia artemisiifolia), a globally invasive plant that causes serious harm as an aeroallergen and crop weed. Simulations starting in 1950 accurately reproduced ragweed's current distribution, including the presence of records in climatically unsuitable areas as a result of repeated introduction. Furthermore, the model outputs were strongly correlated with spatial and temporal patterns of ragweed pollen concentrations, which are fully independent of the calibration data. The model suggests that recent trends for warmer summers and increased volumes of international trade have accelerated the ragweed invasion. For the latter, long distance dispersal because of trade within the invaded continent is highlighted as a key invasion process, in addition to import from the native range. Biosecurity simulations, whereby transport through trade pathways is halted, showed that effective control is only achieved by early action targeting all relevant pathways. We conclude that invasion models would benefit from integrating introduction processes (transport and release) with spread dynamics, to better represent propagule pressure from native sources as well as mechanisms for long‐distance dispersal within invaded continents. Ultimately, such integration may facilitate better prediction of spatial and temporal variation in invasion risk and provide useful guidance for management strategies to reduce the impacts of invasion.     

Incidence of lysogenic, colicinogenic and siderophore-producing strains among human non-pathogenicEscherichia coli

The current incidence ofEscherichia coli strains in healthy humans capable of producing the inhibitory exoproducts, such as temperate bacteriophages, corpuscular or HMW (high-molar mass) and proteinaceous or LMW (low-molar mass) colicins and siderophores was determined. Fifty-threeE. coli strains were collected from the colons of 53 healthy human volunteers in Brno (Czechia) and tested for spontaneous and induced production of inhibitory exoproducts in a cross-test against each other. Of the strains tested, 37.7% produced bacteriophages, 41.5% produced from one to several LMW colicins, 11.3% formed HMW colicins and 15.1% (eight strains) produced exocellular siderophores different from enterochelin. Of these, seven strains formed aerobactin and one strain formed an untyped siderophore.E. coli strains differ greatly in the incidence of colicinogeny and lysogeny from its closest systemic relatives in the genusEscherichia and therefore should not be regarded as a model bacterium in this respect. This work was supported by grants from theGrant Agency of the Czech Republic (310/01/0013 and 310/03/1091) and by the institutional support of theMinistry of Education, Youth and Sports of the Czech Republic (MŠM 002 162 2415).     

The γ134.5 Protein of Herpes Simplex Virus 1 Is Required To Interfere with Dendritic Cell Maturation during Productive Infection

The γ₁34.5 protein of herpes simplex virus 1 is an essential factor for viral virulence. In infected cells, this viral protein prevents the translation arrest mediated by double-stranded RNA-dependent protein kinase R. Additionally, it associates with and inhibits TANK-binding kinase 1, an essential component of Toll-like receptor-dependent and -independent pathways that activate interferon regulatory factor 3 and cytokine expression. Here, we show that γ₁34.5 is required to block the maturation of conventional dendritic cells (DCs) that initiate adaptive immune responses. Unlike wild-type virus, the γ₁34.5 null mutant stimulates the expression of CD86, major histocompatibility complex class II (MHC-II), and cytokines such as alpha/beta interferon in immature DCs. Viral replication in DCs inversely correlates with interferon production. These phenotypes are also mirrored in a mouse ocular infection model. Further, DCs infected with the γ₁34.5 null mutant effectively activate naïve T cells whereas DCs infected with wild-type virus fail to do so. Type I interferon-neutralizing antibodies partially reverse virus-induced upregulation of CD86 and MHC-II, suggesting that γ₁34.5 acts through interferon-dependent and -independent mechanisms. These data indicate that γ₁34.5 is involved in the impairment of innate immunity by inhibiting both type I interferon production and DC maturation, leading to defective T-cell activation.Herpes simplex virus 1 (HSV-1) is a human pathogen responsible for localized mucocutaneous lesions and encephalitis (51). Following primary infection, HSV-1 establishes a latent or lytic infection in which the virus interacts with host cells, which include dendritic cells (DCs), required to initiate adaptive immune responses (36). Immature DCs, which reside in almost all peripheral tissues, are able to capture and process viral antigens (15). In this process, DCs migrate to lymph nodes, where they mature and present antigens to T cells. Mature DCs display high levels of major histocompatibility complex class II (MHC-II) and costimulatory molecules such as CD40, CD80, and CD86. Additionally, DCs release proinflammatory cytokines such as interleukin-12 (IL-12), tumor necrosis factor alpha, alpha interferon (IFN-α), and IFN-β, which promote DC maturation and activation. An important feature of functional DCs is to activate naïve T cells, and myeloid submucosal and lymph node resident DCs are responsible for HSV-specific T-cell activation (2, 45, 52). Moreover, DCs play a direct role in innate antiviral immunity by secreting type I IFN.HSV-1 is capable of infecting both immature and mature DCs (20, 24, 34, 38, 42). A previous study suggested that HSV entry into DCs requires viral receptors HVEM and nectin-2 (42). Upon HSV infection, plasmacytoid DCs detect viral genome through Toll-like receptor 9 (TLR9) and produce high levels of IFN-α (16, 23, 30, 40). In contrast, myeloid DCs, which are major antigen-presenting cells, recognize viral components through distinct pathways, independently of TLR9 (16, 36, 40). It has been suggested previously that HSV proteins or RNA intermediates produced during viral replication trigger myeloid DCs (16, 40). Indeed, a protein complex that consists of HSV glycoproteins B, D, H, and L stimulates the expression of CD40, CD83, CD86, and cytokines in myeloid DCs (41). Hence, DCs sense HSV through TLR-dependent and -independent mechanisms (16, 40, 41). Nevertheless, HSV replication compromises DC functions and subsequent T-cell activation (3, 20, 24, 42). HSV-1 interaction with immature DCs results in the downregulation of costimulatory molecules and cytokines (20, 34, 38, 42). While HSV-2 induces rapid apoptosis, HSV-1 does so with a delayed kinetics in human DCs (4, 20, 38). HSV-1 is also reported to interfere with functions of mature DCs (24, 39). Upon infection, HSV-1 induces the degradation of CD83 but not CD80 or CD86 in mature DCs (24, 25). Additionally, HSV-1 reduces levels of the chemokine receptors CCR7 and CXCR4 on mature DCs and subsequently impairs DC migration to the respective chemokine ligands CCL19 and CXCL12 (39).Although HSV infection impairs DC functions, viral components responsible for this impairment have not been thoroughly investigated. It has been suggested previously that the virion host shut-off protein (vhs) of HSV-1 contributes partially to the viral block of DC activation (43). This activity is thought to stem from the ability of vhs to destabilize host mRNA. Emerging evidence suggests that ICP0 perturbs the function of mature DCs, where it mediates CD83 degradation via cellular proteasomes (25). Findings from related studies show that ICP0 inhibits the induction of IFN-stimulated genes mediated by IFN regulatory factor 3 (IRF3) or IRF7 in other cell types (11, 27, 32, 33). However, the link of ICP0 activities to DC maturation remains to be established. Recently, we found that γ₁34.5, an HSV virulence factor, associates with and inhibits TANK-binding kinase 1 (TBK1), an essential component of TLR-dependent and -independent pathways that activates IRF3 and cytokine expression (49). Interestingly, an HSV mutant lacking γ₁34.5 stimulates MHC-II surface expression in glioblastoma cells (47). These observations raise the hypothesis that γ₁34.5 may modulate DC maturation during HSV infection.In this study, we report that γ₁34.5 is required to perturb DC maturation during HSV infection, leading to impaired T-cell activation. Wild-type virus, but not the γ₁34.5 null mutant, suppresses the expression of costimulatory molecules as well as cytokines in DCs. We provide evidence that the viral block of DC maturation is associated with reduced IFN-α/β secretion. Furthermore, the expression of γ₁34.5 inhibits DC-mediated allogeneic T-cell activation and IFN-γ production. IFN-neutralizing antibodies partially reverse DC maturation induced by the γ₁34.5 null mutant. These results shed light on the role of γ₁34.5 relevant to DC maturation and T-cell responses in HSV infection.     

Hepatic and branchial glutathione S-transferases of two fish species: Substrate specificity and biotransformation of microcystin-LR

Liver and gills of roach (Rutilus rutilus) and silver carp (Hypophthalmichthys molitrix) were examined for glutathione S-transferases (GSTs) contents and their substrate specificity and capacity to biotransform microcystin-LR (MC-LR). GSTs and other glutathione (GSH) affine proteins were purified using a GSH-agarose matrix and separated by anionic chromatography (AEC). Substrate specificities were determined photometrical for 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), 4-nitrobenzyl chloride (pNBC) and ethacrynic acid (ETHA). Biotransformation rate of MC-LR was determined by high performance liquid chromatography (HPLC). Roach exhibited different hepatic and branchial GST activities for used substrates (DNB, pNBC and DCNB) compared to silver carp but not for ethacrynic acid. It suggests that, both fish species have similar amount of pi and/or alpha class, which were the dominant GST classes in liver and gills. Gills of both fish species contained a higher number of GST isoenzymes, but with lower activities and ability of MC-LR biotransformation than livers. GST isoenzymes from roach had higher activity to biotransform MC-LR (conversion rate ranging up to 268 ng MC-LR min^? 1 mL^? 1 hepatic enzyme) than that isolated from silver carp. Without any prior contact to MC-LR or another GST inducer, roach seems to be better equipped for microcystin biotransformation than silver carp.     

Taurine Levels in Discrete Brain Nuclei of Rats

Concentrations of taurine have been measured in 44 microdissected rat brain nuclei or areas. Taurine is ubiquitously present and distributed unevenly in the rat brain: the ratio of the highest (pyriform cortex) to lowest (midbrain reticular formation) concentrations is 4.7:1. High taurine levels were found in cerebral cortical areas, caudate-putamen, cerebellum, median eminence, and supraoptic nucleus. Acute pain stress reduced taurine levels in the hypothalamus and the lower brainstem nuclei but not in cortical areas. Increased locomotor and behavioral activities following a high dose of amphetamine elevated taurine concentrations significantly in the substantia nigra and locus ceruleus.     

Phospholipid characteristics and neutral lipid fatty acid composition related to temperature and nutritional conditions in ecologically important amphipod species from the northern Baltic Sea

Lipid composition of the benthic, stenothermal amphipod Monoporeia affinis collected from constantly cold deep-water (> 80 m) regions of the northern Baltic Sea was analysed in detail to study phospholipid characteristics, its relation to thermal adaptation as well as potential effects of food quality and seasonal variability. Similar measurements were performed on the littoral, eurythermic amphipod Gammarus spp. Fatty acid (FA) composition of storage lipids of Pontoporeia femorata, a sibling species of M. affinis, was also studied. Interannual and interspecies variability in selected FA was observed both in triacylglycerols (TAG) and phospholipids (PL). Differences in monounsaturated vs. polyunsaturated (MUFA/PUFA) FA combinations of phosphatidyl ethanolamine (PE) diacyl and alkylacyl subgroups were also observed. Seasonal variability in M. affinis was considerably lesser compared to Gammarus spp. A literature synopsis shows that in diacyl PE the share of the FA combination MUFA/PUFA increases with lowering body temperature (40-55% in cold-adapted organisms vs. 5-15% in warm adapted ones), signifying that this characteristic is probably in key position concerning regulation of membrane fluidity in temperature adaptation. According to this feature M. affinis belongs to the group of cold-adapted stenothermic species (Group 1) while eurythermic Gammarus spp. settles in the Group 2 (cold-acclimatized) or 3 (warm-acclimatized/tropical) depending on the status of temperature adaptation. Omnivory and/or periodical food item switching is an important strategy in benthic organisms in high-latitude areas characterised by recurring long poor-nutritional periods. Since many benthic species utilise a time-averaged, integrated food source from phytal and animal matter from various sources the FA composition of TAG of the amphipod species measured here do not exclusively point towards any specific feeding mode or food source. In general, using selected FA as food source markers to assess the diet of field collected more-or-less omnivoric species cannot be considered as an optimal approach. The current study gives more insight to the biochemistry of biological membranes of aquatic crustaceans that is essential in estimation of the capacity of the thermal adaptation/acclimatization of organisms as well as the potential effects of food quality on storage lipids.     

Differences in transpiration of Norway spruce drought stressed trees and trees well supplied with water

The paper focuses on the evaluation of transpiration as a physiological process, which is very sensitive to drought stress. Reactions of 25-year-old Norway spruce (Picea abies (L.) Karst.) trees to drought were examined during 2009 summer. Sap flow rate (SF), meteorological and soil characteristics were measured continually. Vapour pressure deficit of the air (VPD) and cumulative transpiration deficit (KTD) was calculated. During the second half of the vegetation period, the decrease in soil water content was observed and irrigation was applied to a group of spruce trees, while the second group was treated under natural soil drought. On the days, when the differences in transpiration between irrigated (IR) and non-irrigated (NIR) trees were significant (21 days), transpiration of NIR trees was only 23% of the transpiration of IR trees. We found significant differences in transpiration when the soil water content (SWC) of NIR variant at a depth of 5–15 cm ranged from 10.4 to 13.7%. Under both regimes of water availability, daily transpiration significantly responded to atmospheric conditions. However, the influence of all assessed meteorological parameters on SF of NIR trees was significantly lower than on IR tree. The dependency of transpiration on evaporative demands of atmosphere decreased with the decreasing soil moisture. Cumulative transpiration deficit of the stand during the entire evaluated period was 50.9 mm. The difference between the transpiration of the mean NIR tree and of the mean IR tree was 278.8 L over the assessed period of 47 days (5.9 L per day). The transpiration of NIR trees was 40.3% from the transpiration of IR trees during this period.