MudPIT Profiling Reveals a Link between Anaerobic Metabolism and the Alkaline Adaptive Response of Listeria monocytogenes EGD-e

Listeria monocytogenes is a foodborne human pathogen capable of causing life-threatening disease in susceptible populations. Previous proteomic analysis we performed demonstrated that different strains of L. monocytogenes initiate a stringent response when subjected to alkaline growth conditions. Here, using multidimensional protein identification technology (MudPIT), we show that in L. monocytogenes EGD-e this response involves an energy shift to anaerobic pathways in response to the extracellular pH environment. Importantly we show that this supports a reduction in relative lag time following an abrupt transition to low oxygen tension culture conditions. This has important implications for the packaging of fresh and ready-to-eat foods under reduced oxygen conditions in environments where potential exists for alkaline adaptation.     

A Prospective Study of Seasonal Variation in Shift‐Work Tolerance

Seasonal effects on shift‐work tolerance were assessed using the Standardized Shiftwork Index and the 21‐item Hamilton Depression Scale. Participants (N=88) mainly worked a two‐day, two‐night, four‐off rotation with 12 h shifts changing at 06∶00 and 18∶00 h in Vancouver, Canada. At this latitude (～49° N), daylength varies seasonally from ～16 to ～8 h, and both daily commutes occur in the dark in mid‐winter and in sunlight in mid‐summer. Questionnaires were completed twice, near the summer and winter solstices (order counterbalanced). Outcome variables were mood, general psychological health, sleep quality, chronic fatigue, physical health, job satisfaction, and social and domestic disruption. Of these, general psychological health and mood were significantly worse in winter, while sleep was more disturbed in summer. In winter, 31% exceeded the cutoff for psychological distress, and >70% scored in the higher than normal range for depressive symptoms. In summer, the proportions dropped to 19% and 53%, respectively. Measures of physical health and psychosocial well‐being showed no seasonal effects. Relationships among explanatory and outcome variables, assessed by linear regression and canonical correlations, were also stable across season. Neuroticism was the strongest predictor of tolerance to shift work. Age was predictive only of sleep disturbance in both summer and winter. These results indicate that time of year can affect important outcome measures in shift‐work assessment and intervention studies. The high average scores on measures of psychological distress and depression in winter suggest that at northern latitudes, some shift schedules may increase the risk of seasonal‐type depression.     

Environmentally Enriched Male Mink Gain More Copulations than Stereotypic,Barren-Reared Competitors

Wild carnivores in zoos, conservation breeding centres, and farms commonly live in relatively small, unstimulating enclosures. Under these captive conditions, in a range of species including giant pandas, black-footed ferrets, and European mink, male reproductive abilities are often poor. Such problems have long been hypothesized to be caused by these animals'' housing conditions. We show for the first time that rearing under welfare-improving (i.e., highly valued and stress-reducing) environmental enrichments enhances male carnivores'' copulatory performance: in mate choice competitions, enriched male American mink (Neovison vison) mated more often than non-enriched males. We screened for several potential mediators of this effect. First was physiological stress and its impact on reproductive physiology; second, stress-mediated changes in morphology and variables related to immunocompetence that could influence male attractiveness; and third, behavioural changes likely to affect social competence, particularly autistic-like excessive routine and repetition (‘perseveration’) as is reflected in the stereotypies common in captive animals. Consistent with physiological stress, excreted steroid metabolites revealed that non-enriched males had higher cortisol levels and lower androgen levels than enriched conspecifics. Their os penises (bacula) also tended to be less developed. Consistent with reduced attractiveness, non-enriched males were lighter, with comparatively small spleens and a trend to greater fluctuating asymmetry. Consistent with impaired social competence, non-enriched males performed more stereotypic behaviour (e.g., pacing) in their home cages. Of all these effects, the only significant predictor of copulation number was stereotypy (a trend suggesting that low bodyweights may also be influential): highly stereotypic males gained the fewest copulations. The neurophysiological changes underlying stereotypy thus handicap males sexually. We hypothesise that such males are abnormally perseverative when interacting with females. Investigating similar problems in other taxa would be worthwhile, since many vertebrates, wild and domestic, live in conditions that cause stereotypic behaviour and/or impair neurological development.     

Assessing the cryptic invasion of a domestic conspecific: American mink in their native range

Control of invasions is facilitated by their early detection, but this may be difficult when invasions are cryptic due to similarity between invaders and native species. Domesticated conspecifics offer an interesting example of cryptic invasions because they have the ability to hybridize with their native counterparts, and can thus facilitate the introgression of maladaptive genes. We assessed the cryptic invasion of escaped domestic American mink (Neovison vison) within their native range. Feral mink are a known alien invader in many parts of the world, but invasion of their native range is not well understood. We genetically profiled 233 captive domestic mink from different farms in Ontario, Canada and 299 free‐ranging mink from Ontario, and used assignments tests to ascertain genetic ancestries of free‐ranging animals. We found that 18% of free‐ranging mink were either escaped domestic animals or hybrids, and a tree regression showed that these domestic genotypes were most likely to occur south of a latitude of 43.13°N, within the distribution of mink farms in Ontario. Thus, domestic mink appear not to have established populations in Ontario in locations without fur farms. We suspect that maladaptation of domestic mink and outbreeding depression of hybrid and introgressed mink have limited their spread. Mink farm density and proximity to mink farms were not important predictors of domestic genotypes but rather, certain mink farms appeared to be important sources of escaped domestic animals. Our results show that not all mink farms are equal with respect to biosecurity, and thus that the spread of domestic genotypes can be mitigated by improved biosecurity.     

Litter N retention over winter for a low and a high phenolic species in the alpine tundra

Mycorrhizal fungus colonization of roots may modify plant metal acquisition and tolerance. In the present study, the contribution of the extraradical mycelium of an arbuscular mycorrhizal (AM) fungus, Glomus mosseae (BEG 107), to the uptake of metal cations (Cu, Zn, Cd and Ni) by cucumber (Cucumis sativus) plants was determined. The influence of the amount of P supplied to the hyphae on the acquisition and partitioning of metal cations in the mycorrhizal plants was also investigated. Pots with three compartments were used to separate root and root-free hyphal growing zones. The shoot concentration of Cd and Ni was decreased in mycorrhizal plants compared to non-mycorrhizal plants. In contrast, shoot Zn and Cu concentrations were increased in mycorrhizal plants. High P supply to hyphae resulted in decreased root Cu concentrations and shoot Cd and Ni concentrations in mycorrhizal plants. These results confirm that some elements required for plant growth (P, Zn, Cu) are taken up by mycorrhizal hyphae and are then transported to the plants. Conversely, Cd and Ni were transported in much smaller amounts by hyphae to the plant, so that arbuscular mycorrhizal fungus colonization could partly protect plants from toxic effects of these elements. Selective uptake and transport of plant essential elements over non-essential elements by AM hyphae, increased growth of mycorrhizal plants, and metal accumulation in the root may all contribute to the successful growth of mycorrhizal plants on metal-rich substrates. These effects are stimulated when hyphae can access sufficient P in soil.     

Population genetic characterisation of dominant Cryptosporidium parvum subtype IIaA15G2R1

The subtype IIaA15G2R1 at the 60 kDa glycoprotein (gp60) gene locus is the most dominant Cryptosporidium parvum infecting dairy cattle and humans in industrialised nations. The reasons for its high transmissibility are not clear, and it remains to be determined whether this subtype represents a homogeneous parasite population. In this study, we sequence-characterised 26 IIaA15G2R subtype specimens and 26 non-IIaA15G2R subtype specimens from the United States, Canada, United Kingdom and Spain at seven other known polymorphic loci, including CP47, CP56, DZ-HRGP, MSC6-5, MSC6-7, RPGR and ZPT. Extensive heterogeneity within IIaA15G2R1 and discordance in typing results between gp60 and other genetic markers were observed. Results of inter-locus and intra-ZPT linkage disequilibrium and recombination analyses indicated that the heterogeneity within IIaA15G2R1 and discordance in typing results among genetic loci were largely due to the occurrence of genetic recombination, mostly within the gp60 subtype IIaA15G2R1. Although there was no clear population diversion between IIaA15G2R and non-IIaA15G2R subtypes, results of STRUCTURE and F_ST analyses suggested the presence of at least two subpopulations; subpopulation 1 had an epidemic population structure and was widely distributed, whereas subpopulation 2 had a clonal population structure and consisted of geographically segregated multilocus subtypes. Genetic recombination between epidemic and geographically segregated C. parvum populations appeared to be a driving force in the emergence of a hyper-transmissible IIaA15G2R1 subtype. Genetic recombination was observed even between the zoonotic IIa subtype family and anthroponotic subtype family IIc at CP56, MSC6-7 and ZPT. Thus, the IIaA15G2R1 subtype at gp60 is likely a fitness marker for C. parvum and the wide spread of IIaA15G2R1 subtype around the world is probably independent of the sequence characteristics at other genetic loci.     

Bioactive compounds from Stuhlmannia moavi from the Madagascar dry forest

Bioassay-directed fractionation of the leaf and root extracts of the antiproliferative Madagascar plant Stuhlmannia moavi afforded 6-acetyl-5,8-dihydroxy-2-methoxy-7-methyl-1,4-naphthoquinone (stuhlmoavin, 1) as the most active compound, with an IC₅₀ value of 8.1 μM against the A2780 human ovarian cancer cell line, as well as the known homoisoflavonoid bonducellin (2) and the stilbenoids 3,4,5′-trihydroxy-3′-methoxy-trans-stilbene (3), piceatannol (4), resveratrol (5), rhapontigenin (6), and isorhapontigenin (7). The structure elucidation of all compounds was based on NMR and mass spectroscopic data, and the structure of 1 was confirmed by a single crystal X-ray analysis. Compounds 2?5 showed weak A2780 activities, with IC₅₀ values of 10.6, 54.0, 41.0, and 74.0 μM, respectively. Compounds 1?3 also showed weak antimalarial activity against Plasmodium falciparum with IC₅₀ values of 23, 26, and 27 μM, respectively.