Integrating contact network structure into tuberculosis epidemiology in meerkats in South Africa: Implications for control

Empirical studies that integrate information on host contact patterns with infectious disease transmission over time are rare. The aims of this study were to determine the relative importance of intra-group social interactions in the transmission of tuberculosis (TB; Mycobacterium bovis infection) in a population of wild meerkats (Suricata suricatta) in South Africa, and to use this information to propose an evidence-based intervention strategy to manage this disease. Detailed behavioural observations of all members of eight meerkat groups (n=134 individuals) were made over 24 months from January 2006 to December 2007. Social network analysis of three types of interaction (aggression, foraging competitions and grooming) revealed social structure to be very stable over time. Clustering of interactions was positively correlated with group size for both aggression (r=0.73) and grooming interactions (r=0.71), suggesting that infections may spread locally within clusters of interacting individuals but be limited from infecting all members of large groups by an apparent threshold in connections between different clusters. Repeated biological sampling every three months of all members of one social group (n=37 meerkats) was undertaken to quantify individual changes in M. bovis infection status. These empirical data were used to construct a dynamic network model of TB transmission within a meerkat group. The results indicated that grooming (both giving and receiving) was more likely than aggression to be correlated with M. bovis transmission and that groomers were at higher risk of infection than groomees. Intervention strategies for managing TB in meerkats that focus on those individuals engaging in the highest amount of grooming are therefore proposed.     

Using multi-scale modelling to predict habitat suitability for species of conservation concern: The grey long-eared bat as a case study

Although spatial scale is important for understanding ecological processes and guiding conservation planning, studies combining a range of scales are rare. Habitat suitability modelling has been used traditionally to study broad-scale patterns of species distribution but can also be applied to address conservation needs at finer scales. We studied the ability of presence-only species distribution modelling to predict patterns of habitat selection at broad and fine spatial scales for one of the rarest mammals in the UK, the grey long-eared bat (Plecotus austriacus). Models were constructed with Maxent using broad-scale distribution data from across the UK (excluding Northern Ireland) and fine-scale radio-tracking data from bats at one colony. Fine-scale model predictions were evaluated with radio-tracking locations from bats from a distant colony, and compared with results of traditional radio-tracking data analysis methods (compositional analysis of habitat selection). Broad-scale models indicated that winter temperature, summer precipitation and land cover were the most important variables limiting the distribution of the grey long-eared bat in the UK. Fine-scale models predicted that proximity to unimproved grasslands and distance to suburban areas determine foraging habitat suitability around maternity colonies, while compositional analysis also identified unimproved grasslands as the most preferred foraging habitat type. This strong association with unimproved lowland grasslands highlights the potential importance of changes in agricultural practices in the past century for wildlife conservation. Hence, multi-scale models offer an important tool for identifying conservation requirements at the fine landscape level that can guide national-level conservation management practices.     

Perception of UV-B by the Arabidopsis UVR8 protein

To optimize their growth and survival, plants perceive and respond to ultraviolet-B (UV-B) radiation. However, neither the molecular identity of the UV-B photoreceptor nor the photoperception mechanism is known. Here we show that dimers of the UVR8 protein perceive UV-B, probably by a tryptophan-based mechanism. Absorption of UV-B induces instant monomerization of the photoreceptor and interaction with COP1, the central regulator of light signaling. Thereby this signaling cascade controlled by UVR8 mediates UV-B photomorphogenic responses securing plant acclimation and thus promotes survival in sunlight.     

Development of a self-replicating plasmid system for Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is a prevalent swine respiratory pathogen that is a major cause of economic loss to pig producers. Control is achieved by a combination of antimicrobials, vaccination and management practices, but current vaccines offer only partial control and there is a need for improved preventative strategies. A major barrier to advances in understanding the pathogenesis of M. hyopneumoniae and in developing new vaccines is the lack of tools to genetically manipulate the organism. We describe the development and optimisation of the first successful plasmid-based system for the genetic manipulation of M. hyopneumoniae. Our artificial plasmids contain the origin of replication (oriC) of M. hyopneumoniae along with tetM, conferring resistance to tetracycline. With these plasmids, we have successfully transformed M. hyopneumoniae strain 232 by electroporation, generating tetracycline resistant organisms. The persistence of extrachromosomal plasmid and maintenance of plasmid DNA over serial passages shows that these artificial plasmids are capable of self-replication in M. hyopneumoniae. In addition to demonstrating the amenability of M. hyopneumoniae to genetic manipulation and in optimising the conditions necessary for successful transformation, we have used this system to determine the minimum functional oriC of M. hyopneumoniae. In doing so, we have developed a plasmid with a small oriC that is stably maintained over multiple passages that may be useful in generating targeted gene disruptions. In conclusion, we have generated a set of plasmids that will be valuable in studies of M. hyopneumoniae pathogenesis and provide a major step forward in the study of this important swine pathogen.     

Fungal and bacterial growth following the application of slurry and anaerobic digestate of livestock manure to temperate pasture soils

How land-application of digestate sourced from anaerobic digestion (AD) of animal waste influences the functioning of a mixed pasture agroecosystem is not well characterised, particularly with regard to the response of the actively growing microbial community. We studied the impact of the liquid AD digestate on the decomposer community in two different soils, seeded with two different common grassland crops; a mixture of either grass or grass/clover in a greenhouse experiment. We studied bacterial (leucine incorporation into bacteria) and fungal (acetate incorporation into ergosterol) growth responses to AD cattle slurry digestate, undigested cattle slurry, mineral fertiliser (NPK and N) added at a rate equivalent to 150?kg?N?ha^?1, and a no-fertiliser control treatment. Differences in fungal and bacterial growth were evident between the soil and sward types. However, the fertilisers consistently stimulated a higher bacterial growth than the no-fertiliser control, and liquid digestate resulted in a level of bacterial growth higher or equal to that of mineral fertiliser, whilst undigested slurry resulted in lower bacterial growth. These fertiliser effects on bacterial growth mirrored the effects on plant growth. In contrast, the fungal community responded only marginally to fertiliser treatments. We conclude that the application of digestate stimulates the bacterial decomposer community in a similar way to that of mineral fertilisers. Our results suggest that mineral fertiliser can be exchanged for liquid digestate with limited impact on the actively growing soil microbial community that, in turn, regulate important soil processes including nutrient cycling in agricultural soils.     

Mapping of quantitative trait loci for seminal root morphology and gravitropic response in rice

In order to gain a better understanding of the complex root traits observed in previous studies using a mapping population derived from a Bala × Azucena cross, an experiment was conducted growing plants in agar-filled Perspex chambers with the aim of identifying quantitative trait loci (QTLs) for both seminal root morphology (SRM) and gravitropic response. A total of four main effect QTLs were detected for SRM (a measurement of the degree of a wavy/curly seminal root phenotype); two were located on chromosome 2, one at the top of chromosome 3 and one on chromosome 11. Two main effect QTLs were detected for the gravitropic response (the degree of bending of the growing seminal root when subjected to a 90° rotation); one on chromosome 6 and 1 on chromosome 11. As well as main effect QTLs, an epistatic interaction was observed for each of the traits. For SRM an interaction was detected between the top and the bottom of chromosome 4. For the gravitropic response an interaction was observed between a location on chromosome 6 and 11. Both these interactions were confirmed by analysis of variance using marker classes and the epistatic gravitropic response was also confirmed using a pair of near isogenic lines. All the SRM QTLs detected in this experiment co-localise with root growth QTLs (root penetration or morphology) detected previously in the mapping population. This information could prove valuable in attempts to identify candidate genes for these potentially valuable QTLs because we could postulate that the underlying genes should be involved in the pathway of gravity detection, signal transduction or the growth response to gravity.