DNA fingerprinting of Australian isolates of Mycobacterium avium subsp paratuberculosis using IS900 RFLP

OBJECTIVES: To evaluate additional restriction enzymes for IS900 RFLP of Mycobacterium avium subsp paratuberculosis and examine the genetic diversity among Australian isolates for epidemiological studies of Johne's disease. DESIGN AND PROCEDURE: Seventy-one isolates of M paratuberculosis from cattle, sheep, goat, alpaca and rhinoceros in six Australian States and the Northern Territory, reference strains and reference DNA from previously characterised strains were tested for genetic variation. Bst EII, Pvu II and Pst I restriction enzymes were used, and four others (Bam HI, Alu I, Xho I and Dra I) were assessed for their ability to detect polymorphisms. Multiple isolates from some animals were tested. RESULTS: Bam HI, was the most effective enzyme for identifying polymorphisms (12 types), followed by Bst EII (11 types). Both Pvu II and Pst I were relatively ineffectual. Fifteen different types were identified, 12 in clinical isolates. Most isolates were cattle (C) strains and fell into the C1 (n = 28) and C3 (n = 32) groupings. All isolates from alpaca were type C1, and bovine isolates were commonly C1 (n = 15) or C3 (n = 28). All of the sheep were infected with sheep (S) strains; no S strains were identified in cattle. Two of six isolates from one animal had single band differences. CONCLUSION: The epidemiological features of M paratuberculosis in Australia are similar to those reported in New Zealand, where cattle and sheep are commonly infected with different strains. However, because of the lack of polymorphism identified within the major groups, it is unlikely that DNA fingerprinting will have a significant role in epidemiological studies of Johne's disease, unless an unusual strain in being studied.     

Context matters: the landscape matrix determines the population genetic structure of temperate forest herbs across Europe

Landscape Ecology - Plant populations in agricultural landscapes are mostly fragmented and their functional connectivity often depends on seed and pollen dispersal by animals. However, little is...     

The effects of poplar (P. trichocarpa × deltoides) on soil biological properties in a silvoarable system

A silvoarable experimental site in Buckinghamshire, England combined rows of poplar trees with an arable rotation. Soil properties were investigated using soil carbon and the bodysize of invertebrates. Four years after establishment, the soil within and 1 m from the tree rows has significantly higher soil organic matter and invertebrate populations. These effects do not extend far beyond the crown diameter.     

Advantages of a new agar medium in the primary isolation of Mycobacterium bovis

Suspect tuberculous lesions from 116 cattle were examined histologically and cultured for Mycobacterium bovis using 5 different media. The media used were: B83, an agar medium incorporating bovine blood and sodium pyruvate; Middlebrook's agar; 2 variations of Stonebrink's medium; L?wenstein-Jensen medium. The B83 medium and a modification of Stonebrink's medium which had a lowered concentration of malachite green were most successful, detecting 95.2% of tuberculous animals when used together. The B83 medium detected isolates approximately 1 week earlier and had more colonies than the Stonebrink's modification. A combination of 2 slopes of B83 and 2 slopes of modified Stonebrink's medium is recommended for routine culture of samples.     

Preparation, assessment and preservation of antigen from Brucella abortus strain 45/20 for use in the rough antigen complement fixation test

Two methods of extraction were used to prepare antigens from Brucella abortus rough strain 45/20. The antigens were assessed for use in the complement fixation test. A suitable antigen was prepared using the saline extraction method of Miller et al. (1976) and used extensively in CF tests. Four methods of preservation were compared; -20 degrees C, -196 degrees C, 0.5% phenol at 4 degrees C, and lyophilisation. The antigen could be stored at -20 degrees C or -196 degrees C for up to 2 years.     

Long term effects of enhanced nitrogen deposition on a lowland dry heath in southern Britain

Experimental additions of ammonium sulphate to a nitrogen-poor dry heathland have been carried out since 1989. There are four nitrogen treatments: a control (receiving artificial rain only), a low treatment which receives an additional 7.7 kg N ha^?1 yr^?1, a high treatment receiving 15.4 kg N ha^?1 yr^?1 and an alternating treatment which receives either the control or the high nitrogen additions, in alternate years. The estimated background deposition at the study site is 13–18 kg N ha^?1 yr^?1, a value similar to the critical load that has been suggested for the conversion of lowland heath to grassland. Over the past 5 years there have been significant stimulations in shoot growth, flowering, canopy density and litter production. Flowering, in particular, strongly reflects nitrogen additions in the alternating treatment. Current models of the response of dry Calluna heathlaud to enhanced nitrogen deposition suggest that higher tissue nitrogen levels will occur and will be accompanied by heightened sensitivity to secondary stresses. This may in turn lead to canopy breakdown and replacement by grassland. The application of nitrogen at deposition rates only slightly in excess of the critical load over five years has produced small, non-significant increases in shoot nitrogen content. However, there is clear evidence of a large positive effect on shoot growth, flowering, litter production and canopy density of Calluna. The observation of these responses at the application rates used in this study supports the current proposals for critical loads of nitrogen for lowland heaths.     

The influence of field shape, area and surrounding landscape on plant species richness in grazed ex-fields

Over the past 100 years species-rich semi-natural grasslands have decreased dramatically in Western Europe, where former arable fields (ex-fields) are used instead as pasture. The disappearance of semi-natural grasslands has caused a threat to the biodiversity in agricultural landscapes. Many typical grassland plants are dispersal limited, thus grazed ex-fields can be used to investigate if species spontaneously colonise these new grassland habitats. We examined the relationship between surrounding landscape, field area, shape, distance between edge and centre, and plant species diversity in ex-fields that had been grazed for 15-18 years. The results showed that there were 35% more plant species in fields surrounded by commercial forestry production compared to those surrounded by open agricultural landscape. Area and shape did not influence species richness, although there was increasing number of species in the centre with decreasing distance from the edge. Twenty-five percent of the species where typical grassland species, and ex-fields surrounded by forest had 91% more grassland species compared to those in the open landscape. It is possible to increase grassland plant occurrences by grazing ex-fields surrounded by forest or other grassland remnant habitats, particularly in landscapes where grazed semi-natural grasslands are scarce.