Methanotrophs from natural ecosystems for ruminant methane mitigation

Enteric fermentation of methane by ruminant animals represents a major source of anthropogenic methane production. Methane produced in this manner is released to the atmosphere where it is highly efficient at absorbing thermal radiation, which consequently increases the global surface temperature. Although many different strategies to control ruminant methane emissions have been considered, few are currently considered viable. Obligate and acultative methane oxidising bacteria (MOB) and anaerobic methane oxidising archaea (ANME) play a fundamental role in the carbon cycle by metabolising methane before it is released into the atmosphere. Because of this, methanotrophic microorganisms represent a novel biological control agent in mitigating ruminant methane emissions. This project aims to characterise methanotrophic microorganisms from a range of environments, and to subsequently determine the metabolic activity of these microorganisms under in vitro rumen-like conditions.

Archaeaphage therapy to control rumen methanogens

Phage therapy is becoming increasingly important as a means of eradicating or controlling microbial populations and has been raised as a potential strategy to reduce methane emissions from ruminants. To date, very little is currently known about phages which may infect the methane-producing archaeal strains (methanogens) dominant within the rumen of Australian cattle, such as the Methanobrevibacter ruminantium. This project aimed to assemble a collection of phages to be employed in phage therapy. A range of animal-derived and environmental source samples were tested using culture-based methodology, however no lytic phages of methanogens were isolated. Given the dearth of knowledge regarding phages of rumen methanogens, this project established that these naturally-occurring phages may be present in very low concentrations within the rumen and this will need to be considered in future methanogen-phage isolation investigations. The project has begun the process of developing and adapting new methodologies for detecting and examining these phages

Resistance to root-lesion Nematodes for development of molecular markers

This is a sub-project of the Australian Wheat and Barley Molecular Marker Program funded by GRDC and led by Drs Diane Mather and Ken Chalmers of University of Adelaide. In this sub-project we will supply phenotypic data on resistance to two species of root-lesion nematodes (Pratylenchus thornei and P. neglectus) on several populations of wheat doubled haploids. We will also supply existing genotypic data on one doubled haploid population. We will also test one population of doubled haploids (CPI133872/Janz) a second time for resistance to P. thornei and P. neglectus and supply this information to University of Adelaide for the development of molecular markers for use by wheat breeders in selecting for resistance to root-lesion nematodes.

Variation in the hindgut microbial communities of the Florida manatee, Trichechus manatus latirostris over winter in Crystal River, Florida

The Florida manatee, Trichechus manatus latirostris, is a hindgut-fermenting herbivore. In winter, manatees migrate to warm water overwintering sites where they undergo dietary shifts and may suffer from cold-induced stress. Given these seasonally induced changes in diet, the present study aimed to examine variation in the hindgut bacterial communities of wild manatees overwintering at Crystal River, west Florida. Faeces were sampled from 36 manatees of known sex and body size in early winter when manatees were newly arrived and then in mid-winter and late winter when diet had probably changed and environmental stress may have increased. Concentrations of faecal cortisol metabolite, an indicator of a stress response, were measured by enzyme immunoassay. Using 454-pyrosequencing, 2027 bacterial operational taxonomic units were identified in manatee faeces following amplicon pyrosequencing of the 16S rRNA gene V3/V4 region. Classified sequences were assigned to eight previously described bacterial phyla; only 0.36% of sequences could not be classified to phylum level. Five core phyla were identified in all samples. The majority (96.8%) of sequences were classified as Firmicutes (77.3 ± 11.1% of total sequences) or Bacteroidetes (19.5 ± 10.6%). Alpha-diversity measures trended towards higher diversity of hindgut microbiota in manatees in mid-winter compared to early and late winter. Beta-diversity measures, analysed through permanova, also indicated significant differences in bacterial communities based on the season.

Managing cattle grazing intensity: effects on soil organic matter and soil nitrogen

Extensive cattle grazing is the dominant land use in northern Australia. It has been suggested that grazing intensity and rainfall have profound effects on the dynamics of soil nutrients in northern Australia’s semi-arid rangelands. Previous studies have found positive, neutral and negative effects of grazing pressure on soil nutrients. These inconsistencies could be due to short-term experiments that do not capture the slow dynamics of some soil nutrients and the effects of interannual variability in rainfall. In a long-term cattle grazing trial in northern Australia on Brown Sodosol–Yellow Kandosol complex, we analysed soil organic matter and mineral nitrogen in surface soils (0–10 cm depth) 11, 12 and 16 years after trial establishment on experimental plots representing moderate stocking (stocked at the long-term carrying capacity for the region) and heavy stocking (stocked at twice the long-term carrying capacity). Higher soil organic matter was found under heavy stocking, although grazing treatment had little effect on mineral and total soil nitrogen. Interannual variability had a large effect on soil mineral nitrogen, but not on soil organic matter, suggesting that soil nitrogen levels observed in this soil complex may be affected by other indirect pathways, such as climate. The effect of interannual variability in rainfall and the effects of other soil types need to be explored further.