Microbial diversity as a tool for
understanding ecosystem functioning
RA Dorrington
BACTERIA + ARCHAEA
ALGAE + FUNGI
PROTOXOA +WORMS
INVERTEBRATES
PLANTS
VERTEBRATES
RELATIVE SPECIES ABUNDANCE
BACTERIA + ARCHAEA
ALGAE + FUNGI
PROTOXOA +WORMS
INVERTEBRATES
PLANTS
VERTEBRATES
RELATIVE SPECIES ABUNDANCE
VIRUSES
~68 different viruses for every cellular species
Nutrient cycling in Antarctic and sub-Antarctic systems
o Simple systems, aabsence of grazing => energy and biomass is channelled into a detritus trophic pathway
o Dominated by microbes (< 1 µm) = bacteria, algae, fungi, protozoans and their viruses,
o Microbes are the principle drivers of nutrient cycling – carbon, nitrogen, sulphur
o Specialized communities => highly sensitive to environmental change
o E.g. increase in temperature => increase in soil respiration, shifts in nitrogen cycling1
1 Yargeua et al., 2012.
Microbes and ecosystem functioning
o Dominant taxa – total biomass, phylogenetic diversity and metabolic activity
o Regulating key biogeochemical processes - carbon, nitrogen, phosphate & sulphur cycles o Species diversity, population structure of
numerically dominant, metabolically active families of microbes = nutrient cycling and ecosystem
functioning
o Symbiotic and mutualistic associations with other organisms (e.g. invertebrates) nutritionally important for host survival
o Relative abundance of species - genetic barcoding (ribosomal RNA gene sequence)
o High throughput, cost-effective Next Generation Sequencing (NGS) technologies
o Bacteria, algae, fungi and protozoans from the same sample (~ 30 - 300 mg) – who’s there?
o Ability to identify metabolically active vs. dormant organisms – who’s doing the work?
o Metagenomic and metabolimic analysis – what kind of work?
Microbial diversity as a tool for
understanding ecosystem functioning
SANAP RESEARCH PROJECTS
o Microbes and ecosystem functioning PI: Rosie Dorrington (Rhodes)
Collaborative Projects
o Human impacts on Antarctic Biodiversity PI: Steven Chown ,(CIB)
o Landscape processes in Antarctic Ecosystems
PI: Ian Meiklejohn, ( Rhodes)
o South Atlantic Meridional Overturning Circulation SA (SAMOC-SA)
PI: Isabelle Ansorge (UCT)
o Majority of microbial diversity in marine environment are present at very low abundances - “Rare
species”
o Rare species may become abundant in response to environmental or habitat changes that provide
conditions that support rapid growth
o Consequences of global climate change are likely to have profound effects on the structure of marine
microbial populations and nutrient cycling.
Impact of Global Climate Change on Marine
Microbial populations?
RESEARCH QUESTIONS
o What role to microbes play in the functioning of sub-Antarctic terrestrial and marine
ecosystems?
o How will the microbial communities respond to global climate change?
o What will be the impact on these ecosystems?
PILOT STUDY OFF PRINCE EDWARD ISLAND
o Surveyed Archaea, Bacteria & Eukaryotes (<100µm)
~ 65 000 sequences
o Diversity & population structure of microbes n the water column - total cells vs. metabolically active o Seasonal variation in population structure &
metabolic activity - summer vs. winter
NEW RESEARCH QUESTIONS
o Is the population structure and metabolic activity of marine microbes in the Southern Ocean are distinct?
o And if so can changes in microbial
communities be used as a tool for modelling the impact of global climate change on
marine ecosystems
On Marion Island
Current research projects
Understanding the role of microbes as drivers of terrestrial nutrient cycling
o Pringleophagia marioni gut-associated microbiota
responsible for breakdown of plant material (cellulose) protein and chitin (other detritus)
What microbes are associated with larval guts
What role do they play in facilitating larval nutrition?
Does the gut microbial change when the host is stressed?
o Seasonal changes in soil microbial communities and their functioning in nutrient cycling
*
o What is the extent of microbial diversity and are there specialized communities in the different biomes on Marion Island
o How will these communities respond to climate change
o What will be the consequences for the
ecosystems that characterize these biomes?