Page 103 - University of Pretoria Research Review 2017

Foreword
Introductory Messages
representatives (termed ‘microbial dark matter’, (Rinke et al., 2013)*. Attempts to characterise these microbial communities in the laboratory traditionally relied on culture-based molecular approaches that mimic environmental growth conditions (such as complex micronutrients). But such approaches are known to target only the fast-growing microorganisms whose nutritional and growth requirements are easily reproducible in laboratory settings.
The fairly recent advent of culture-independent approaches, which rely on detecting microorganisms by assaying their genes, has made possible the complete characterisation of microbial communities in complex environments. Such approaches have begun to reveal the true extent of microbial diversity and microbially- mediated functions in natural environments. Scientists are now beginning to understand the roles played by microbial communities in crucial ecosystem processes such as nutrient cycling, organic matter decomposition and carbon sequestration. Several recent studies have shown the complexity of ‘microbial dark matter’ and the importance of microorganisms in both terrestrial and marine ecosystems. However, we still have very limited understanding of the role of climatic factors as drivers of the abundance and diversity at regional and global scales. This is primarily due to the high levels
of microbial diversity and the fact that environmental variability such as temperature may shape community
abundance differently at different spatial scales. In marine ecosystems, the complexity associated with water masses and current properties may shape diversity and functionality differently in different oceans.
South Africa is surrounded by important marine ecosystems separating the cold South Atlantic waters from the warm Indian Ocean Agulhas Current along the East Coast. The Southern Ocean, located south
of 40 degrees of latitude, is a crucial component
of the global carbon cycle and is thought to take
up half of the atmospheric CO2 produced through anthropogenic activities. The past few decades of research in this ocean have provided new insights into the links between ocean-atmospheric physics and the availability of trace elements (such as iron, which are present at very low concentrations) in the Southern Ocean. These studies have shown, for instance, that
a limitation in iron and other trace metals impacts on the productivity of biological communities. However, these studies have largely focused on phytoplankton and macro-algal community composition and biomass. Despite the known importance of microorganisms in regulating biogeochemical cycling, surprisingly few studies have assessed microorganism community dynamics in this region.
* Rinke C et al. Insights into the phylogeny and coding potential of microbial dark matter. Nature, 499, 431.
DEVELOPMENT AND CHANGE
PEOPLE AND CONTEXTS
HEALTH AND WELL-BEING
PLANET AND SUSTAINABILITY
Microbial Ecology and Biodiversity
Awards
Lead Researchers
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Thulani Makhalanyane