Challenges of heterotrophic bacteria in the Southern Ocean
An exploration of tools to investigate the response of heterotrophic bacteria to nutrient limitation
Morgan Hartley, Professional Practice 2020, Laboratory of microbial oceanography
Background
The Southern Ocean is well known for its iron limitation, which poses a challenge for the organisms which rely on this trace metal. It is well know that iron limitation negatively effects the phytoplankton communities in within the Southern Ocean, but how does this limitation effect bacterial communities? Do bacterial communities need iron to survive?
Throughout my professional practice I learnt different analytical methods for exploring differences in bacterial communities. In this website I provide multiple examples of ways in which you can investigate responses of bacterial communities to changes in nutrient availability!
What are heterotrophic bacteria?
The term 'Heterotroph' refers to the organisms ability to utilise carbon. Heterotrophic bacteria utilise carbon as their primary energy source. The image to the right shows two different species of heterotrophic bacteria.
Left: Bacteria species of the SAR11 clade.
Right: Bacteria species of the family Microbacteriaceae.
Do they hold an important role in our Oceans?
Yes! Microorganisms are the most abundant organisms in the ocean! Heterotrophic bacteria hold a central role in the many of the oceans important biogeochemical cycles.
This figure shows the different regions of the Southern Ocean (SO). The SO is a very interesting experimental sight due to the nutrient limitation. In most of the SO iron is a limiting nutrient, but in the wake of islands natural iron fertilisation can lead to increased phytoplankton and bacterial activity.
Image: Wilkins, D., Yau, S., Williams, T.J., Allen, M.A., Brown, M.V., DeMaere, M.Z., Lauro, F.M. and Cavicchioli, R., 2013. Key microbial drivers in Antarctic aquatic environments. FEMS Microbiology Reviews, 37(3), pp.303-335.
Is iron important for their success?
Yes! The primary role of iron (Fe) in heterotrophic bacteria is in the microbial respiratory system, due to the importance of Fe-containing enzymes. This means that the overall energy transfers within bacteria can be seriously effected by limitations in iron.
Most species of marine heterotrophic bacteria are no bigger than 1 micrometres (µm), making all species very difficult to see with the naked eye. To find out more about how we study these tiny organisms click on this white box!
