Title: Intracellular accumulation of soluble substrates in bacteria – a novel storage strategy in dynamic environments

Many microorganisms in nature live under dynamic conditions with continuous changes in organic substrates, electron acceptors (e.g. oxygen and nitrate) and nutrients (e.g. phosphorus, P). A common strategy among bacteria growing in gradients or dynamic systems is to be very versatile in substrate uptake and/or to take up large amounts of substrates and store them for later use. Well-known examples are uptake of organic substrate and subsequent intracellular conversion to polyhydroxyalkanoates (PHA), glycogen or lipids. The ability to store carbon for later use provides the bacteria with great competitive advantages in systems where nutrient levels fluctuate. In this project, we will investigate a novel mechanism for microbial intracellular storage of substrate in dynamic anaerobic/aerobic systems, namely anaerobic accumulation of un-metabolized organic ions (acetate and glycine) in certain Gram-positive bacteria.

Funding

The project is funded by The Danish Council for Independent Research (FNU) in the period 2014-2017.

Project content

1. Intracellular substrate accumulation in Tetrasphaera elongata. It is the aim to understand how T. elongata accumulates, stores and oxidizes acetate and selected amino acids under anaerobic/aerobic conditions, and to develop a comprehensive metabolic model.
2. Time resolved substrate uptake in T. elongata by on line detection. It is the aim to investigate the initial capacity for uptake and storage of acetate and glycine under an anaerobic perturbation and to detect initial stages of substrate utilization – both under anaerobic and aerobic conditions.
3. Screening of accumulation capabilities in other Gram positive bacteria. It is the aim to screen other potential candidate bacterial isolates for the capability to uptake, store and oxidize intracellular organic acetate and glycine under anaerobic-aerobic conditions.
4. Intracellular substrate accumulation in enriched cultures of Tetrasphaera in situ. It is the aim to verify that uncultured Tetrasphaera accumulates, stores and oxidizes acetate and selected amino acids under anaerobic/aerobic conditions in situ, and to test the metabolic model developed for T. elongata.

Project participants

Aalborg University, Center for Microbial Communities:

• Per Halkjær Nielsen, Professor (project leader)
• Reinhard Wimmer, Professor
• Kåre Lehmann Nielsen, Associate professor
• Florian Herbst, Postdoc.

Collaboration

• Professor Dr. Michael Wagner, Department of Microbial Ecology, Univ. of Vienna
• Dr. Mathilde Lerche, Albeda Research, Copenhagen