Nutrient-Starvation-Induced Acclimation Processes and Cell Differentiation in Cyanobacteria

Karl Forchhammer

KarlForchhammer Jan19red 01
  • PhD in microbiology, LMU Munich, 1990
  • Postdoctoral training at the LMU Munich and Institut Pasteur, Paris
  • Group leader at the LMU Munich and Justus Liebig-University Giessen, 1999-2007
  • Head of the Department of Microbiology/Organismic Interactions, University of Tübingen since 2007

Research Interest

Cyanobacteria are oxygenic photosynthetic bacteria and dominant primary producers occurring in almost all illuminated habitats. Therefore, they play pervasive roles in global carbon-, nitrogen- and oxygen-cycles on earth. They evolved under a “feast and famine” regime, whereby periods of fast growth, as it occurs for example during bloom formation, may cause growth-limiting nutrient depletion. As a consequence, they need to adapt to starvation conditions until nutrients are replenished and vegetative growth can resume. The associated life-style switches require a highly coordinated re-wiring of cellular activities. The molecular mechanisms underlying this flip-flopping between vegetative growth and metabolic quiescence are in the centre of our research interest.

Our studies, which address fundamental molecular processes at the systems levels as well as on particular layers such as the regulation of pathway activities and nutrient-specific signal transduction events are mostly performed with the cyanobacterium Synechocystis PCC 6803. We use the acclimation to nitrogen starvation as an experimental model system for a simple developmental program that allows survival in a dormant state for extended periods of times. Therefore, we employ state-of-the-art molecular biology and cell biology methods in combination with molecular genetics and physiology.

  • Forchhammer Chlorosis
    click to enlarge

Life-style switch of Synechocystis cells imposed by changing ambient nitrogen supply: when vegetative growing cells (left) are exposed to nitrogen starvation, the cells undergo chlorosis. When chlorotic dormant cells (right) are provided with nitrogen, they awake and re-enter vegetative growth.

Available PhD Projects

No projects offered in this selection.

Selected Reading

1) Klotz A, Georg J, Bucinska L, et al. Forchhammer, K. (2016). Awakening of a dormant cyanobacterium from nitrogen chlorosis reveals a genetically determined program. Curr Biol 26, 2862-2872.

2) Spät P, Klotz A, Rexroth S, Maček B and Forchhammer, K (2018).  Chlorosis as a developmental program in cyanobacteria: the proteomic fundament for survival and awakening. Mol Cell Proteomics doi: 10.1074/mcp.RA118.000699

3) Forchhammer K. and Schwarz R (2018). Nitrogen chlorosis in unicellular cyanobacteria – a developmental program for surviving nitrogen deprivation. Environmental Microbiol. doi.org/10.1111/1462-2920.14447