Nitrogen chlorosis in unicellular cyanobacteria – a developmental program for surviving nitrogen deprivation

Karl Forchhammer, Rakefet Schwarz

Research output: Contribution to journalReview articlepeer-review

52 Scopus citations


Cyanobacteria evolved sophisticated mechanisms allowing them to cope with environmental depletion of combined nitrogen. Here, we describe progress in understanding the processes involved in acclimation of nondiazotrophic cyanobacteria to nitrogen shortage, known as nitrogen chlorosis. The process includes immediate metabolic changes and degradation of light harvesting complexes as well as long-term acclimation responses. Consequently, quiescent cells substantially differing from vegetative cells are obtained. Thus, the process leading to these considerable metabolic and morphological changes is referred to as a developmental program. Current understanding of the relevant regulatory processes depicts an intricate mechanism involving modulation of transcription activators by proteinaceous interacting components, as well as by small metabolites reporting the energy status and carbon–nitrogen balance of the cell. In addition, we describe in detail the quiescent state characterizing cells under prolonged starvation and the process of recovery from this dormant chlorotic state. Accumulated data provide an in depth understanding of the mechanisms accompanying the cycling of cyanobacterial cells between vegetative growth, the quiescent-state and the recovery program, allowing them to regain proliferative growth upon nutrient replenishment.

Original languageEnglish
Pages (from-to)1173-1184
Number of pages12
JournalEnvironmental Microbiology
Issue number4
StatePublished - Apr 2019

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© 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.


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