Abstract
Anabaena sp. PCC 7120 is a filamentous cyanobacterium able to fix atmospheric nitrogen in semi-regularly spaced heterocysts. For correct heterocyst function, a special cell envelope consisting of a glycolipid layer and a polysaccharide layer is essential. We investigated the role of the genes hgdB and hgdC, encoding domains of a putative ABC transporter, in heterocyst maturation. We investigated the subcellular localization of the fusion protein HgdC-GFP and followed the differential expression of the hgdB and hgdC genes during heterocyst maturation. Using a single recombination approach, we created a mutant in hgdB gene and studied its phenotype by microscopy and analytical chromatography. Although heterocysts are formed in the mutant, the structure of the glycolipid layer is aberrant and also contains an atypical ratio of the two major glycolipids. As shown by a pull-down assay, HgdB interacts with the outer membrane protein TolC, which indicates a function as a type 1 secretion system. We show that the hgdB-hgdC genes are essential for the creation of micro-oxic conditions by influencing the correct composition of the glycolipid layer for heterocyst function. Our observations confirm the significance of the hgdB-hgdC gene cluster and shed light on a novel mode of regulation of heterocyst envelope formation.
Highlights
IntroductionThey inactivate oxygenic photosynthesis and increase the respiration rate to remove oxygen and to meet the demand of the nitrogenase for energy
The group of Peter Wolk identified a gene island that comprises several genes involved in hgl layer formation
Transposon mutants in a gene island that comprises several genes involved in hgl layer formation
Summary
They inactivate oxygenic photosynthesis and increase the respiration rate to remove oxygen and to meet the demand of the nitrogenase for energy. Morphological changes precede these metabolic alterations, especially the early formation of an additional cell envelope, which protects these cells from environmental oxygen. This special envelope consists of two layers: the outer exo-polysaccharide layer (hep layer) and the inner laminated glycolipid layer (hgl layer). The hgl layer is the actual barrier for gases, including oxygen, while the outer hep layer mechanically protects the subjacent hgl
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
