Functions and biosynthesis of a tip-associated glycan in Streptomyces
- X. Zhong
- Wednesday 29 March 2023
2311 GJ Leiden
- Prof. D. Claessen
Streptomycetes are soil-dwelling Gram-positive bacteria and can produce clinical drugs and adapt to environmental fluctuations through diverse morphological changes. The morphological development of streptomycetes features apical growth, which is determined by a tip-organizing center containing machinery for the synthesis of a cellulose-like glycan deposited at the cell surface.
This thesis demonstrated that the cellulose-like glycan likely cellulose and the related synthesis machinery are unique in comparison with other Gram-negative cellulose synthesis systems. It showed that the synthesis of this glycan is performed by the glycosyltransferase ClsA and matured galactose-oxidase protein GlxA, in which these two proteins form a stable complex determined by electron microscope and can synthesize cellulose with UDP-Glucose in vitro. Subsequently, the lytic polysaccharides monooxygenase LpmP and the glucanase ClsZ, adjacent to CslA/GlxA, cooperatively cleave peptidoglycan and create a passage to assist the exposure of this glycan on cell surface. In addition, this thesis further showed that the cellulose-like glycan of Streptomyces coelicolor is responsible for the aggregation of clumps, which is distinct from Streptomyces lividans where this glycan mediates germlings’ aggregation.
Besides the cellulose biosynthesis machinery, Streptomyces tip-organizing center also contains a peptidoglycan synthase, cytoskeleton proteins and other determinants. This thesis also revealed coordination of these determinants is performed by a stomatin-like protein StlP, which locates in the same gene cluster with CslA/GlxA/CslZ/LpmP. Oligomerization of StlP forms a fluid microdomain at hyphal tips, which spatially confines the whole tip organizing center. The findings of this thesis contribute to a better understanding of polar growth in streptomycetes.
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