PMID:16677297

Citation	Mazza, P, Noens, EE, Schirner, K, Grantcharova, N, Mommaas, AM, Koerten, HK, Muth, G, Flärdh, K, van Wezel, GP and Wohlleben, W (2006) MreB of Streptomyces coelicolor is not essential for vegetative growth but is required for the integrity of aerial hyphae and spores. Mol. Microbiol. 60:838-52
Abstract	MreB forms a cytoskeleton in many rod-shaped bacteria which is involved in cell shape determination and chromosome segregation. PCR-based and Southern analysis of various actinomycetes, supported by analysis of genome sequences, revealed mreB homologues only in genera that form an aerial mycelium and sporulate. We analysed MreB in one such organism, Streptomyces coelicolor. Ectopic overexpression of mreB impaired growth, and caused swellings and lysis of hyphae. A null mutant with apparently normal vegetative growth was generated. However, aerial hyphae of this mutant were swelling and lysing; spores doubled their volume and lost their characteristic resistance to stress conditions. Loss of cell wall consistency was observed in MreB-depleted spores by transmission electron microscopy. An MreB-EGFP fusion was constructed to localize MreB in the mycelium. No clearly localized signal was seen in vegetative mycelium. However, strong fluorescence was observed at the septa of sporulating aerial hyphae, then as bipolar foci in young spores, and finally in a ring- or shell-like pattern inside the spores. Immunogold electron microscopy using MreB-specific antibodies revealed that MreB is located immediately underneath the internal spore wall. Thus, MreB is not essential for vegetative growth of S. coelicolor, but exerts its function in the formation of environmentally stable spores, and appears to primarily influence the assembly of the spore cell wall.
Links	PubMed Online version:10.1111/j.1365-2958.2006.05134.x
Keywords	Bacterial Proteins/analysis; Bacterial Proteins/genetics; Bacterial Proteins/physiology; Cell Wall/genetics; Cell Wall/ultrastructure; Gene Deletion; Gene Order; Green Fluorescent Proteins/analysis; Green Fluorescent Proteins/genetics; Hyphae/chemistry; Hyphae/physiology; Hyphae/ultrastructure; Microfilament Proteins/analysis; Microfilament Proteins/genetics; Microfilament Proteins/physiology; Mutation; Polymerase Chain Reaction; Recombinant Fusion Proteins/analysis; Recombinant Fusion Proteins/genetics; Spores, Bacterial/chemistry; Spores, Bacterial/physiology; Spores, Bacterial/ultrastructure; Streptomyces coelicolor/chemistry; Streptomyces coelicolor/physiology; Streptomyces coelicolor/ultrastructure
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STRCO:Q9L1G6		GO:0043934: sporulation	ECO:0000315:		P		Table 2. Average values of spore length and width of spores in chains of M145, MreB-depleted strains, complemented mutants and mre-IM complemented with the mreB–egfp fusion gene. "Mutational analysis clearly demonstrated that MreB in S. coelicolor is required for correct sporulation, and appears to affect spore wall formation. The aerial hyphae and spores of the mreB deletion mutant were swollen (Fig.4; Table 2), spores were sensitive to heat and treatment with SDS (Fig. 6), and irregularities in the spore cell walls were observed using TEM (Fig. 5B)."	complete
STRCO:Q9L1G6		GO:0010286: heat acclimation	ECO:0000315:		P		Fig. 6. Effect of the mreB mutation on resistance of the spores to heat treatment.	complete
STRCO:Q9L1G6		GO:0031160: spore wall	ECO:0000314:		C		Fig. 7 (F). Localization of the MreB–EGFP fusion protein during morphological differentiation.	complete
STRCO:Q9L1G6		GO:0000902: cell morphogenesis	ECO:0000315:		P		Fig. 1. Lethal effect of MreB overexpression on solid growth. Fig. 4. Effect of mreB deletion on morphological differentiation. Fig. 5. Transmission electron micrographs of the mreB mutant.	complete

References

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