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Title: Cellular growth of the Actinomycete Streptomyces coelicolor
Author: Gray, D. I.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1987
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Apical growth of Streptomyces coelicolor was investigated by determining the gradient of wall incorporation within the hyphal extension zone. Wall rigidification was envisaged to occur by secondary cross-linking during a `remodelling' process. Hyphal tip shape approximated more closely to half ellipsoids of revolution and was mathematically described by fitting polynomials. The surface tension varied as a function of the distance from the tip within the extension zone, and the validity of Koch's surface stress theory was assessed. Hyphal morphology was altered using wall loosening agents which interfered with wall rigidification processes. DNA or RNA synthesis was not restricted to any particular region of the hypha. Nucleoid segregation occurred mainly within the marginal region and appeared to be a random process, but away from the margin nucleoid aggregations formed as segregation ceased. Inhibition of protein synthesis stopped hyphal elongation but DNA and peptidoglycan synthesis continued. The distribution of nucleoids within substrate hyphae was studied and aggregated nucleoids were found to occur non-randomly along hyphae, and appeared to be associated with branching points. The size of the smallest staining nucleoids and the average length of cytoplasm per nucleoid were determined. Cytological staining of hyphal and cross-walls was largely unsuccessful, but a method was found to demonstrate the positions of septa within the primary mycelium. The significance of the observations is discussed in the light of the fixation and other preparative steps used. Micromorphology analysed by thin sections was found to be similar to that reported previously. Aged liquid cultures were investigated by transmission and scanning electron microscopy and alterations to the normal hyphal morphology were attributed to stalling effects within the culture. Measurements of hyphal characteristics showed that some of these measured features did not vary significantly with time, while others could be related to the development of the mycelium. Septation was found not to determine the site of branching along hyphae, while branch diameter was related to branching order. A model for the growth of substrate hyphae was developed based upon the investigations performed using histological, micromorphological and mycelial developmental analysis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available