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Title: The role of the intra-cytoplasmic membrane system in photosynthesis and differentiation in Rhodomicrobium vannielii
Author: Kelly, David Jacob
ISNI:       0000 0001 3596 625X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1985
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Intra-cytoplasmic membranes were isolated from Rhodomicrobium vannielii . a Bchla containing member of the Rhodospirillaceae which exhibits extensive cellular differentiation, in order to probe the composition and organization of the photosynthetic apparatus. Detergent solubilization of ICM followed by gel electrophoresis or sucrose gradient centrifugation led to the isolation of two native pigmented complexes, the major one (B800-865) identifiable with the "accessory" light-harvesting complex II found in other members of the Rhodospirillaceae. The minor complex (B885-RC) contained both reaction centre and light harvesting Bchl and was unusual in containing a c-type cytochrome (c- 553) bound to the 31,000 M subunit of the reaction centre. Bioenergetic studies of the B885-RC complex reconstituted into liposomes showed the c-553 to be an electron donor to the RC in vitro. These properties are somewhat similar to those of the Bchlb containing Rp. viridis but unlike many Bchla containing Rhodospirillaceae. The synthesis of the photosynthetic pigment protein complexes in vivo was found to be regulated by oxygen and light but the composition of the photosynthetic apparatus was the same in both swarmer cells and multicellular arrays. However, ICM prepared from pulse-labelled swarmer cells undergoing selection synchronized growth and differentiation showed distinct changes in the pattern of proteins synthesised at different stages during the cell-cycle. During differentiation, the B885-RC pigment- protein complex was only synthesised during daughter cell formation when de novo production of new ICM is necessary. These observations were correlated with the obligate polar growth pattern of this microbe. The production of a 34,000 M protein identified as flagellin was also modulated during the cell-cycle, with synthesis being restricted to the swarmer cell. Surprisingly, however, few changes in penicillin-binding proteins (PBPs) in cell-free extracts could be detected during the cell- cycle but the pattern of PBPs in Rm. vannielii was characterised by high M species unlike those of Rb. sphaeroides. the only other photosynthetic bacterium examined in this respect to date. Bioenergetic studies concerning the cell-cycle were hampered by remarkable permeability properties that did not allow the use of probe ions for Δ Ψ and Δ pH. However, using the electrochromic response of the endogenous carotenoids an overall decrease in Δ Ψ during differentiation was observed but the reasons for this were unclear.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH Natural history ; QK Botany ; QR Microbiology