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Title: Metabolism of dimethyl disulphide, carbon disulphide and other volatile sulphur compounds by chemolithoautotrophic sulphur bacteria
Author: Smith, Neil A.
ISNI:       0000 0001 3453 0147
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1988
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The isolation of a number of strains of bacteria able to grow on dimethyl disulphide (DMDS) and dimethyl sulphide (DNS) as sole sources of energy is described. The isolates came from diverse habitats including soil, peat, marine mud and a freshwater pond, and were morphologically and physiologically best described as thlobacilli capable of growth as Calvin cycle autotrophs on inorganic sulphur compounds, methylated sulphides or thiocyanate. One Isolate (E6) was examined in detail and analysis of its DNA showed a mean mol% G - C content of 60.5 ± 1.0 which is In the normal range of f. thioparua. Substrate oxidation kinetics indicated that methanethiol (NT), sulphide, formaldehyde and formate could be implicated as intermediates in DNDS metabolism. Growth yields in chemostat culture on DMDS Indicated that energy conservation was probably coupled to the oxidation of formaldehyde and sulphide (derived from DMDS via NT) to CO and sulphide. Further evidence for the proposed oxidation pathway of DMDS was provided by demonstration of activities of a previously uncharacterised NADH-dependent DMDS 'reductase', NT oxidase, catalase, MAD4-dependent formaldehyde and formate dehydrogenases, rlbulose 1,5 - blsphosphate carboxylase and a sulphide oxidising system. This is the first demonstration of the Isolation of organisms into pure culture that are capable of growth on DMDS as sole energy substrate. T. thioparua strain Tk-m was found to be capable of growth on carbon disulphide (CS2) and carbonyl sulphide (COS). During growth on CS2, GC/MS analysis of the chloroform-extractable volatiles from the culture medium showed the formation of COS as a transient intermediate In CS2 metabolism. Anaerobic Incubation of call suspensions with CS2 also showed the production of hydrogen sulphilde (H2S) into the headspace. The proposed pathway of CS2 metabolism by T. thioparua strain TK-m most likely involved its reductive cleavage to COS and »¿S, COS then undergoin3 similar hydrolysis to CO- and HjS. This serves as the first detailed study of microbial CS2 metabolism.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology