An analysis of the outer membrane of desulfovibrio vulgaris (Woolwich)
D.vulgaris (Woolwich) OMs can be extracted successfully and reproducibly from the cell envelopes by the selective solubilisation of cell membranes by sarkosyl. Three Omps (Omps 1, 2 & 3) occur consistently in the OMs of C-Fe, NC & C+Fe cells. NC C+Fe OMs have, in addition, minor proteins absent from C-Fe OMs. Omp2 band is seen to be enhanced in C-Fe and NC OMs as indicated by PAGE. PAGE-immunoblotting of LPS indicates heterogeneity of these molecules. Immunological analyses of NC, C-Fe & C+Fe cells using specific antisera indicate no differences among these cell-types. Neither are antigenic differences revealed by further analyses of OM Western blots by specific antisera. However, pyrolysis analyses indicate that the cell-types analyses show variations in the cell ability of this technique to bacterial species cultured under different growth conditions indicates its potential as a tool for numerical taxonomy of the sulphate reducers. D.vulgaris (Woolwich) does not produce extra Omps in response to iron deprivation. Instead, it increases the synthesis of 0mp2 and LPS in its OM as reflected in the OM PAGE pattern and increased yields of LPS extracted from C-Fe cultures. HPLC sugar analyses indicate the LPS contain N-glucosamine, possibly rhamnose and an unidentified sugar. A change in HPLC sugar pattern of the C+Fe LPS samples indicates interactions between Fe(II) and LPS. This interaction is substantiated by X-ray microanalysis of the elemental content extracted LPS. The evidence indicates that LPS may be involved in Fe(II) uptake by the cells. LPS also takes part in the adhesion of D.vulgaris (Woolwich) to mild steel surfaces. This is demonstrated by the data from experiments using anti-LPS Fab fragments. The presence of these antibodies reduces the number of cells adhering to mild steel coupons. Fe-radiolabelling of OM components immobilised on nitrocellulose shows that Omps 1, 2 & 3 bind Fe(II). Blocking experiments using copper & magnesium indicate Omp1 to be Fe(II) specific while Omps 2 3 are not. The enhancement of Omp2 observed in C-Fe NC OMs in PAGE analyses indicates Omp2 to be principal cation binder, whose synthesis is increased under iron deprivation.
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