ALBERT

Notes: Abstract 1) Rhodobacter capsulatus (formerly Rhodopseudomonas capsulata) strain 37b4 was subjected to transposon Tn5 mutagenesis. 2) Kanamycin-resistant transconjugants were screened for their inability to reduce trimethylamine-N-oxide (TMAO) as judged by the lack of alkali production during anaerobic growth on plates containing glucose as carbon source and cresol red as pH indicator. 3) Of 6 mutants examined, all were found to have considerably decreased levels of methylviologen-dependent TMAO reductase activity and dimethylsulphoxide (DMSO) reductase activity. 4) Periplasmic fractions of one of these mutants (DK9) and of the parent strain were subjected to sodium dodecylsulphate polyacrylamide gel electrophoresis. The gels were stained for TMAO-reductase and DMSO-reductase. With the wild-type strain, only a single polypeptide band, Mr=46,000, stained for TMAO and DMSO reductase activity. In mutant DK9 this band was not detectable. 5) In contrast to the parent strain, harvested washed cells of mutant DK9 were unable to generate a cytoplasmic membrane potential in the presence of TMAO or DMSO under dark anaerobic conditions. 6) In contrast to the parent strain, DK9 was unable to grow in dark anaerobic culture with fructose as the carbon source and TMAO as oxidant.

Notes: Abstract The effects of various electron transport inhibitors upon the rates of reduction NO 3 - , dimethyl sulphoxide (DMSO) and N2O in anaerobic suspensions of Rhodobacter capsulatus have been studied. A new method for the determination of the rates of reduction of these auxiliary oxidants in intact cells is presented, based on the proportionality observed between the concentration of oxidant and the duration of the electrochromic carotenoid bandshift. For NO 3 - and N2O good agreement was found between rates of reduction determined using electrodes and those determined by the electrochromic method. Myxothiazol and antimycin A had no effect on the rates of reduction of NO 3 - and DMSO suggesting that the cytochrome b/c 1complex is not involved in electron transport to these oxidants. 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) inhibited at two sites, one within the cytochrome b/c 1complex and the other on the nitrate reducing pathay, but had no effect on electron transport to N2O or DMSO. In both intact cells and cell free extracts, HOQNO had no effect on the nitrate dependent re-oxidation of reduced methylviologen (MVH2), a direct electron donor to nitrate reductase. Our data are consistent with a branch point for the auxiliary electron transport pathways at the level of the ubiquinone pool.

Notes: Abstract The biodiversity of the Cape Peninsula (49127 ha in extent) has been considerably affected by various factors since European settlement in 1652. Urbanization and agriculture have transformed 37% of the original area of natural vegetation. Lowland vegetation types have been worst affected, with almost half of the transformation occurring in one of the 15 recognized vegetation types. Vegetation at high altitudes has been little affected by urbanization and agriculture, but alien trees and shrubs are now threatening biodiversity in these areas. Of the area not affected by urbanization and agriculture 10.7% is currently under dense stands (〉25% canopy cover) of alien plants and another 32.9% is lightly invaded. Dense stands of Acacia cyclops, the most widespread invader, cover 2510 ha, 76% of the total area under dense alien stands. This paper assesses the impacts of these factors on aspects of the plant biodiversity of the area, namely, the distribution of major vegetation types and of endemic, rare and threatened plant taxa and of taxa in the Proteaceae (a prominent element in almost all communities, taken as an indicator of overall plant biodiversity). Possible future impacts on biodiversity are assessed by considering the effects of several scenarios involving increased urbanization and changes to alien plant control strategies and further spread over the next 50–100 years. The worst-case scenario for urbanization sees the area under natural vegelation reduced to 12163 ha (39.3% of its extent in 1994, or 24.8% of its original extent). Under this scenario almost a quater of the 161 endemic, rare and threatened (‘special’) taxa are confined totally to urban areas; 57.4% of the known localities of these taxa, and 40.1% of the remaining localities of Proteaceae taxa are transformed. Dense alien stands currently affect 29.8% of the localities of special taxa known from herbarium records and 8.4% of these taxa currently occur only in areas at present affected by aliens. Clearing all dense stands would result in 62.9% of special taxa having less than half of their known localities affected (49.1% at present). Under this scenario, 92% of Proteaceae taxa have more than 75% of their localities unaffected by aliens. If clearing is confined to specific areas (the Cape Peninsula Protected Natural Environment or all publicly-owned land) and the aliens spread further outside these areas, the area of natural vegetation remaining shrinks (to 82.4% of the current extent if control is confined to public land). The further losses in biodiversity associated with these scenarios are described. If control programmes collapse and all potentially invadable land is occupied by dense alien stands, only 407 ha of natural vegetation would remain (1.5% of the current extent). The probability of the various scenarios materializing is discussed. To minimize further losses in biodiversity it is essential that: (1) a major initiative is launched immediately to clear (firstly) the 10184 ha of lightly invaded vegetation and then the 3313 ha of densely invaded vegetation; (2) no urban development be permitted within the boundaries of the Cape Peninsula Protected Natural Environment; (3) a systematic programme of prescribed burning (linked to the alien control programme) is initiated; and (4) contingency measures are implemented to improve the status of seriously threatened taxa, habitats and vegetation types.