- Volume 135, Issue 2, 1989

Iron reduction and uptake was studied in wild-type and haem-deficient strains of Saccharomyces cerevisiae. Haem-deficient strains lacked inducible ferri-reductase activity and were unable to take up iron from different ferric chelates such as Fe(III)-citrate or rhodotorulic acid. In contrast, ferrioxamine B was taken up actively by the mutants as well as by the wild-type strains. At a low extracellular concentration, uptake was insensitive to ferrozine and competitively-inhibited by Ga(III)-desferrioxamine B. Extracellular reductive dissociation of the siderophore occurred at higher extracellular concentrations. Two mechanisms appear to contribute to the uptake of ferrioxamine B by S. cerevisiae: one with high affinity, by which the siderophore is internalized as such and another with lower affinity by which iron is dissociated from the ligand prior to uptake.

A Streptomyces sp. isolated from compost degraded the hemicellulose fraction of straw efficiently but apparently not native cellulose. Ball-milled straw induced endoglucanase, β-glucosidase, β-xylanase and β-xylosidase. Carboxymethylcellulose, cellotetraose and cellotriose induced cellulolytic enzymes specifically whereas cellobiose acted as inducer for β-glucosidase only. Cellotriose and cellotetraose induced β-glucosidase, but only partially induced endoglucanase. Hemicellulose (in the form of xylan) and xylobiose induced only β-xylanase and β-xylosidase. Kraft lignin and syringic acid induced β-xylanase and endoglucanase but not the other enzymes. 3,4-Dimethoxycinnamic acid slightly induced β-xylanase whereas 3,5-dimethoxy-4-hydroxycinnamic acid specifically induced endoglucanase. Neither veratric acid nor vanillic and ferulic acids induced any of the cellulolytic or hemicellulolytic enzymes. Enzyme production was subject to a form of carbon catabolite repression. Endoglucanase and β-xylanase were excreted into the culture medium. Four protein components, one acidic (pI 5·2) and three basic (pI 8·15, 8·45 and 8·65) exhibited β-xylanase activity. Two acidic components (pI 3·55 and 3·75) displayed endoglucanase activity.

The phosphate regulation and subcellular location of the hydrolytic enzyme alkaline phosphatase were investigated in the Gram-negative bacterium Zymomonas mobilis. The biosynthesis of alkaline phosphatase was not derepressed at a low phosphate concentration as is generally observed in other micro-organisms, nor was it repressed by high phosphate concentrations in the medium. The enzyme level was rather constant during the growth phases in batch culture, at a value at least 8.4-fold lower than that observed in Escherichia coli. The alkaline phosphatase of Z. mobilis was found associated with the membrane fraction after cell disruption, osmotic shock treatment or spheroplast formation. This is a rather unusual location, since most of the alkaline phosphatases from Gram-negative bacteria have been shown to be periplasmic enzymes. Activity staining on polyacrylamide gels after two-dimensional electrophoresis revealed two isoforms of alkaline phosphatase, each of approximate molecular mass 56 kDa. These two forms belong to a group including the more basic envelope proteins of Z. mobilis. Our results indicate that the enzyme from Z. mobilis differs markedly from typical alkaline phosphatases of other Gram-negative bacteria.

Surface washings were prepared from cultures of fungi grown on agar slants and the wash components were fractionated by gel-filtration HPLC. A range of low-M r glycoproteins (< 10000) were detected in all the washes, and in some species several high-M r glycoprotein components (> 150000) were also present. The HPLC analyses indicated species-specific different in the profiles. Regions of specific antigenicity within profiles were detected by monoclonal antibodies.

Localization of nitrogenase, glutamine synthetase (GS), phycoerythrin (PE) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was studied with immunocytochemical techniques in the cyanobiont and the free-living cultured isolate Nostoc 7801 of Anthoceros punctatus. In both cases nitrogenase was located in heterocysts only and was uniformly distributed within the cell. GS was located both in heterocysts and vegetative cells, with a uniform cellular distribution in each cell type. Whereas heterocysts of Nostoc 7801 had about twofold higher label than vegetative cells, labelling in heterocysts and vegetative cells of the cyanobiont was similar. While the GS content of the vegetative cells of the cyanobiont and Nostoc 7801 was comparable, the apparent GS content of the cyanobiont heterocysts was 60% less than that in Nostoc 7801 heterocysts. PE and RuBisCO were located in vegetative cells only. PE was located on thylakoid membranes and RuBisCO in the cytoplasm and carboxysomes. In each case the pattern of labelling in the cyanobiont and Nostoc 7801 was similar.

The growth factor requirements and other properties of two strains of avian haemophili, labelled as ‘Haemophilus gallinarum’(an X- and V-factor-dependent organism) and stored since the 1940s and 1950s, were examined. Both strains were X-factor independent and V-factor dependent and possessed the typical biochemical serological and pathological properties of H. paragallinarum. In experiments repeating the tests used in the 1930s that reported the existence of X- and V-factor-dependent avian haemophili, we found that the methodology used resulted in reference strains of H. paragallinarum (X-factor independent and V-factor dependent) appearing to be X- and V-factor dependent. It is likely that the early descriptions of the aetiological agent of infectious coryza as an X- and V-factor-dependent organism were incorrect.