ATP hydrolysis in a marine bacterium.

The membrane-bound adenosine triphosphatase of marine pseudomonad B-16, when solubilized, is able to rebind to depleted membrane residues of the bacterium and to those of Escherichia coli.     

Optimisation of somatic embryogenesis in fourteen cultivars of sweet potato [Ipomoea batatas (L.) Lam.]

Culture procedures have been developed to facilitate the induction and maintenance of somatic embryogenic tissues in 14 out of 16 tested cultivars of sweet potato [Ipomoea batatas (L.) Lam]. Both the size of the axillary bud explant and the type of auxin were found to be critical for the successful induction of somatic embryogenesis. Of the five auxins screened 2,4-dichlorophenoxyacetic acid 2,4-D and 2,4,5-trichlorophenoxyacetic acid were the most effective, with use of the latter inducing the production of embryogenic tissues in 7 cultivars which responded poorly or not at all to 2,4-D. Procedures for secondary/cyclic embryogenesis, formation of mature embryos and their conversion to plants are also described. Received: 24 September 1996 / Revision received: 16 December 1996 / Accepted 27 January 1997     

Cryopreservation of embryogenic tissue of a range of genotypes of sweet potato (Ipomoea batatas [L] Lam.) using an encapsulation protocol

Embryogenic tissue of nine sweet potato [Ipomoea batatas (L.) Lam] genotypes from Asia, Africa and the Americas was established from in vitro axillary buds on Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid or 2,4,5-trichlorophenoxyacetic acid. Embryogenic aggregates, 1.0–2.0 mm in diameter, were encapsulated in alginate gel, precultured on medium containing elevated levels of sucrose and dehydrated prior to rapid freezing in liquid nitrogen. The maximum survival of embryogenic tissue ranged from 4% to 38%, depending on the genotype. With the incorporation of a slow-cooling step, survival was generally much higher than that obtained after rapid freezing alone. Five of eight genotypes tested with this protocol gave survival percentages in excess of 55%, and a further two in excess of 33%, all after evaporative dehydration. The most effective sucrose treatment(s), however, varied with the genotype. Received: 7 October 1996 / Revision received: 16 December 1996 / Accepted 27 January 1997     

Antigenic independence of the two types of alkaline phosphatases from Serratia marcescens strain 211

The antigenic structures of phosphatases F and W appeared different: antibody anti-F cross-reacts immunospecifically with phosphatase F only. Catalytic site and antigenic site of phosphatase F seem differently located on the enzyme molecule.     

High temperature induced antibiotic sensitivity changes in Pseudomonas aeruginosa.

Pseudomonas aeruginosa, which was resistant to a wide variety of antibiotics, became sensitive to several of these antibiotics when grown and tested at 46 degrees C. Cell wall antibiotics such as penicillin G and ampicillin were only effective when added to cells growing at 46 degrees C prior to a temperature shift to 37 degrees C. Antibiotics which penetrate the cytoplasmic membrane to express their inhibiting action present a pattern different from those which are active against the outer cell wall. In order that these compounds be effective, the permeability of the cytoplasmic membrane must be further altered with agents such as EDTA which allow the penetration of actinomycin D. Inhibitors of protein synthesis, such as streptomycin and chloramphenicol, have increased access to their sites of action in cells grown at 46 degrees C. Cells grown at 46 degrees C have 40% less lipopolysaccharide (LPS) than cells grown at 37 degrees C and the LPS aggregates were of large molecular size in cells grown at 46 degrees C. Growth at 46 degrees C affects the permeability properties of the outer cell wall more than the permeability properties of the cytoplasmic membrane and this was due, in part, to the selective release of LPS of LPS-protein complexes at elevated growth temperatures.     

Characterization of the substrate specificity of alpha1,3galactosyltransferase utilizing modified N-acetyllactosamine disaccharides.

alpha1,3galactosyltransferase (alpha1,3GalT) catalyzes the synthesis of a range of glycoconjugates containing the Galalpha1,3Gal epitope which is recognized by the naturally occurring human antibody, anti-Gal. This enzyme may be a useful synthetic tool to produce a range of compounds to further investigate the binding site of anti-Gal and other proteins with a Galalpha1,3Gal binding site. Thus, the enzyme has been probed with a series of type 2 disaccharide-C8(Galbeta1-4GlcNAc-C8) analogs. The enzyme tolerated acceptors with modifications at C2 and C3 of the N-acetylglucosamine residue, producing a family of compounds with a nonreducing alpha1,3 linked galactose. Compounds that did not serve as acceptors were evaluated as inhibitors. Interestingly, the type 1 disaccharide-C8, Galbeta1-3GlcNAc-C8, was a good inhibitor of the enzyme (Ki = 270 microM vs. Km = 190 microM for Galbeta1-4GlcNAc-C8). A potential photoprobe, based on a modified type 2 disaccharide (octyl 3-amino-3-deoxy-3-N-(2-diazo-3, 3, 3-trifluoropropionyl-beta-D-galactopyranosyl-(1, 4)-2-acetamindo-2-deoxy-beta-D-glycopyranoside, (DTFP-LacNAc-C8)), was evaluated as an inhibitor of alpha1,3GalT. alpha1,3GalT bound DTFP-LacNAc-C8 with an affinity (Ki = 300 microM) similar to that displayed by the enzyme for LacNAc-C8. Additional studies were done to determine the enzyme's ability to transfer a range of sugars from UDP-sugar donors. The results of these experiments demonstrated that alpha1,3GalT has a strict specificity for UDP-Gal. Finally, inactivation studies with various amino acid modifiers were done to obtain information on the importance of different types of amino acids for alpha1,3GalT activity.     

XRD studies of UV-irradiated chitin based polyurethane elastomers

Chitin based polyurethane (PU) elastomers constituted on 4,4´-diphenylmethane diisocyanate (MDI), poly(ε-caprolactone) (PCL) and extended with blends of chitin/1,4-butane diol were synthesized via two step polymerization technique. The synthesized samples were irradiated for 50, 100 and 200 h in an UV exposure chamber as such the spectral distribution of the light is good match for terrestrial solar radiation. The crystalline behavior of the irradiated PU samples were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC) and dynamic mechanical thermal analysis (DMTA) techniques. The effect of irradiation time and chitin contents on crystallinity were studied and investigated. The maximum decrease in the crystalline behavior of samples after irradiation observed by XRD, DSC and tan δ peaks were found for the PU samples extended with lower contents of chitin (chitin/BDO; 0/100). In comparison with irradiation times the 200 h irradiation showed maximum change in the crystalline behavior.     

Removal and recovery of Cu(II) and Zn(II) using immobilized Mentha arvensis distillation waste biomass

The potential use of the immobilized Mentha arvensis distillation waste (IMADW) biomass for removal and recovery of Cu(II) and Zn(II) from aqueous was evaluated in the present study. Biosorption capacity of Cu(II) and Zn(II) on IMADW increased with increase in pH reaching a maximum at 5 for Cu(II) and 6 for Zn(II). The equilibrium sorption data agreed well with Langmuir isotherm model and pseudo-second-order kinetic model in batch mode. Cu(II) and Zn(II) uptake by IMADW was best described by pseudo-first-order kinetic model in continuous mode. Maximum Cu(II) and Zn(II) uptake by IMADW was 104.48 and 107.75 mg/g, respectively. Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were also carried out to investigate functional groups and surface changes of biomass. The results showed that IMADW biomass is a potential biomaterial to remove Cu(II) and Zn(II) ions with a high biosorption capacity from aqueous solutions.     

A SNP haplotype associated with a gene resistant to Xanthomonas axonopodis pv. malvacearum in upland cotton (Gossypium hirsutum L.)

An F_4:5 population of 285 families with each tracing back to a different F₂ plant, derived from a cotton bacterial blight resistant line ‘DeltaOpal’ and a susceptible line ‘DP388’, was artificially inoculated with bacterial blight race 18 (Xanthomonas axonopodis pv. malvacearum) to assay their resistance or susceptibility to the disease. The segregation in the F_4:5 population indicates that the resistance was conditioned by a single dominant gene designated B _12. Simple sequence repeat (SSR) markers identified as putatively linked to the resistance gene by bulked segregant analysis were confirmed on the entire F_4:5 population. Three SSR markers, CIR246, BNL3545 and BNL3644 on chromosome 14, were found closely linked to B ₁₂ . The association between CIR246 and B ₁₂ was validated among 354 plants of 16 diverse varieties. Based on Monsanto SSR/single nucleotide polymorphism (SNP) consensus map, SNP markers closely linked to CIR246 were used to screen ‘DeltaOpal’ and ‘DP388’ for polymorphism. The polymorphic SNP markers were run on the F_4:5 population and the four SNP markers spanning 3.4 cM were found to flank the resistance gene on chromosome 14. The linkage between B ₁₂ and the 4-SNP marker haplotype was validated using 18 elite cotton lines. This 4-SNP marker haplotype can be used for marker assisted selection for bacterial blight resistance breeding programs or for screening germplasm collections for this locus rapidly.