Occurrence of Agrobacterium tumefaciens Biovar 3 on Grapevine in Brazil

Occurrence of crown gall on grape was observed in a vineyard in Minas Gerais State, Brazil. Isolations of the pathogen yielded a bacterium which incited galls on grapevine, tomato and bryophillum. The bacterium was confirmed as Agrobacterium tumefaciens and its characterization showed it to be biovar 3. This is the first report on the occurrence of the biovar 3 of A. tumefaciens on grapevine in Brazil.     

Use of scanning electron microscopy and energy dispersive X-ray spectroscopy to identify key fouling species during alternating tangential filtration

Alternating tangential flow filtration (ATF) has become one of the primary methods for cell retention and clarification in perfusion bioreactors. However, membrane fouling can cause product sieving losses that limit the performance of these systems. This study used scanning electron microscopy and energy dispersive X-ray spectroscopy to identify the nature and location of foulants on 0.2 μm polyethersulfone hollow fiber membranes after use in industrial Chinese hamster ovary cell perfusion bioreactors for monoclonal antibody production. Membrane fouling was dominated by proteinaceous material, primarily host cell proteins along with some monoclonal antibody. Fouling occurred primarily on the lumen surface with much less protein trapped within the depth of the fiber. Protein deposition was also most pronounced near the inlet/exit of the hollow fibers, which are the regions with the greatest flux (and transmembrane pressure) during the cyclical operation of the ATF. These results provide important insights into the underlying phenomena governing the fouling behavior of ATF systems for continuous bioprocessing.     

The regulation of lactate dehydrogenase activity in soy-bean seedlings

An electrophoretically homogeneous lactate dehydrogenase was isolated from soybean seedlings, the specific activity of which was approximately 1800 times higher than the crude extract. From the dependence of the rate of reaction catalyzed by lactate dehydrogenase on substrate concentration, Michaelis constants and Hill coefficients were determined for four natural substrates,i.e. lactate, pyruvate, NAD and NADH. The enzyme from soy-bean plants is non-competitively inhibited by oxalate and mesoxalate,i.e. by the compounds analogous to the substrate. At pyruvate concentrations above 0.8 mM, the rate of reaction catalyzed by lactate dehydrogenase from soy-bean plants decreases, fructose diphosphate and ATP function as inhibitors as well. The inhibition by ATP is pH dependent, which seems to be of importance for the regulation of enzyme activityin vivo.     

Phenotypic suppression of morphogenetic mutants of Dictyostelium discoideum.

The effects of cAMP pulses on the capacity of 15 aggregateless mutants to differentiate and construct fruiting bodies are compared to those obtained when mutant cells are starved with wild-type amoebae. Mutant strains are classified into three main groups depending upon the degree to which their phenotypic defects can be corrected. These data extend studies published earlier [Darmon, M., Brachet, P., and Pereira da Silva, L. (1975). Chemotactic signals induce cell differentiation in Dictyostelium discoideum. Proc. Nat. Acad. Sci. USA72, 3163–3166; Pereira da Silva, L., Darmon, M., Brachet, P., Klein, C., and Barrand, P. (1975). Induction of cell differentiation by the chemotactic signal in Dictyostelium discoideum. In “Proceedings of the Tenth FEBS Meeting,” pp. 269–276]. (1) Only one mutant was unresponsive both to cAMP pulses and to the presence of wild-type amoebae and did not display any of the properties of differentiated cells. (2) Following treatment with cAMP pulses, 11 mutants developed certain properties of aggregation-competent amoebae. They increased their levels of cellular phosphodiesterase, showed an enhanced chemotactic sensitivity to cAMP, and established specific cell contacts. None of these amoebae could differentiate further. They did co-aggregate to some extent with wild-type cells, but failed to differentiate into spores. Rather, mutant cells were excluded from the pseudoplasmodium during the process of morphogenesis of the fruiting body. (3) In contrast, the aggregateless phenotype of three mutants was fully corrected by both cAMP pulses and the presence of wild-type cells. These findings are discussed on the basis of a relationship between the chemotactic signal and cell differentiation.     

Combined use of serological tests for the purpose of the diagnosis and study of Q-rickettsiosis

The combined use of the complement fixation test, the indirect immunofluorescent test and the ring precipitation test with C. burnetii antigen greatly enhances the effectiveness or serological study, as it allows not only to find out the spread of infection among population more completely, but also to differentiate, to a certain extent, "fresh" infectious process from immunological trace reaction. The arguments are presented in favor of introducing the antigen of C. burnetii, phase I, into practice, especially in surveying the sera of farm animals.     

Characterization of natural populations of Nitrobacter spp. using PCR/RFLP analysis of the ribosomal intergenic spacer

DNA sequences from the intergenic spacer (IGS) region of the ribosomal operon were amplified by the polymerase chain reaction (PCR) technique using two primers derived from 16S and 23S rRNA conserved sequences. The PCR products, cleaved by 4 base cutting restriction enzymes, were used to differentiate Nitrobacter strains. This method offered a convenient alternative to serological testing for characterization of Nitrobacter isolates and enabled a large number of strains to be genotypically characterized easily and rapidly. This method was successfully used to characterize natural populations of Nitrobacter from various soils and a lake. A diversity was demonstrated in various soils, and in a lake both in freshwater and in sediments. Strains closely related to both WL and LL were found in these eco-systems. It seems that the diversity of Nitrobacter populations was not associated with global environments but may be related to the presence of locally coexisting niches.Non-commun abbreviations PCR polymerase chain reaction - RFLP restriction fragment length polymorphism - IGS intergenic spacer     

Heterogeneity of mutations in the uroporphyrinogen III synthase gene in congenital erythropoietic porphyria

Summary Congenital erythropoietic porphyria (CEP) or Günther's disease is an inborn error of heme biosynthesis transmitted as an autosomal recessive trait and characterized by a profound deficiency of uroporphyrinogen III synthase (UROIIIS) activity. We have previously described two missense mutations in the UROIIIS gene, confirming that the primary defect responsible for CEP is a structural alteration of this gene. We have extended our work to 5 additional unrelated families. Two new point mutations, a deletion and an insertion have been found in the messenger RNA. Our study shows that a molecular heterogeneity of the mutations exists in Günther's disease. One mutation (C73R), however, appears to be more frequent than the others. Finally, the different normal and mutated proteins have been expressed in Escherichia coli to determine the consequence of the mutations on the enzyme activity.     

Analysis of a ribosomal RNA operon in the actinomycete Frankia.

The organisation of ribosomal RNA-encoding (rrn) genes has been studied in Frankia sp. strain ORS020606. The two rrn clusters present in Frankia strain ORS020606 were isolated from genomic banks in phage lambda EMBL3 by hybridization with oligodeoxyribonucleotide probes. The 5'-3' gene order is the usual one for bacteria: 16S-23S-5S. The two clusters are not distinguishable by restriction enzyme mapping inside the coding section, but vary considerably outside it. Sequencing showed that the 16S-rRNA-encoding gene of ORS020606 is very closely related to that of another Alnus-infective Frankia strain (Ag45/Mut15) and highly homologous to corresponding genes of Streptomyces spp. Two possible promoter sequences were detected upstream from the 16S gene, while no tRNA-encoding gene was detected in the whole operon. Regions with a high proportion of divergence for the study of phylogenetic relationships within the genus were looked for and found in the first intergenic spacer, in the 23S and in the 16S gene.     

The defense-related STH-2 gene product of potato shows race-specific accumulation after inoculation with low concentrations of Phytophthora infestans zoospores

The defense-related STH-2 gene is rapidly activated following infection or elicitor treatment of potato (Solanum tuberosum L.) tubers. However, its physiological or biochemical function is unknown. To study the STH-2 gene product and its accumulation during the defense response, we raised antibodies to a β-galactosidase-STH-2 fusion protein in Escherichia coli. The antiserum specifically recognized a protein of the predicted 17-kDa size in extracts of elicited tuber disks when analyzed by Western blot. In control extracts this band was not detected. The accumulation of STH-2 protein in response to incompatible and compatible zoospores of Phytophthora infestans (Mont.) de Bary depended on the inoculum density applied. Whereas a low concentration of spores induced accumulation of STH-2 protein faster in the incompatible than the compatible interaction, this difference in timing was less pronounced at higher inoculum densities. Inoculation with a high concentration of compatible spores also resulted in the disappearance of STH-2 protein late during the infection. In both control and induced tuber tissue the antibody strongly reacted with an unknown protein of 18 kDa. This protein was present constitutively in tubers, but in leaves its accumulation was stimulated by inoculation with P. infestans.