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991.
Llamas I Suárez A Quesada E Béjar V del Moral A 《Extremophiles : life under extreme conditions》2003,7(3):205-211
Halomonas eurihalina is a moderately halophilic bacterium which produces exopolysaccharides potentially of great use in many fields of industry and ecology. Strain F2-7 of H. eurihalina synthesizes an anionic exopolysaccharide known as polymer V2-7, which not only has emulsifying activity but also becomes viscous under acidic conditions, and therefore we consider it worthwhile making a detailed study of the genetics of this strain. By insertional mutagenesis using the mini-Tn 5 Km2 transposon we isolated and characterized a mutant strain, S36 K, which requires both arginine and uracil for growth and does not excrete EPS. S36 K carries a mutation within the carB gene that encodes the synthesis of the large subunit of the carbamoylphosphate synthetase enzyme, which in turn catalyzes the synthesis of carbamoylphosphate, an important precursor of arginine and pyrimidines. We describe here the cloning and characterization of the carAB genes, which encode carbamoylphosphate synthetase in Halomonas eurihalina, and discuss this enzyme's possible role in the pathways for the synthesis of exopolysaccharides in strain F2-7. 相似文献
992.
This is the first study of caprellid amphipods from the coast of Papua New Guinea. Several collections from Madang Lagoon
(north) and Bootless Bay (south) have been studied. Seven species in seven genera are recorded, of which Pseudoproto papua sp. nov. is described as new to science. The genus Pseudoproto Mayer, 1903 has consisted, so far, of only one species, Pseudoproto fallax Mayer, 1903. Although only a single male has been found of Pseudoproto papua sp. nov., differences in antennae, mouthparts, gnathopod 2 and pereopods 3 and 4 have revealed that it represents a new species
of Pseudoproto. Lateral view figures of all species, together with a key to species level for the Caprellidea from Papua New Guinea are
also included.
Communicated by H.-D. Franke 相似文献
993.
Temporal and spatial recruitment patterns of the cyclostome bryozoan Disporella hispida were monitored using settlement plates arranged along three benthic communities of an artificial reef at Blanes (NE Spain,
NW Mediterranean). At the study site, the species mainly inhabits semi-obscure caves. By studying recruitment over one year
I first inferred the larval release period for D. hispida and described its temporal occurrence in the communities and stations studied. Secondly, I attempted to determine whether
the predicted restricted dispersal may account for the species' distribution at the study site. To this purpose, I compared
the distribution of early recruits (15 days old) with that of adults. I also investigated environmental factors which may
affect the extent of larval dispersal, and described the effects of post-recruitment processes occurring over a 4-month period.
The brooding period, inferred from the study of early recruitment, was linked to spring-increments and autumn-decrements of
water temperatures. Early recruits were distributed non-randomly in the communities and stations studied, being most abundant
in the habitats where adults live. Strong hydrodynamic events seemed to modify this pattern, allowing recruitment out of the
parental communities, and may hinder settlement. Post-recruitment mortality events were likely to prevent colonisation of
habitats where the species do not live. Overall, philopatry and low post-recruitment mortality in the parental communities
appeared to be the main mechanisms determining the distribution of D. hispida at the study site.
Electronic Publication 相似文献
994.
Escobar C Hernández LE Jiménez A Creissen G Ruiz MT Mullineaux PM 《Plant cell reports》2003,21(7):699-704
We have explored the transient over-expression of Arabidopsis thaliana ascorbate peroxidase 3 (APX3) in Nicotiana benthamiana using a viral vector based on the potato virus X (PVX). Plants infected with a PVX:APX3 hybrid had a similar progression of viral particles compared to control plants infected with a PVX:GFP hybrid, indicating that infection was not affected by the over-expression of heterologous APX3. Our results also showed that in PVX:APX3-infected plants, the hybrid virus directed a high level of APX3 expression and the recombinant protein was functional, as inferred from the higher APX activity compared to mock and PVX:GFP hybrid-infected plants. The PVX recombinant expression system used is a simple and quick method for transient expression of heterologous APXs, which are expected to suffer specific processing in plant cells. 相似文献
995.
Semedo T Santos MA Lopes MF Figueiredo Marques JJ Barreto Crespo MT Tenreiro R 《Systematic and applied microbiology》2003,26(1):13-22
The occurrence of several virulence traits (cytolysin, adhesins and hydrolytic enzymes) was investigated in a collection of 164 enterococci, including food and clinical isolates (from human and veterinary origin), as well as type and reference strains from 20 enterococcal species. Up to fifteen different cyl genotypes were found, as well as silent cyl genes. The occurrence of the cyl operon and haemolytic potential seems to be widespread in the genus. A significant association of this virulent trait with clinical isolates was found (p < 0.05). High levels of incidence were also observed for genes encoding surface adhesins (esp, efaA(fs), efaA(fm)), agg and gelE, irrespectively of species allocation and origin of strains. Although gelE behaves as silent in the majority of the strains, gelatinase activity predominates in clinical isolates, whereas lipase and DNase were mainly detected in food isolates pointing to their minor role as virulence determinants. No hyaluronidase activity was detected for all strains. Numerical hierarchic data analysis grouped the strains in three main clusters, two of them including a total of 50 strains with low number of virulence determinants (from 2 to 7) and the other with 114 strains with a high virulence potential (up to 12 determinants). No statistical association was found between virulence clusters and species allocation (p > 0.10), strongly suggesting that virulence determinants are a common trait in the genus Enterococcus. Clinical strains seem to be significantly associated with high virulence potential, whereas food, commensal and environmental strains harbour fewer virulence determinants (p < 0.01). A high level of relative diversity in virulence patterns was observed (Shannon's index varies from 0.95 to 1.0 among clusters), reinforcing the strain-specific nature of the association of virulence factors. Although a low risk seems to be associated with the use of enterococci in long-established artisanal cheeses, screening of virulence traits and their cross-synergies must be performed, particularly for commercial starters, probiotic strains and products to be used by high risk population groups. 相似文献
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1000.
Avila CM Sillero JC Rubiales D Moreno MT Torres AM 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,107(2):353-358
Bulk segregant analysis was used to identify random amplified polymorphic DNA (RAPD) markers linked to a gene determining hypersensitive resistance in Vicia faba line 2N52 against race 1 of the rust fungus Uromyces viciae-fabae. The monogenic nature of the resistance was determined by analyzing the F(2) population from a cross between resistant line 2N52 and susceptible line VF-176, and further confirmed in the F(2:3)-derived families. Linkage of the RAPD markers was confirmed by screening 55 F(2) plants segregating for resistance. Three RAPD markers (OPD13(736), OPL18(1032) and OPI20(900)) were mapped in coupling phase to the resistance gene for race 1 ( Uvf-1). No recombinants between OPI20(900) and Uvf-1 were detected. Two additional markers (OPP02(1172) and OPR07(930)) were linked to the gene in repulsion phase at a distance of 9.9 and 11.5 cM, respectively. The application of marker-assisted selection to develop new faba bean varieties with rust resistance genes is discussed. 相似文献