Mateo Rivas | Universidad Nacional Mayor de San Marcos (original) (raw)

Papers by Mateo Rivas

Molecular Plant-microbe Interactions, 2005

Bacteria belonging to the family Rhizobiaceae may establish beneficial or harmful relationships w... more Bacteria belonging to the family Rhizobiaceae may establish beneficial or harmful relationships with plants. The legume endosymbionts contain nod and nif genes responsible for nodule formation and nitrogen fixation, respectively, whereas the pathogenic strains carry vir genes responsible for the formation of tumors or hairy roots. The symbiotic and pathogenic strains currently belong to different species of the genus Rhizobium and, until now, no strains able to establish symbiosis with legumes and also to induce tumors or hairy roots in plants have been reported. Here, we report for the first time the occurrence of two rhizobial strains (163C and ATCC11325T) belonging to Rhizobium rhizogenes able to induce hairy roots or tumors in plants and also to nodulate Phaseolus vulgaris under natural environmental conditions. Symbiotic plasmids (pSym) containing nod and nif genes and pTi- or pRi-type plasmids containing vir genes were found in these strains. The nodD and nifH genes of the strains from this study are phylogenetically related to those of Sinorhizobium strains nodulating P. vulgaris. The virA and virB4 genes from strain 163C are phylogenetically related to those of R. tumefaciens C58, whereas the same genes from strain ATCC 11325T are related to those of hairy root-inducing strains. These findings may be of high relevance for the better understanding of plant-microbe interactions and knowledge of rhizobial phylogenetic history.

International Journal of Systematic and Evolutionary Microbiology, 2003

A bacterial strain (designated IH5 T ), isolated from rhizospheric soil of grasses growing sponta... more A bacterial strain (designated IH5 T ), isolated from rhizospheric soil of grasses growing spontaneously in Spanish soil, actively solubilized phosphates in vitro when bicalcium phosphate was used as a phosphorus source. This strain was Gram-negative, strictly aerobic, rod-shaped and motile. The strain produced catalase, but not oxidase. Cellulose, casein, starch, gelatin, aesculin and urea were not hydrolysed. Growth was observed with many carbohydrates as the carbon source. The main non-polar fatty acids detected were hexadecenoic acid (C 16 : 1 ), hexadecanoic acid (C 16 : 0 ) and octadecenoic acid (C 18 : 1 ). The hydroxy fatty acids detected were 3-hydroxydecanoic acid (C 10 : 0 3-OH), 3-hydroxydodecanoic acid (C 12 : 0 3-OH) and 2-hydroxydodecanoic acid (C 12 : 0 2-OH). Phylogenetic analysis of 16S rRNA indicated that this bacterium belongs to the genus Pseudomonas in the c-subclass of the Proteobacteria and that the closest related species is Pseudomonas graminis. The DNA G+C content was 61 mol%. DNA-DNA hybridization showed 23 % relatedness between strain IH5 T and P. graminis DSM 11363 T . Therefore, strain IH5 T belongs to a novel species from the genus Pseudomonas, for which the name Pseudomonas rhizosphaerae sp. nov. is proposed (type strain, IH5 T =LMG 21640 T =CECT 5726 T ).

Journal of Food Science, 1992

Total, soluble and bound peroxidase activities were studied on frozen green beans stored under pr... more Total, soluble and bound peroxidase activities were studied on frozen green beans stored under proper conditions (–18°C, -22°C, and in display freezer) and under adverse conditions (with temperature fluctuations). Blanching inactivated the enzyme; there was no regeneration for 12 mo at -22°C, but a slight regeneration at - 18°C. Sensory quality of the properly stored product was acceptable 1 yr or longer. Storage in a display freezer over 60 days did not affect peroxidase activity. Temperature fluctuations were deleterious for sensory quality and total peroxidase activity was only slightly regenerated.

British Journal of Radiology, 1992

The use of technetium-99m hexamethyl-propyleneamine oxime ( 99 Tc m -HMPAO) in the diagnosis of b... more The use of technetium-99m hexamethyl-propyleneamine oxime ( 99 Tc m -HMPAO) in the diagnosis of brain death has been evaluated in 41 studies of 37 patients with severe brain injury, who were under the effect of drugs or when other diagnostic methods were equivocal. HMPAO studies were compared with conventional radionuclide angiography performed simultaneously by intravenous administration of HMPAO as a bolus. The ages of patients ranged from 4 months to 75 years. Dynamic flow images and 5-min static uptake images were acquired following bolus injection of 555 Mbq of "Tc m -HMPAO. All patients showing no brain uptake were confirmed as brain-dead by standard clinical criteria, with no contradictory cases in the static study. In addition, all patients who were not brain-dead showed HMPAO uptake at least in the brainstem. Dynamic flow images were equivocal in five patients, four of whom had no uptake on static images and clinically confirmed brain death. In addition, two other cases showed "mismatched" dynamic and static images: in one case no perfusion was observed on flow images but uptake restricted to the posterior fossa was seen on static images; the other case showed perfusion on the dynamic study and static imaging revealed hemispheric uptake with no posterior fossa uptake. Static perfusion ^"c m -HMPAO studies offer advantages over conventional brain scintigraphy, better results being due to adequate assessment of posterior fossa activity and avoiding equivocal studies.

Chemistry-a European Journal, 1996

A strategy based on a Stille cross-coupling reaction of organostannanes interrupted at the reduct... more A strategy based on a Stille cross-coupling reaction of organostannanes interrupted at the reductive elimination step has been applied to the synthesis of oxa- and azapalladacycles with the general formula cis-[PdArR(L)2]. The synthesis of oxapalladacycles was achieved under mild conditions by reaction of 2-iodo- or 2-bromophenyloxymethylstannanes with [Pd(PPh3)4]. The synthesis of an aza analogue was similarly carried out from the corresponding 2-iodoaniline derivative. One of the substituted oxapalladacycles rearranged to release steric strain between the palladium and a chloride substituent on the aryl ring, an isomerization promoted by traces of water. In one case, the arylpalladium(II) intermediate of oxidative addition was isolated by using a palladium(0) complex with a bidentate diphosphane. A variety of new palladacycles, including complexes with weakly coordinating ligands, were prepared by ligand substitution. Reaction of the palladacycles with dimethyl acetylene-dicarboxylate led to the formation of chromenes or dihydroquinolines by insertion followed by reductive elimination.

International Journal of Systematic and Evolutionary Microbiology, 2005

Bacterial strain PETP02 T was isolated from nodules of Trifolium pratense growing in a Spanish so... more Bacterial strain PETP02 T was isolated from nodules of Trifolium pratense growing in a Spanish soil. Phylogenetic analysis of the 16S rRNA gene sequence showed that this strain represents a member of the genus Phyllobacterium. However, divergence found with the 16S rRNA gene sequence of the single recognized species of this genus, Phyllobacterium myrsinacearum, indicated that strain PETP02 T belongs to a different species. The results of DNA-DNA hybridization, phenotypic tests and fatty acid analyses confirmed that this strain represents a novel species of the genus Phyllobacterium, for which the name Phyllobacterium trifolii sp. nov. is proposed. The type strain is PETP02 T (=LMG 22712 T =CECT 7015 T ). This strain was strictly aerobic and used several carbohydrates as carbon source. It was not able to reduce nitrate. Aesculin hydrolysis was negative. It did not produce urease, arginine dihydrolase, gelatinase or b-galactosidase. The DNA G+C content was 56?4 mol%. The nodD gene of this strain showed a sequence closely related to those of strains able to nodulate Lupinus. Infectivity tests showed that this strain is able to produce nodules in both Trifolium repens and Lupinus albus.

Pmc Biophysics, 2009

FtsZ is a GTPase that assembles at midcell into a dynamic ring that constricts the membrane to in... more FtsZ is a GTPase that assembles at midcell into a dynamic ring that constricts the membrane to induce cell division in the majority of bacteria, in many archea and several organelles. In vitro, FtsZ polymerizes in a GTP-dependent manner forming a variety of filamentous flexible structures. Based on data derived from the measurement of the in vitro polymerization of Escherichia coli FtsZ cell division protein we have formulated a model in which the fine balance between curvature, flexibility and lateral interactions accounts for structural and dynamic properties of the FtsZ polymers observed with AFM. The experimental results have been used by the model to calibrate the interaction energies and the values obtained indicate that the filaments are very plastic. The extension of the model to explore filament behavior on a cylindrical surface has shown that the FtsZ condensates promoted by lateral interactions can easily form ring structures through minor modulations of either filament curvature or longitudinal bond energies. The condensation of short, monomer exchanging filaments into rings is shown to produce enough force to induce membrane deformations.

Organometallics, 1998

The oxidative addition of o-(Me 2 RSiCH 2 O)C 6 H 4 I (R = Me, Ph, F) to palladium(0) complexes [... more The oxidative addition of o-(Me 2 RSiCH 2 O)C 6 H 4 I (R = Me, Ph, F) to palladium(0) complexes [Pd(PPh 3 )], [Pd(dba)(AsPh 3 ) 2 ] (dba = dibenzylideneacetone), and [Pd(dba)(L 2 )] [L 2 = 1,1&#x27;-bis(diphenylphosphino)ferrocene (dppf), 2,2&#x27;-bipyridine (bpy), o-phenanthroline ...

Organometallics, 1997

Transmetalation of organosilanes with organopalladium(II) complexes is a key step in the syntheti... more Transmetalation of organosilanes with organopalladium(II) complexes is a key step in the synthetically useful Hiyama cross-coupling reaction (eq 1), 1 an attractive alternative to the Stille coupling reaction of organostannanes. 2 However, although organosilanes are more convenient reagents than organostannanes in organic synthesis from the point of view of their toxicity and ecological impact, silanes are considerably less reactive toward transmetalation with the in situ generated organopalladium complexes. 3,4 In practice, pal-ladium-catalyzed coupling of alkenyl or aryl halides with alkenyl-, allyl-, and alkynylsilanes (Hiyama reaction) is only possible in the presence of stoichiometric amounts of a fluoride salt as the activating agent. 5 The best results are usually obtained by using less readily available fluorosilanes as the nucleophilic partners, 1,5 although the presence of the fluoride ion (TASF or TBAF) 6 as a promoter is still necessary. Probably, the acceleration observed in the presence of fluoride is a consequence of the formation of a pentacoordinated fluorosilane intermediate, more nucleophilic toward the organopalladium in the rate-determining transmetalation step. 1,5,7,8 Fluoride salts have also been found to enhance the reactivity of alkenyl-and arylboronic acids in their cross-coupling with organic electrophiles (Suzuki reaction) by the likely formation of a reactive fluoroborate. 9,10 Alternatively, fluoride also promotes X (a) For a review on the transmetalation of allyl-, alkenyl-, alkynyl-, and arylsilanes with Pd(II) salts, see: Akhrem, I. S.; Chistovalova, N. M.; Vol'pin, M. E. Russ. Chem. Rev. 1983, 52, 542. (b) Weber, W. P.; Felix, R. A.; Willard, A. K.; Koenig, K. E. Tetrahedron Lett. 1971, 4701. (c) Yamamoto, K.; Shinohara, K.; Ohuchi, T.; Kumada, M. Tetrahedron Lett. 1974, 1153. (4) Allylsilanes are several orders of magnitude less reactive than allylstannanes toward electrophiles, see: Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938.