Hans Salinas | Universidad de Concepción (original) (raw)

Papers by Hans Salinas

Fungal Genetics and Biology, 2002

N-acetyl-β-D-hexosaminidase was purified from wheat bran and characterized. The purified enzyme s... more N-acetyl-β-D-hexosaminidase was purified from wheat bran and characterized. The purified enzyme showed two protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with molecular mass of 75 and 78 kDa. The enzyme exhibited optimum pH and temperature at 5.0 and 50 o C, respectively. The enzyme was active on the substrates of p-nitrophenyl-Nacetyl-β-D-glucosaminide (pNP-GlcNAc) and p-nitrophenyl-Nacetyl-β-D-galactosaminide (pNP-GalNAc), whereas inactive on pNP-β-D-glucopyranoside, pNP-β-D-galactopyranoside, swollen chitin, and colloidal chitin, suggesting high substrate specificity. The enzyme activity for pNP-GlcNAc was stable at pH 3-6 and under 50 o C. The K m , V max and K cat for pNP-GlcNAc were 0.014 mM, 0.05 µmol/min, and 3.01×10 6 min −1 , respectively. The enzyme could be completely inhibited at 1-10 mM HgCl 2 and AgNO 3, suggesting that the intact thiol group is essential for activity. β-N-Acetylhexosaminidase from wheat bran could inhibit the conidial germination and digest the hyphae of Fusarium solani.

Fungal Genetics and Biology, 2009

Chitosan has been reported to inhibit spore germination and mycelial growth in plant pathogens, b... more Chitosan has been reported to inhibit spore germination and mycelial growth in plant pathogens, but its mode of antifungal action is poorly understood. Following chitosan treatment, we characterized plasma membrane permeabilization, and cell death and lysis in the experimental model, Neurospora crassa. Rhodamine-labeled chitosan was used to show that chitosan is internalized by fungal cells. Cell viability stains and the calcium reporter, aequorin, were used to monitor plasma membrane permeabilization and cell death. Chitosan permeabilization of the fungal plasma membrane and its uptake into fungal cells was found to be energy dependent but not to involve endocytosis. Different cell types (conidia, germ tubes and vegetative hyphae) exhibited differential sensitivity to chitosan with ungerminated conidia being the most sensitive.

Archives of Clinical Neuropsychology, 2009

The present study reports the frequent isolation of the two date palm pathogens Thielaviopsis par... more The present study reports the frequent isolation of the two date palm pathogens Thielaviopsis paradoxa (de Seynes) Hohn and T. punctulata (Hennebert) Paulin, Harrington et McNew from soil of date palm plantations at Elx, south-east Spain, using dilution plate, direct soil plating or by soil treatment either with acetic acid or phenol. The two species showed a high isolation rate.

Alle diese Gipfelausbrfiche stellen eigentlich nur HShepunkte der Dauer-tStigkeit dar. Dementspre... more Alle diese Gipfelausbrfiche stellen eigentlich nur HShepunkte der Dauer-tStigkeit dar. Dementsprechend stellt sich nach itmen am Vulkan kein Er-schSpfungszustand ein, wie dies bei paroxismalen Ausbrfichen der Fall ist, sondern nur eine kurz befristete, starke Abnahme der Dauert~itigkeit, werm abgerutschtes Material vodibergehend den Schlot verstopft, um bald darauf wieder explosiv ausgeworfen zu werden, worauf die fluktuierende Dauer-tStigkeit wieder ihren normalen Verlauf rfimmt.

Секретариат на политическите групи/Secretaría de los Grupos políticos/Sekretariát politických sku... more Секретариат на политическите групи/Secretaría de los Grupos políticos/Sekretariát politických skupin/Gruppernes sekretariat/ Sekretariat der Fraktionen/Fraktsioonide sekretariaat/Γραμματεία των Πολιτικών Ομάδων/Secretariats of political groups/Secrétariat des groupes politiques/Segreteria gruppi politici/Politisko grupu sekretariāts/Frakcijų sekretoriai/Képviselőcsoportok titkársága/Segretarjat gruppi politiċi/Fractiesecretariaten/Sekretariat Grup Politycznych/Secr. dos grupos políticos/Secretariate grupuri politice/Sekretariát politických skupín/Sekretariat političnih skupin/Poliittisten ryhmien sihteeristöt/Gruppernas sekretariat PPE-DE PSE ALDE Verts/ALE GUE/NGL IND/DEM UEN NI Strange, Soutullo Sánchez, Schneider Steenhaut, Bataille Krings Lorenzen Kyryazis, Miguel Izdebski Ciuffreda

Soil Biology & Biochemistry, 2005

This study provides evidence that egg-parasitic nematophagous fungi, Pochonia chlamydosporia, Poc... more This study provides evidence that egg-parasitic nematophagous fungi, Pochonia chlamydosporia, Pochonia rubescens and Lecanicillium lecanii, can also reduce root colonisation and root damage by a fungal pathogen. Interactions of nematophagous fungi with the take-all fungus, Gaeumannomyces graminis var. tritici (Ggt), and their influence on severity of the root disease it causes were studied in laboratory and pot experiments. In Petri dish experiments the three nematophagous fungi reduced colonisation of barley roots by Ggt and also reduced necrotic symptoms. On the contrary, root colonisation by nematophagous fungi was unaffected by Ggt. In growth tube experiments, the three nematophagous fungi again reduced Ggt root colonisation and increased effective root length of barley seedlings. This was true for both simultaneous and sequential inoculation of nematophagous fungi versus Ggt. In the pot experiments the inoculum of the tested fungi in soil was applied in the same pot, as a mixture or in layers, or in coupled pots used for wheat grown with a split-root system. The nematophagous fungi P. chlamydosporia (isolate 4624) and L. lecanii (isolate 4629), mixed with Ggt or in split root systems with the pathogen, promoted growth of wheat (i.e. increased shoot weight), although no disease reduction was found. In split root systems, lower levels of peroxidase activity were found in seedlings inoculated with Ggt in combination with the nematophagous isolates 4624 and 4629 than when the take-all fungus was applied alone.Our results show that nematophagous fungi reduce root colonisation by Ggt, root damage and stress induced senescence in Ggt-inoculated plants.

Molecular Microbiology, 2010

The antifungal mode of action of chitosan has been studied for the last 30 years, but is still li... more The antifungal mode of action of chitosan has been studied for the last 30 years, but is still little understood. We have found that the plasma membrane forms a barrier to chitosan in chitosan-resistant but not chitosan-sensitive fungi. The plasma membranes of chitosan-sensitive fungi were shown to have more polyunsaturated fatty acids than chitosan-resistant fungi, suggesting that their permeabilization by chitosan may be dependent on membrane fluidity. A fatty acid desaturase mutant of Neurospora crassa with reduced plasma membrane fluidity exhibited increased resistance to chitosan. Steady-state fluorescence anisotropy measurements on artificial membranes showed that chitosan binds to negatively charged phospholipids that alter plasma membrane fluidity and induces membrane permeabilization, which was greatest in membranes containing more polyunsaturated lipids. Phylogenetic analysis of fungi with known sensitivity to chitosan suggests that chitosan resistance may have evolved in nematophagous and entomopathogenic fungi, which naturally encounter chitosan during infection of arthropods and nematodes. Our findings provide a method to predict the sensitivity of a fungus to chitosan based on its plasma membrane composition, and suggests a new strategy for antifungal therapy, which involves treatments that increase plasma membrane fluidity to make fungi more sensitive to fungicides such as chitosan.

Nematophagous fungi constitute a group of fungal antagonists to nematodes. The latter arc small r... more Nematophagous fungi constitute a group of fungal antagonists to nematodes. The latter arc small roundworms living in soil and water. Most nematodes are saprotrophic, but many species are parasites of plants and animals (Poinar 1983). The nematophagous fungi have been suggested as promising candidatesfor bioiogical control of parasitic nematodes (Stirling 1991), but so far no successful commercial products have been .presented.

Earth and Planetary Science Letters, 1994

... Nd and Rb-Sr isotopes M. Tistl a, KP Burgath b, A. H hndorf b, H. Kreuzer b, R. Mu oz `, R. S... more ... Nd and Rb-Sr isotopes M. Tistl a, KP Burgath b, A. H hndorf b, H. Kreuzer b, R. Mu oz `, R. Salinas a Niedstrasse ... compositions of the Viravira basalts and of geochemically comparable hornblende-plagioclase dykes in the zoned complex are close to the parental melt from which ...

Cardiovascular Research, 2010

Micron, 2006

Light and scanning electron microscopy together with fungal isolation techniques were used to det... more Light and scanning electron microscopy together with fungal isolation techniques were used to detect entomopathogenic fungi within young and adult date palm (Phoenix dactylifera) petioles and to assess fungal survival in leaf tissues. The entomopathogenic fungi Beauveria bassiana, Lecanicillium dimorphum and Lecanicillium c.f. psalliotae survived inside leaf tissues at least 30 days after inoculation. Entomopathogenic fungi colonized inoculated petioles endophytically and were recovered up to 3 cm from the inoculation site. Fungi were detected inside the parenchyma and sparsely within vascular tissue using microscopy techniques. Our results show that the entomopathogenic fungi used in this study survived and colonized date palm tissues in bioassays both under laboratory and field experimental conditions with no evidence of significant damage. #

Applied Microbiology and Biotechnology, 2010

Antifungal activity of chitosan on plant pathogenic fungi has been widely studied, but little is ... more Antifungal activity of chitosan on plant pathogenic fungi has been widely studied, but little is known about the effect of chitosan on fungal biocontrol agents. In this work, we characterize the increase of conidiation induced by chitosan in fungal pathogens of invertebrates (FPI). Chitosan increased conidiation of FPI, including Beauveria bassiana, widely used as mycoinsecticide, and did not affect conidia viability or pathogenicity. Increased conidiation induced by chitosan is shown to be concentration dependent and is not associated to growth inhibition as observed for the mycoparasitic fungus Trichoderma harzianum. Real-time reverse transcription polymerase chain reaction was used to study transcript levels of two genes involved in conidiation in B. bassiana, the regulatory G protein signaling gene Bbrgs1 and the hydrophobin gene hyd1, at different chitosan concentrations. Higher levels of Bbrgs1 and hyd1 transcripts were detected on chitosan-amended media. No correlation with chitosan concentration was observed for expression of Bbrgs1 unlike hyd1. Bbrgs1 deletion mutant ∆Bbrgs1 showed that chitosan-induced conidiation is independent of Bbrgs1, suggesting an alternative mechanism controlling conidiation in B. bassiana. Our data supports that sporulation increases by chitosan, with spores retaining their viability and pathogenicity, which makes chitosan a suitable compound to increase conidia production in fungi with applications in fungal biotechnology.

Mycological Research, 2002

The present investigation deals with the main factors involved in early infection of nematode egg... more The present investigation deals with the main factors involved in early infection of nematode eggs by fungal parasites. We studied the effect of hydrophobicity on appressorium formation by germlings of Pochonia rubescens (syn. Verticillium suchlasporium), P. chlamydosporia (syn. V. chlamydosporium) and Lecanicillium lecanii (syn. V. lecanii). Appressoria were frequently formed on hydrophobic surfaces such as polyvinyl chloride or polystyrene and were infrequently formed on hydrophilic materials such as glass or aluminium. Infected eggs probed with the FITC-labelled lectin Concanavalin-A showed intense labelling corresponding to appressoria formed by fungal parasites on the eggshell surface. Proteolytic activity was found in extracts from conidia and germlings of fungal parasites (especially P. chlamydosporia) in the absence of nematode eggs. Addition of the serine proteinase inhibitors phenylmetylsulphonyl fluoride (PMSF) or diisopropyl fluorophosphonate (DFP) to the extracts reduced their proteolytic activity. PMSF was the most effective inhibitor. Zymography also revealed proteolytic activity in extracts from the three fungi tested. This activity mostly corresponded to bands of Rf 's of substrate degradation similar to that of purified main protease (P32) from P. rubescens. Other bands with molecular weight higher than P32 (low Rf ) were found especially for P. chlamydosporia extracts. For L. lecanii only bands of low Rf were found. Serum anti-P32 partially inhibited proteolytic activity of extracts from conidia and germlings. Application of PMSF and DFP to the inoculum, reduced egg penetration for the three species studied. PMSF caused the highest reduction in eggs infected by L. lecanii, while DFP significantly reduced egg infection by both P. chlamydosporia and L. lecanii. Our results therefore show hydrophobicity, appresorium formation and protease production as factors involved in early parasitism of nematode eggs.