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Dive into the research topics where Juan J. Jiménez is active.

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Featured researches published by Juan J. Jiménez.


Applied Soil Ecology | 2001

Spatial distribution of earthworms in acid-soil savannas of the eastern plains of Colombia

Juan J. Jiménez; Jean-Pierre Rossi; Patrick Lavelle

The horizontal spatial distribution of earthworms in a native savanna and in a 17 year introduced pasture from the area of Carimagua (Colombia) was assessed by means of aggregation indices and geostatistical analysis. Morisita’s index (Id) and Taylor’s index (b) were calculated from field data obtained through 1 m 2 quadrats during a sampling period of 17 months and both semivariograms and contour maps were obtained at three different dates through a rapid sampling of 64, 40 cm × 40 cm × 15 cm soil blocks, regularly distributed in the nodes of a 8 × 8 grid (i.e. 70 m × 70 m). Earthworms tended to exhibit contagious distribution in both land use systems and a multivariate relationship appeared between the size of the earthworm and aggregation indices employed. Land use had no significant effect on the spatial distribution of earthworms. Earthworms belonging to different ecological categories and from diverse sizes were spatially distributed in patches of several tens of meters. Semivariograms reflected, occasionally, the size of these patches, although, no spatial structure was perceived at some dates. This might be due to the intersample distance employed (10 m) so that changing the scale of observation could reflect unseen patterns. In this study our purpose was first to determine the strength of spatial aggregation in some Neotropical earthworm species and then to observe the movement of population patches at the scale of the studied area. The use of these types of spatial analyses in conjunction may be very useful to establish the dynamics of earthworm populations in the field.


Biology and Fertility of Soils | 1998

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

Juan J. Jiménez; Ana García Moreno; Thibaud Decaëns; Patrick Lavelle; Myles Fisher; Richard J. Thomas

Abstract The structure and seasonal changes of earthworm communities were evaluated in a natural savanna and in a improved grass-legume pasture in a Colombian oxisol over a period of 18 months. One plot of 90×90 m was isolated in each of the systems and each month five samples of 1 m2×0.5 m and ten of 20×20×20 cm were randomly selected from a stratified block design. Species richness was similar in the two evaluated plots (seven species), whereas diversity measured by the index, H (Shannon and Weaver 1949) was clearly different, i.e. H=2.89 in natural savanna and H=1.29 in pasture. This is explained by differences in earthworm community structure. The average annual density in the savanna was 49.8, ranging from 10.8 to 135.8 individuals (ind) m–2, and biomass was 3.3 g m–2 (hand-sorting method), ranging from 0.9 to 11.5 g m–2. In the man-made pasture, density was 80.1 ind m–2 on average, ranging from 24 to 215.8 ind m–2 and biomass was more than tenfold higher, ranging from 29.2 to 110.4 g m–2. This was especially due to the presence of a large glossoscolecid anecic species, Martiodrilus carimaguensis Jiménez and Moreno, which has been greatly favoured by conversion of savanna to pasture. Endogeic species were dominant in the natural savanna whereas the anecic species accounted for 88% of total earthworm biomass in the pasture. Total earthworm density and biomass were significantly different in the two systems studied (t-test). The results indicate a clearly positive response of earthworm communities to improved pastures, a type of land use that is being increasingly adopted in moist neotropical savannas.


Acta Oecologica-international Journal of Ecology | 2003

Seed dispersion by surface casting activities of earthworms in Colombian grasslands

Thibaud Decaëns; Lucero Mariani; Nixon Betancourt; Juan J. Jiménez

The effects of Martiodrilus sp. (Oligochaeta, Glossoscolecidae) on the soil seed banks was investigated in a Colombian savanna and two intensive pastures. Germination and washing–sieving methods were used to compare seed density, diversity, species composition and germination rates in earthworm casts and the surrounding soil. Although large amounts of seeds were present in casts (163.65, 156.84 and 60.36 seeds per 100 g of dry casts in the savanna, the old and young pastures, respectively), germination rates were 3–40 times lower than in the surrounding soil, likely due to degradation during the gut transit. The number of viable seeds present in casts was 0.40, 7.46 and 1.99 seeds per 100 g of dry casts in the savanna, the old and young pastures, respectively. Species composition of viable seeds was quite different in casts compared to soil, probably because of selective seed ingestion by earthworms. Viable seeds deposited in surface casts each year represented 0.65%, 16.17% and 8.24% of the total viable seed bank of the soil, in the savanna, the old and young pastures, respectively. In the savanna and the old pasture, species composition in casts was more similar to the vegetation than species composition in the soil was. This may indicate that ingested seeds that survive gut transit have a greater chance to germinate than those of the soil seed bank, providing vegetation cover is sufficiently opened to enable germination processes. Thus, casts may be considered as a regeneration niche for plant species, and earthworm activity a factor that enhances, in some cases, the expression of the soil seed bank in the standing vegetation.


Plant and Soil | 2002

Earthworm communities under an agricultural intensification gradient in Colombia

Thibaud Decaëns; Juan J. Jiménez

This study was carried out in the Eastern Plains of Colombia and assessed the impact of agricultural intensification on the structure of earthworm communities. Earthworms were hand-sorted in a variety of agroecosystems of increasing intensity, from natural savanna to pastures and annual crops. An agricultural intensification index was used to rank systems along an intensification gradient, i.e. from native savanna to pastures and annual crops. Earthworm biomass, specific richness and Shannon index sharply decreased along the gradient. The disappearance of some species in cultivated systems was mostly attributed to the lack of recovery of populations after major perturbations like e.g. tillage. The more resistant species were those presenting high surface mobility (i.e. high colonisation capacity) or high population growth potential (i.e. high ability of population recovering after perturbation). Sensitive species disappeared after pasture establishment but richness was recovered in a period of about 3 years. In 17 year-old pastures, the community has regained its initial diversity and present very high biomass due to the presence of abundant populations of an anecic species. On the opposite side, annual crops had deep detrimental impacts that were more accentuated in the rotations (i.e. systems that were tilled twice a year) and were still present in a 2 year-old fallow.


Applied Soil Ecology | 1998

Population dynamics and adaptive strategies of Martiodrilus carimaguensis (oligochaeta, glossoscolecidae), a native species from the well-drained savannas of Colombia

Juan J. Jiménez; Ana García Moreno; Patrick Lavelle; Thibaud Decaëns

Abstract Martiodrilus carimaguensis (Oligochaeta, Glossoscolecidae) is a large, anecic native earthworm species which was found in natural and disturbed savannas in the Oxisols of the Colombian Llanos. Its population dynamics were studied in a native savanna, and in a 17 years old grazed grass-legume pasture where density and biomass were higher. Monthly cast deposition on the soil surface in the improved pasture was 38.4×103 fresh casts ha−1, eleven times more than in the native savanna. A strong relationship was found between numbers of M. carimaguensis and numbers of fresh surface casts. Different patterns of adaptation to the dry season were observed for adults and juveniles. Adults are active for eight months whereas juveniles enter diapause 3–4 months earlier. The vertical distribution pattern of the earthworm population also shows marked seasonal changes.


Soil Biology & Biochemistry | 2003

Phosphorus fractions and dynamics in surface earthworm casts under native and improved grasslands in a Colombian savanna Oxisol

Juan J. Jiménez; Alex Cepeda; Thibaud Decaëns; Astrid Oberson; Dennis Friesen

The objective of this study was to assess the effect of a native anecic species on phosphorus availability in an Oxisol characterised by a low chemical fertility. Experiments were carried out at Carimagua research station in a representative site of the isohyperthermic savannas on the Colombian Orinoco basin. One field study and two laboratory/incubation studies were performed in a natural herbaceous savanna and a Brachiaria decumbens and Pueraria phaseoloides pasture. In the laboratory, experiment pots were prepared containing soil collected from the respective field paddock’s topsoil. Total P content was higher in earthworm casts than in the surrounding soil in field samples, 50% in native savanna soil and more than 100% in pasture soil. In casts produced under laboratory conditions this increase was relatively low (10 – 20%). Under field conditions, almost without exception, all P fractions were increased in casts relative to the original soil (corresponding to the increase in total P content), being relatively greater in the labile inorganic P fractions. In addition, samples from the natural savanna showed that pH of casts was higher (5.2) than that of soil (4.6) in both field and laboratory samples. Except in the native savanna under field conditions, the phosphatase activity was reduced in casts by 16.7 to 44%. From our results we conclude that earthworms in the field incorporate P from litter or other organic sources (i.e. undecomposed plant and root material, earthworm faeces) which is not normally measured in the analysis of bulk soil. q 2003 Elsevier Science Ltd. All rights reserved.


Journal of Biotechnology | 2011

Protein expression vector and secretion signal peptide optimization to drive the production, secretion, and functional expression of the bacteriocin enterocin A in lactic acid bacteria.

Juan Borrero; Juan J. Jiménez; Loreto Gútiez; Carmen Herranz; Luis M. Cintas; Pablo E. Hernández

Replacement of the leader sequence (LS) of the bacteriocin enterocin A (LS(entA)) by the signal peptides (SP) of the protein Usp45 (SP(usp45)), and the bacteriocins enterocin P (SP(entP)), and hiracin JM79 (SP(hirJM79)) permits the production, secretion, and functional expression of EntA by different lactic acid bacteria (LAB). Chimeric genes encoding the SP(usp45), the SP(entP), and the SP(hirJM79) fused to mature EntA plus the EntA immunity genes (entA+entiA) were cloned into the expression vectors pNZ8048 and pMSP3545, under control of the inducible P(nisA) promoter, and in pMG36c, under control of the constitutive P(32) promoter. The amount, antimicrobial activity, and specific antimicrobial activity of the EntA produced by the recombinant Lactococcus lactis, Enterococcus faecium, E. faecalis, Lactobacillus sakei and Pediococcus acidilactici hosts varied depending on the signal peptide, the expression vector, and the host strain. However, the antimicrobial activity and the specific antimicrobial activity of the EntA produced by most of the LAB transformants was lower than expected from their production. The supernatants of the recombinant L. lactis NZ9000 (pNZUAI) and L. lactis NZ9000 (pNZHAI), overproducers of EntA, showed a 1.2- to 5.1-fold higher antimicrobial activity than that of the natural producer E. faecium T136 against different Listeria spp.


Applied Microbiology and Biotechnology | 2011

Use of the usp45 lactococcal secretion signal sequence to drive the secretion and functional expression of enterococcal bacteriocins in Lactococcus lactis

Juan Borrero; Juan J. Jiménez; Loreto Gútiez; Carmen Herranz; Luis M. Cintas; Pablo E. Hernández

Replacement of the signal peptide (SP) of the bacteriocins enterocin P (EntP) and hiracin JM79 (HirJM79), produced by Enterococcus faecium P13 and Enterococcus hirae DCH5, respectively, by the signal peptide of Usp45 (SPusp45), the major Sec-dependent protein secreted by Lactococcus lactis, permits the production, secretion, and functional expression of EntP and HirJM79 by L. lactis. Chimeric genes encoding the SPusp45 fused to either mature EntP (entP), with or without the immunity gene (entiP) or to mature HirJM79 (hirJM79), with or without the immunity gene (hiriJM79), were cloned into the expression vector pMG36c, carrying the P32 constitutive promoter, and into pNZ8048 under control of the inducible PnisA promoter. The production of EntP and HirJM79 by most of the L. lactis recombinant strains was 1.5- to 3.7-fold higher and up to 3.6-fold higher than by the E. faecium P13 and E. hirae DCH5 control strains, respectively. However, the specific antimicrobial activity of the recombinant EntP was 1.1- to 6.2-fold higher than that produced by E. faecium P13, while that of the HirJM79 was a 40% to an 89% of that produced by E. hirae DCH5. Chimeras of SPusp45 fused to mature EntP or HirJM79 drive the production and secretion of these bacteriocins in L. lactis in the absence of specific immunity and secretion proteins. The supernatants of the recombinant L. lactis NZ9000 strains, producers of EntP, showed a much higher antimicrobial activity against Listeria spp. than that of the recombinant L. lactis NZ9000 derivatives, producers of HirJM79.


Applied and Environmental Microbiology | 2012

Cloning, Production, and Functional Expression of the Bacteriocin Enterocin A, Produced by Enterococcus faecium T136, by the Yeasts Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Arxula adeninivorans

Juan Borrero; Gotthard Kunze; Juan J. Jiménez; Erik Böer; Loreto Gútiez; Carmen Herranz; Luis M. Cintas; Pablo E. Hernández

ABSTRACT The bacteriocin enterocin A (EntA) produced by Enterococcus faecium T136 has been successfully cloned and produced by the yeasts Pichia pastoris X-33EA, Kluyveromyces lactis GG799EA, Hansenula polymorpha KL8-1EA, and Arxula adeninivorans G1212EA. Moreover, P. pastoris X-33EA and K. lactis GG799EA produced EntA in larger amounts and with higher antimicrobial and specific antimicrobial activities than the EntA produced by E. faecium T136.


Journal of Industrial Microbiology & Biotechnology | 2013

Cloning, production, and functional expression of the bacteriocin sakacin A (SakA) and two SakA-derived chimeras in lactic acid bacteria (LAB) and the yeasts Pichia pastoris and Kluyveromyces lactis

Juan J. Jiménez; Juan Borrero; Dzung B. Diep; Loreto Gútiez; Ingolf F. Nes; Carmen Herranz; Luis M. Cintas; Pablo E. Hernández

Mature sakacin A (SakA, encoded by sapA) and its cognate immunity protein (SakI, encoded by sapiA), and two SakA-derived chimeras mimicking the N-terminal end of mature enterocin P (EntP/SakA) and mature enterocin A (EntA/SakA) together with SakI, were fused to different signal peptides (SP) and cloned into the protein expression vectors pNZ8048 and pMG36c for evaluation of their production and functional expression by different lactic acid bacteria. The amount, antimicrobial activity, and specific antimicrobial activity of SakA and its chimeras produced by Lactococcus lactis subsp. cremoris NZ9000 depended on the SP and the expression vector. Only L. lactis NZ9000 (pNUPS), producing EntP/SakA, showed higher bacteriocin production and antimicrobial activity than the natural SakA-producer Lactobacillus sakei Lb706. The lower antimicrobial activity of the SakA-producer L. lactis NZ9000 (pNUS) and that of the EntA/SakA-producer L. lactis NZ9000 (pNUAS) could be ascribed to secretion of truncated bacteriocins. On the other hand, of the Lb. sakei Lb706 cultures transformed with the pMG36c-derived vectors only Lb. sakei Lb706 (pGUS) overproducing SakA showed a higher antimicrobial activity than Lb. sakei Lb706. Finally, cloning of SakA and EntP/SakA into pPICZαA and pKLAC2 permitted the production of SakA and EntP/SakA by recombinant Pichia pastoris X-33 and Kluyveromyces lactis GG799 derivatives although their antimicrobial activity was lower than expected from their production.

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Thibaud Decaëns

Centre national de la recherche scientifique

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Luis M. Cintas

Complutense University of Madrid

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Carmen Herranz

Complutense University of Madrid

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Loreto Gútiez

Complutense University of Madrid

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Pablo E. Hernández

Complutense University of Madrid

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Juan Borrero

Complutense University of Madrid

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Francisco A. Comín

Spanish National Research Council

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Patrick Lavelle

International Center for Tropical Agriculture

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Sara Arbulu

Complutense University of Madrid

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Enrique Navarro

Spanish National Research Council

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