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Papers by Maria Jose Bonete Pérez

Microbial Cell Factories, 2006

Production Meeting: a comparative view on host physiology</p> </title> <spo nsor&g... more Production Meeting: a comparative view on host physiology</p> </title> <spo nsor> <note>The organisers would like to thank Novozymes Delta Ltd who generously supported the meeting.</note> </sponsor> <not e>Meeting

Genes, Jan 10, 2018

Small RNAs have been studied in detail in domains Bacteria and Eukarya but, in the case of the do... more Small RNAs have been studied in detail in domains Bacteria and Eukarya but, in the case of the domain Archaea, the knowledge is scarce and the physiological function of these small RNAs (sRNAs) is still uncertain. To extend the knowledge of sRNAs in the domain Archaea and their possible role in the regulation of the nitrogen assimilation metabolism in haloarchaea,has been used as a model microorganism. The bioinformatic approach has allowed for the prediction of 295 putative sRNAs genes in the genome of, 88 of which have been verified by means of RNA-Sequencing (RNA-Seq). The secondary structure of these sRNAs and their possible targets have been identified. Curiously, some of them present as possible target genes relating to nitrogen assimilation, such as glutamate dehydrogenase and the nitrogen regulatory PII protein. Analysis of RNA-Seq data has also revealed differences in the expression pattern of 16 sRNAs according to the nitrogen source. Consequently, RNomic and bioinformatic...

International Journal of Biochemistry, 1987

Saline Systems, 2010

Background The extraction of salt from seawater by means of coastal solar salterns is a very well... more Background The extraction of salt from seawater by means of coastal solar salterns is a very well-described process. Moreover, the characterization of these environments from ecological, biochemical and microbiological perspectives has become a key focus for many research groups all over the world over the last 20 years. In countries such as Spain, there are several examples of coastal solar salterns (mainly on the Mediterranean coast) and inland solar salterns, from which sodium chloride is obtained for human consumption. However, studies focused on the characterization of inland solar salterns are scarce and both the archaeal diversity and the plant communities inhabiting these environments remain poorly described. Results Two of the inland solar salterns (termed Redonda and Penalva), located in the Alto Vinalopó Valley (Alicante, Spain), were characterized regarding their geological and physico-chemical characteristics and their archaeal and botanical biodiversity. A preliminary ...

Extremophiles, 2012

A cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) was successfully isolated and characteri... more A cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) was successfully isolated and characterized from the halophilic archaeon Haloferax mediterranei. The enzyme is a monomer with a molecular mass of 77 kDa and optimum activity at 55°C, pH 7.5 and 1.5 M NaCl. The enzyme displayed many activities related to the degradation and transformation of starch. Cyclization was found to be the predominant activity, yielding a mixture of cyclodextrins, mainly a-CD, followed by hydrolysis and to a lesser extent coupling and disproportionation activities. Gene encoding H. mediterranei CGTase was cloned and heterologously overexpressed. Sequence analysis revealed an open reading frame of 2142 bp that encodes a protein of 713 amino acids. The amino acid sequence displayed high homology with those belonging to the a-amylase family. The CGTase is secreted to the extracellular medium by the Tat pathway. Upstream of the CGTase gene, four maltose ABC transporter genes have been sequenced (malE, malF, malG, malK). The expression of the CGTase gene yielded a fully active CGTase with similar kinetic behavior to the wild-type enzyme. The H. mediterranei CGTase is the first halophilic archaeal CGTase characterized, sequenced and expressed. Keywords Cyclodextrin glycosyltransferase Á Haloferax mediterranei Á Archaea Á Starch metabolism Á Extracellular halophilic protein Communicated by F. Robb.

FEMS Microbiology Letters, 1996

An NADP(H)-specific glutamate dehydrogenase of Haloferax mediterranei has been purified to appare... more An NADP(H)-specific glutamate dehydrogenase of Haloferax mediterranei has been purified to apparent homogeneity and characterised. The purified enzyme was stabilized by glycerol in absence of salt. Glutamate dehydrogenase from HJ: mediterranei is a hexameric enzyme with a native molecular mass of 320 kDa composed of monomers each with a molecular mass of 55 kDa. At pH 8.5 the enzyme has K, of 0.018, 0.34 and 4.2 mM for NADP+, 2-oxoglutarate and ammonium, respectively. Amino acid composition and sequence of the first 16 residues of the N-terminus have been determined.

Extremophiles, 2009

The haloarchaeon Haloferax mediterranei is able to assimilate nitrate or nitrite using the assimi... more The haloarchaeon Haloferax mediterranei is able to assimilate nitrate or nitrite using the assimilatory nitrate pathway. An assimilatory nitrate reductase (Nas) and an assimilatory nitrite reductase (NiR) catalyze the first and second reactions, respectively. The genes involved in this process are transcribed as two messengers, one polycistronic (nasABC; nasA encodes Nas) and one monocistronic (nasD; codes for NiR). Here we report the Hfx mediterranei growth as well as the Nas and NiR activities in presence of high nitrate, nitrite and salt concentrations, using different approaches such as physiological experiments and enzymatic activities assays. The nasA and nasD expression profiles are also analysed by real-time quantitative PCR. The results presented reveal that the assimilatory nitrate/ nitrite pathway in Hfx mediterranei takes place even if the salt concentration is higher than those usually present in the environments where this microorganism inhabits. This haloarchaeon grows in presence of 2 M nitrate or 50 mM nitrite, which are the highest nitrate and nitrite concentrations described from a prokaryotic microorganism. Therefore, it could be attractive for bioremediation applications in sewage plants where high salt, nitrate and nitrite concentrations are detected in wastewaters and brines.

In this work we report for the first time a post-translational modification of PII homologues fro... more In this work we report for the first time a post-translational modification of PII homologues from the Archaea Domain. Haloferax mediterranei is the first haloarchaea whose PII proteins have been studied, it possesses two of them (GlnK1 and GlnK2 ), both encoded adjacent to a gene for the ammonia transporter Amt. An approach based on 2DE, anti-GlnK immunoblot and peptide mass fingerprint (MALDI-TOF-MS) of the reactive spots showed that GlnK proteins in H. mediterranei are post-translationally uridylylated. A third spot with lower pI suggests the existence of a non-descript post-translational modification in this protein family.

Acta Crystallographica Section D Biological Crystallography, 2002

Biocatal Biotransform, 2001

ABSTRACT The kinetic mechanism of NADP-glutamate dehydrogenase (EC 1.4.1.4) from the Archaeon Hal... more ABSTRACT The kinetic mechanism of NADP-glutamate dehydrogenase (EC 1.4.1.4) from the Archaeon Haloferax mediterranei was studied in 3 M KC1 and in glycerol. Haloferax mediterranei is a halophilic organism requiring 20-25% NaCl for optimal growth, so its enzymes are stabilised by high salt concentrations. We have replaced the salt by 20% (v/v) glycerol in order to analyse if the kinetic properties and kinetic mechanism of the enzyme change at lower salt concentrations in order to apply the enzyme in a bioreactor. The kinetic mechanism was studied by initial velocity measurements with, product and substrate analog inhibition. Product and substrates analog inhibition experiments indicate that (a), NADP+ is a competitive inhibitor versus NADPH indicating that NADP+ and NADPH both bind to free enzyme and (b), the binding order of substrates is NADPH, α-ketoglutarate and ammonium. The results suggest that the mechanism in the amination reaction, with and without salt, is the same: sequential ordered with A (NADPH) binding in steady state and B (a-ketoglutarate) in rapid equilibrium, with a dead-end (abortive) complex EC, and the last substrate bound is ammonium (C).

Extremophiles, Apr 26, 2009

Three different amylolytic activities, designated AMY1, AMY2, and AMY3 were detected in the cytop... more Three different amylolytic activities, designated AMY1, AMY2, and AMY3 were detected in the cytoplasm of the extreme halophilic archaeon Haloferax mediterranei grown in a starch containing medium. This organism had also been reported to excrete an a-amylase into the external medium in such conditions. The presence of these different enzymes which are also able to degrade starch may be related to the use of the available carbohydrates and maltodextrins, including the products obtained by the action of the extracellular amylase on starch that may be transported to the cytoplasm of the organism. The behavior of these intracellular hydrolytic enzymes on starch is reported here and compared with their extracellular counterpart. Two of these glycosidic activities (AMY1, AMY3) have also been purified and further characterized. As with other halophilic enzymes, they were salt dependent and displayed maximal activity at 3 M NaCl, and 50°C. The purification steps and molecular masses have also been reported. The other activity (AMY2) was also detected in extracts from cells grown in media with glycerol instead of starch and in a yeast extract medium. This enzyme was able to degrade starch yielding small oligosaccharides and displayed similar halophilic behavior with salt requirement in the range 1.5-3 M NaCl. Keywords Halophilic archaea Á Haloferax mediterranei Á Amylolytic enzymes Á Isolation and biochemical characterization Communicated by F. Robb.

Saline Systems, Jul 1, 2008

Compuesto a base de membranas celulares liofilizadas. En la presente invención se describe un com... more Compuesto a base de membranas celulares liofilizadas. En la presente invención se describe un compuesto que comprende al menos una membrana celular liofilizada extraída de microorganismos halófilos, con al menos un 0.1% en peso seco de pigmentos carotenoides en membrana, su proceso de obtención y sus aplicaciones.