Kinetic study of Lactococcus lactis strains (SLT6 and SLT10) growth on papain-hydrolysed whey

The effect of controlled whey hydrolysis by papain on growth of two lactic acid bacteria isolated from artisanal Leben: Lactococcus lactis var. diacetylactis (SLT6 and SLT10) was investigated. The higher biomass and maximum specific growth rate (μ _max) were obtained after 30 min of hydrolysis. HPLC analysis of peptides showed that whey hydrolysis reduced the amount of peptides of MW > 400 Da and increased those peptides of MW < 400 Da. The two studied strains exhibited different peptide requirements. The pH-controlled batch cultures in 30 min hydrolysed whey followed the Monod kinetic for growth and for lactate production. The values of the key kinetic constants were: maximum specific growth rate (μ _max), 1.08 and 0.56 h^?1; yield biomass on lactose (Y _x/s), 0.20 and 0.18 g g^?1 and saturation constant K _s, 4.2 and 2.8 g L^?1 for SLT6 and SLT10, respectively. When compared with batch experimental data, the model provided good predictions for growth, lactose utilisation and lactate production profiles.     

In vivo and in vitro assessment of brain bioenergetics in aging rats

Brain energy disorders can be present in aged men and animals. To this respect, the mitochondrial and free radical theory of aging postulates that age‐associated brain energy disorders are caused by an imbalance between pro‐ and anti‐oxidants that can result in oxidative stress. Our study was designed to investigate brain energy metabolism and the activity of endogenous antioxidants during their lifespan in male Wistar rats. In vivo brain bioenergetics were measured using ³¹P nuclear magnetic resonance (NMR) spectroscopy and in vitro by polarographic analysis of mitochondrial oxidative phosphorylation. When compared to the young controls, a significant decrease of age‐dependent mitochondrial respiration and adenosine‐3‐phosphate (ATP) production measured in vitro correlated with significant reduction of forward creatine kinase reaction (kfor) and with an increase in phosphocreatine (PCr)/ATP, PCr/Pi and PME/ATP ratio measured in vivo. The levels of enzymatic antioxidants catalase, GPx and GST significantly decreased in the brain tissue as well as in the peripheral blood of aged rats. We suppose that mitochondrial dysfunction and oxidative inactivation of endogenous enzymes may participate in age‐related disorders of brain energy metabolism.     

Sampling methods for NMR-based metabolomics of Staphylococcus aureus

To select an appropriate sampling method for comparison of metabolite profiles between planktonic and biofilm Staphylococcus aureus using NMR techniques, we evaluated three methods: quenching-centrifugation (QC), filtration-quenching (FQ) and filtration-quenching-lyophilization (FQL). We found differences in metabolite loss, yield, reproducibility and metabolite profile. QC caused severe metabolite leakage and possible decomposition of nucleotides. FQ achieved high yields and reproducibility, although it had the disadvantages of long filtration and rinse times before quenching. FQL resulted in a loss of a few metabolites and a lower yield due to lyophilization. Although the biomarkers discovered by each method were nearly the same and seemed insensitive to technical variances, we conclude that FQ is the most appropriate sampling method because of its high yield and reproducibility.     

(Not) Keeping the stem straight: a proteomic analysis of maritime pine seedlings undergoing phototropism and gravitropism

Background  

Plants are subjected to continuous stimuli from the environment and have evolved an ability to respond through various growth and development processes. Phototropism and gravitropism responses enable the plant to reorient with regard to light and gravity.     

“Everything You Always Wanted to Know about Sex (but Were Afraid to Ask)” in Leishmania after Two Decades of Laboratory and Field Analyses

Leishmaniases remain a major public health problem today (350 million people at risk, 12 million infected, and 2 million new infections per year). Despite the considerable progress in cellular and molecular biology and in evolutionary genetics since 1990, the debate on the population structure and reproductive mode of Leishmania is far from being settled and therefore deserves further investigation. Two major hypotheses coexist: clonality versus sexuality. However, because of the lack of clear evidence (experimental or biological confirmation) of sexuality in Leishmania parasites, until today it has been suggested and even accepted that Leishmania species were mainly clonal with infrequent genetic recombination (see [1] for review). Two recent publications, one on Leishmania major (an in vitro experimental study) and one on Leishmania braziliensis (a population genetics analysis), once again have challenged the hypothesis of clonal reproduction. Indeed, the first study experimentally evidenced genetic recombination and proposed that Leishmania parasites are capable of having a sexual cycle consistent with meiotic processes inside the insect vector. The second investigation, based on population genetics studies, showed strong homozygosities, an observation that is incompatible with a predominantly clonal mode of reproduction at an ecological time scale (∼20–500 generations). These studies highlight the need to advance the knowledge of Leishmania biology. In this paper, we first review the reasons stimulating the continued debate and then detail the next essential steps to be taken to clarify the Leishmania reproduction model. Finally, we widen the discussion to other Trypanosomatidae and show that the progress in Leishmania biology can improve our knowledge of the evolutionary genetics of American and African trypanosomes.     

Genetic Diversity of <Emphasis Type="Italic">Acacia seyal</Emphasis> Del. Rhizobial Populations Indigenous to Senegalese Soils in Relation to Salinity and pH of the Sampling Sites

The occurrence and the distribution of rhizobial populations naturally associated to Acacia seyal Del. were characterized in 42 soils from Senegal. The diversity of rhizobial genotypes, as characterized by polymerase chain reaction restriction fragment length polymorphism (RFLP) analysis of 16S–23S rDNA, performed on DNA extracted from 138 nodules resulted in 15 clusters. Results indicated the widespread occurrence of compatible rhizobia associated to A. seyal in various ecogeographic areas. However, the clustering of rhizobial populations based on intergenic spacer (IGS) RFLP profiles did not reflect their geographic origin. Four genera were discriminated on the basis of 16S rRNA gene sequences of the strains representative for the IGS-RFLP profiles. The majority of rhizobia associated to A. seyal were affiliated to Mesorhizobium and Sinorhizobium 64 and 29%, respectively, of the different IGS-RFLP profiles. Our results demonstrate the coexistence inside the nodule of plant-pathogenic non-N₂-fixing Agrobacterium and Burkholderia strains, which induced the formation of ineffective nodules, with symbiotic rhizobia. Nodulation was recorded in saline soils and/or at low pH values or in alkaline soils, suggesting adaptability of natural rhizobial populations to major ecological environmental stress and their ability to establish symbiotic associations within these soil environments. These results contribute to the progressing research efforts to uncover the biodiversity of rhizobia and to improve nitrogen fixation in agroforestry systems in sub-Saharan Africa.     

Site-directed mutagenesis of sugar-binding lectin fragments of legume plants with the help of inverse-PCR

Method of site-directed mutagenesis that gave an opportunity to the site-independent manipulation with enough extended exposed mutagenesis fragments of gene cloning in plasmid vector was developed. With the help of this method hybrid constructions representing peas Pisum sativum (PSL) lectine with carbohydrate-binding fragment changing on that lectines from another legume plants were created. This method is suitable for obtaining the expression constructions in plasmid vectors, when is necessary to put a coding part under the control of promoter in a certain reading frame.     

Changes of phenolic metabolism and oxidative status in nitrogen-deficient Matricaria chamomilla plants

The effects of nitrogen deficiency on selected physiological attributes, phenylalanine ammonia-lyase (PAL, EC. 4.3.1.5) activity, phenolic contents, peroxidase (EC. 1.11.1.7) and catalase (EC. 1.11.1.6) activities, lipid peroxidation status and H₂O₂ accumulation were studied in N-deficient Matricaria chamomilla (L.) over 12 days. N deficiency enhanced root growth and inhibited shoot growth. Chlorophyll composition and F _v/F _m were not affected by N stress, but nitrogen and soluble proteins decreased in both the rosettes and the roots. PAL activity, expressed per mg protein, was enhanced in N-deficient rosettes and tended to decrease by the end of the experiment, while in the roots PAL activity was maintained. Total phenolic contents increased in both rosettes and roots. Peroxidase and catalase activities in N-deficient rosettes tended to decrease by the end of the experiment, while in the roots they increased on the 12th day of deficiency. Furthermore, lipid peroxidation status increased in N-deficient roots on the 12th day, indicating that antioxidative protection was insufficient to scavenge reactive oxygen species being generated. Surprisingly, H₂O₂ content was even lower in N-deficient roots by the end of the experiment, while in the leaves increased. This observation in correlation to lipid peroxidation and H₂O₂ degradation is discussed. The importance of PAL activity and phenolic metabolites in combination with antioxidative enzymes for plant protection against oxidative stress and the significance of PAL activity for the mobilization of N availability in N-deficient tissue are also discussed in view of existing information.     

Homozygous mutations in fibroblast growth factor 3 are associated with a new form of syndromic deafness characterized by inner ear agenesis, microtia, and microdontia

We identified nine individuals from three unrelated Turkish families with a unique autosomal recessive syndrome characterized by type I microtia, microdontia, and profound congenital deafness associated with a complete absence of inner ear structures (Michel aplasia). We later demonstrated three different homozygous mutations (p.S156P, p.R104X, and p.V206SfsX117) in the fibroblast growth factor 3 (FGF3) gene in affected members of these families, cosegregating with the autosomal recessive transmission as a completely penetrant phenotype. These findings demonstrate the involvement of FGF3 mutations in a human malformation syndrome for the first time and contribute to our understanding of the role this gene plays in embryonic development. Of particular interest is that the development of the inner ear is completely disturbed at a very early stage--or the otic vesicle is not induced at all--in all of the affected individuals who carried two mutant FGF3 alleles.     

Morphology, and muscle- and papilla-volume ratios, of the tongue of Laudakia stellio (Agamidae, Squamata): a histological and stereological study

We examined the histological structure of the tongue of Laudakia stellio, the starred agama lizard (Agamidae, Squamata), under light microscopy. We also investigated the muscle and papilla volume ratios, with volumes of each aspect of interest estimated according to the Cavalieri method. The macroscopically short, thick and muscle-rich front tip of the tongue of L. stellio does not show any bifurcation, and under light microscopy, the oval-shaped papilla-free front tip was seen to be covered by keratinized stratified epithelium. The dorsal and ventral parts were different, with the former partially covered by keratinized stratified epithelium and rich in secretory glands and secretory cells. The ventral part, which contained keratinized stratified cells, had a flat surface with no papillae. The dorsal surface of the anterior and posterior parts contained fungiform papillae, with the apical parts of these papillae containing minimal keratin; the interpapillar space was covered by keratin-free squamous stratified epithelium. The middle section of the tongue contained cylindrical-type papillae, with serous and mucous secretory glands and ducts at their base. Finally, the frontal and middle parts of the ventral and dorsal surfaces did not contain any taste buds, although there were some in the hind part of the dorsal surface. As morphometric estimates of volumes of the muscles and papillae, the mean volume ratios (relative to total tongue volume)+/-standard deviation were 0.66+/-0.03 and 0.33+/-0.03, with mean coefficients of error of 0.02 and 0.03, respectively.