Influence of clay minerals on sorption of bacteriolytic enzymes

Myxobacteria presumably produce extracellular bacteriolytic enzymes when they are growing in soil. In order to study their ecological significance, adsorption experiments were performed with lytic enzymes produced byMyxococcus virescens in casitone media. Different soils as well as montmorillonite and kaolinite can rapidly adsorb the bacteriolytic but not the proteolytic enzymes. About 1 gm of montmorillonite per liter of cell-free culture solution is enough for the adsorption of 97% of the bacteriolytic enzymes. The adsorption per unit weight is about 100 times greater on montmorillonite than on kaolinite. About 40% of the adsorbed enzymes can be eluted with solutions of high pH or high ionic strength. The only desorbed bacteriolytic enzyme is the alanyl-∈-N-lysine endopeptidase.     

Guidelines for model adaptation: A study of the transferability of a general seagrass ecosystem Dynamic Bayesian Networks model

In general, it is not feasible to collect enough empirical data to capture the entire range of processes that define a complex system, either intrinsically or when viewing the system from a different geographical or temporal perspective. In this context, an alternative approach is to consider model transferability, which is the act of translating a model built for one environment to another less well‐known situation. Model transferability and adaptability may be extremely beneficial—approaches that aid in the reuse and adaption of models, particularly for sites with limited data, would benefit from widespread model uptake. Besides the reduced effort required to develop a model, data collection can be simplified when transferring a model to a different application context. The research presented in this paper focused on a case study to identify and implement guidelines for model adaptation. Our study adapted a general Dynamic Bayesian Networks (DBN) of a seagrass ecosystem to a new location where nodes were similar, but the conditional probability tables varied. We focused on two species of seagrass (Zostera noltei and Zostera marina) located in Arcachon Bay, France. Expert knowledge was used to complement peer‐reviewed literature to identify which components needed adjustment including parameterization and quantification of the model and desired outcomes. We adopted both linguistic labels and scenario‐based elicitation to elicit from experts the conditional probabilities used to quantify the DBN. Following the proposed guidelines, the model structure of the general DBN was retained, but the conditional probability tables were adapted for nodes that characterized the growth dynamics in Zostera spp. population located in Arcachon Bay, as well as the seasonal variation on their reproduction. Particular attention was paid to the light variable as it is a crucial driver of growth and physiology for seagrasses. Our guidelines provide a way to adapt a general DBN to specific ecosystems to maximize model reuse and minimize re‐development effort. Especially important from a transferability perspective are guidelines for ecosystems with limited data, and how simulation and prior predictive approaches can be used in these contexts.     

Staining of Some Specific Regions of Human Chromosomes,particularly the Secondary Constriction of No. 9

SEVERAL procedures have been described recently which produce specific patterns of differential staining in human chromosomes^1–9. Techniques which involve DNA denaturation and reannealing reveal deeply stained areas on centromere and secondary constriction regions which have been equated with constitutive heterochromatin⁹.     

The mode of action of thidiazuron: auxins,indoleamines, and ion channels in the regeneration of <Emphasis Type="Italic">Echinacea purpurea</Emphasis> L.

The biochemical mechanisms underlying thidiazuron (TDZ)-induced regeneration in plant cells have not been clearly elucidated. Exposure of leaf explants of Echinacea purpurea to a medium containing TDZ results in undifferentiated cell proliferation and differentiated growth as mixed shoot organogenesis and somatic embryogenesis. The current studies were undertaken to determine the potential roles of auxin, indoleamines, and ion signaling in the dedifferentiation and redifferentiation of plant cells. E. purpurea leaf explants were found to contain auxin and the related indoleamine neurotransmitters, melatonin, and serotonin. The levels of these endogenous indoleamines were increased by exposure to TDZ associated with the induction of regeneration. The auxin-transport inhibitor 2,3,5-triiodobenzoic acid and auxin action inhibitor, p-chlorophenoxyisobutyric acid decreased the TDZ-induced regeneration but increased concentrations of endogenous serotonin and melatonin. As well, inhibitors of calcium and sodium transport significantly reduced TDZ-induced morphogenesis while increasing endogenous indoleamine content. These data indicate that TDZ-induced regeneration is the manifestation of a metabolic cascade that includes an initial signaling event, accumulation, and transport of endogenous plant signals such as auxin and melatonin, a system of secondary messengers, and a concurrent stress response.     

Total chemical synthesis,assembly of human torque teno virus genome

Torque teno virus(TTV)is a nonenveloped virus containing a single-stranded,circular DNA genome of approximately 3.8kb.We completely synthesized the 3808 nucleotides of the TTV(SANBAN isolate)genome,which contains a hairpin structure and a GC-rich region.More than 100 overlapping oligonucleotides were chemically synthesized and assembled by polymerise chain assembly reaction(PCA),and the synthesis was completed with splicing by overlap extension(SOEing).This study establishes the methodological basis of the chemical synthesis of a viral genome for use as a live attenuated vaccine or gene therapy vector.     

Evolution of resident bird breeding phenology in a landscape with heterogeneous resource phenology and carryover effects

It is generally expected that, in environments with pronounced seasonal resource peaks, birds’ reproductive success will be maximised when nestlings’ peak food demand coincides with the timing of high food availability. However in certain birds that stay resident over winter, earlier breeding leads juveniles to join the winter flock earlier, which by the prior residence effect increases their success in breeding territory competition. This trade-off between reproduction and competition may explain why, in certain species, breeding phenology is earlier and asynchronous with the resource. This study extends a previous model of the evolution of breeding phenology in a single habitat type to a landscape with two habitat types: ‘early’ and ‘late’ resource phenology. The offspring’s natal habitat type has a carryover effect upon their competitive ability regardless of which habitat type they settle in to potentially breed. We find that, when the difference in resource phenology between habitats is small (weak carryover effect), breeding phenology in the late habitat evolves to occur earlier and more asynchronously than in the early habitat, to compensate for the competitive disadvantage to juveniles raised there. However if the difference is large (strong carryover effect), then the reproductive cost of earlier breeding outweighs the benefit of the compensation, so instead breeding phenology in the late habitat evolves to become more synchronous with the resource. Recruitment is generally asymmetric, from early to late habitat type. However if the early habitat is less frequent in the landscape or produces fewer offspring, then the asymmetry is reduced, and if there is some natal habitat-type fidelity, then recruitment can have an insular pattern, i.e. most recruits to each habitat type come from that same habitat type. We detail the different scenarios in which the different recruitment patterns are predicted, and we propose that they have implications for local adaptation.     

Auxin-like activity of extract from hypertrophied tissue of <Emphasis Type="Italic">Acacia eburnea</Emphasis> infected with <Emphasis Type="Italic">Ravenelia esculenta</Emphasis>

Ravenelia esculenta Naras. and Thirum. is a rust, pathogenic to Acacia eburnea Willd. The infection leads to hypertrophy changing the morphology with bizarre shapes of plant organs. Healthy and infected tissues were subjected to extraction of IAA and indole derivatives and were estimated by spectrophotometric methods. The hypertrophy produced was presumed to be due to increase in the indole-3-acetic acid (IAA) content in the infected tissue, however, the amount of IAA in infected tissues decreased with the progression of disease. Concomitantly, the infected tissue showed the presence of a novel, slow migrating, indole derivative on TLC. Cultured shoot tips of Withania somnifera were dosed with the methanolic extract of the infected hypertrophied tissue (MEHT) (0.25, 0.5, 0.75, 1.00 and 1.25 mg/l). The stimulation in shoot growth along with profuse rooting was observed in a dose dependent manner with maximum at 1.00 and 1.25 mg/l concentration.     

Spatio-temporal tumour model for analysis and mechanism of action of intracellular drug accumulation

We have developed a one-dimensional tumour simulator to describe the biodistribution of chemotherapeutic drugs to a tumoral lesion and the tumour cell’s response to therapy. A three-compartment model is used for drug dynamics within the tumour. The first compartment represents the extracellular space in which cells move, the second corresponds to the intracellular fluid space (including cell membrane) which is in direct equilibrium with the extracellular space, and the third is a non-exchangeable compartment that represents sequestered drug which is trapped in the nucleus to damage the cellular DNA, directly triggering cell death. Analytical and numerical techniques (Finite Element Method) are used to describe the tumour’s response to therapy and the effect of parameter variation on the drug concentration profiles in the three compartments.     

Diversity of halophilic microorganisms: Environments,phylogeny, physiology,and applications

The phylogenetic diversity of microorganisms living at high salt concentrations is surprising. Halophiles are found in each of the three domains: Archaea, Bacteria, and Eucarya. The metabolic diversity of halophiles is great as well: they include oxygenic and anoxygenic phototrophs, aerobic heterotrophs, fermenters, denitrifiers, sulfate reducers, and methanogens. The diversity of metabolic types encountered decreases with salinity. The upper salinity limit at which each dissimilatory process takes place is correlated with the amount of energy generated and the energetic cost of osmotic adaptation. Our understanding of the biodiversity in salt-saturated environments has increased greatly in recent years. Using a combination of culture techniques, molecular biological methods, and chemotaxonomic studies, we have obtained information on the nature of the halophilic Archaea as well as the halophilic Bacteria that inhabit saltern crystallizer ponds. Several halophilic microorganisms are being exploited in biotechnology. In some cases, such as the production of ectoine, the product is directly related to the halophilic behavior of the producing microorganism. In other cases, such as the extraction of β-carotene from Dunaliella or the potential use of Haloferax species for the production of poly-β-hydroxyalkanoate or extracellular polysaccharides, similar products can be obtained from non-halophiles, but halophilic microorganisms may present advantages over the use of non-halophilic counterparts. Journal of Industrial Microbiology & Biotechnology (2002) 28, 56–63 DOI: 10.1038/sj/jim/7000176 Received 20 May 2001/ Accepted in revised form 20 June 2001