Characterisation of three temperate phages released from the same Lactobacillus paracasei commercial strain

Lysogeny entails more economical and technological risks in probiotic Lactobacillus casei/paracasei bacteria than in other lactic acid bacteria, due to economic value. Lysogeny is widely spread among L. casei/paracasei strains. Siphophages C_L1 and C_L2, isolated from noninfected lysed‐cultures of commercial L. paracasei A, are thermoresistant, have identical host spectrum, latent and burst times, whereas burst sizes are 148 and 85, respectively. Mitomycin C induction of L. paracasei A yielded prophage iA2, whose presence was confirmed on the strain genome and whose restriction patterns differed from phages C_L1 and C_L2. The latter shared several restriction fragments, probably indicating a common origin.     

DIGESTION OF MYOFIBRILLAR AND SARCOPLASMIC FRACTIONS FROM MENHADEN MUSCLE BY THE ACTION OF MENHADEN (Brevoortia spp.) AND WHITE CROAKER (Micropogonias furnieri) TRYPSINS

Trypsins from the pyloric caeca of menhaden (Brevoortia spp.) and croaker (Micropogonias furnieri) were used for hydrolysis of both myofibrillar and sarcoplasmic fractions from menhaden muscle. Digestion of muscle proteins was carried out at 37C for 20 min with the pH maintained at either 3, 4, 5, 6, 7, 8 or 9; or for 60 min at the pH's of 5, 7, 8 or 9 at 30C and 37C. The hydrolytic action was evaluated based on the concentration of peptides solubilized. Solubility after digestion of myofibrillar, sarcoplasmic fraction and hemoglobin was optimum at basic pH. The sarcoplasmic fraction was solubilized more than the myofibrillar fraction by both fish trypsins. Similar results were obtained with both crude pyloric extracts and purified trypsins from menhaden and white croaker. Thus, the preparation of the crude pyloric caeca may be preferentially used, because of its low cost as well as the simplicity of the preparative procedure .     

MULTI-AGENT INFRASTRUCTURES FOR OBJECTIVE AND SUBJECTIVE COORDINATION

Coordination in multi-agented systems (MAS) can be conceived as either an agent activity (the subjective viewpoint) or an activity over agents (the objective viewpoint). The two viewpoints have generated two diverging and often contrasting lines of research, as well as different and noncompatible technologies, however, their integration is mandatory for modeling and engineering complex MAS. In this paper, we explore the issue of integration at both the model and the technology levels.

First, by taking FIPA agents and coordination artifacts as reference notions for subjective and objective approaches, respectively, we sketch a framework where agent interactions with coordination artifacts are modeled as physical acts, deliberated and executed by agents analogously to communicative actions. Then, we show how the JADE infrastructure for FIPA-compliant agents, and the TuCSoN infrastructure providing agents with coordination artifacts can be integrated at the technology level, allowing JADE agents to access TuCSoN tuple centers through JADE services.     

A Comparison of Inferences about Containers and Surfaces in Small-Scale and Large-Scale Spaces

Inference mechanisms about spatial relations constitute an important aspect of spatial reasoning as they allow users to derive unknown spatial information from a set of known spatial relations. When formalized in the form of algebras, spatial-relation inferences represent a mathematically sound definition of the behavior of spatial relations, which can be used to specify constraints in spatial query languages. Current spatial query languages utilize spatial concepts that are derived primarily from geometric principles, which do not necessarily match with the concepts people use when they reason and communicate about spatial relations. This paper presents an alternative approach to spatial reasoning by starting with a small set of spatial operators that are derived from concepts closely related to human cognition. This cognitive foundation comes from the behavior of image schemata, which are cognitive structures for organizing people's experiences and comprehension. From the operations and spatial relations of a small-scale space, a container–surface algebra is defined with nine basic spatial operators—inside, outside, on, off, their respective converse relations—contains, excludes, supports, separated_from, and the identity relation equal. The container–surface algebra was applied to spaces with objects of different sizes and its inferences were assessed through human-subject experiments. Discrepancies between the container–surface algebra and the human-subject testing appear for combinations of spatial relations that result in more than one possible inference depending on the relative size of objects. For configurations with small- and large-scale objects larger discrepancies were found because people use relations such as part of and at in lieu of in. Basic concepts such as containers and surfaces seem to be a promising approach to define and derive inferences among spatial relations that are close to human reasoning.     

PROPOSAL OF A PACKET SWITCH BASED ON PURELY RANDOM ROUTING

A new self-routing packet switching fabric architecture is presented, which avoids the use of electronic logic. This can be obtained by adopting a random routing procedure which can be simply implemented on available photonic devices. The results achieved for a 16 × 16 switching fabric demonstrate that either multicast or point-to-point traffic can be handled by the proposed switch indifferently.     

An approach to size effect in fatigue of metals using fractal theories

ABSTRACT As was experimentally observed by several authors, the fatigue strength of metallic materials decreases with increasing the specimen size. Such a decrease can be remarkable for very large structures like, for example, big cargo ships (some hundred meters long) transporting oil or other goods. Size effect in fatigue is herein explained by considering the fractal nature of the reacting cross sections of structures, that is, the renormalized fatigue strength is represented by a force amplitude acting on a surface with a fractal dimension lower than 2, where such a dimensional decrement depends on a self‐similar weakening of the material ligament, owing to the presence of cracks, defects, voids and so forth (microscopic level). However, this decrement tends to progressively disappear with increasing the structure size (macroscopic level), i.e. the effect of the material microstructure on the macroscopic fatigue behaviour gradually vanishes for structures large enough with respect to a characteristic microstructural size, this phenomenon being defined as multifractality. A multifractal scaling law for fatigue limit of metals is proposed, and some experimental results are examined in order to show how to apply the theoretical approach presented.     

EFFECTS OF MALVIDIN-3,5-DIGLUCOSIDE AND CYANIDIN CHLORIDE ON FOUR SALMONELLA SEROTYPES

SUMMARY— Reductions in numbers but no depression of respiration of 4 Salmonella serotypes over a 7.0-hr period was noted when they were incubated in the presence of anthocyanin pigments, malvidin-3.5diglucoside or cyanidin chloride. At certain concentrations of these pigments in the presence of glucose, stimulation of the respiration of some serotypes was evident. Slight reductions in cell numbers were noted as concentrations of malvidin-3,5-diglucoside increased. Comparable counts were obtained upon plating the cells on minimal and complete media, indicating lack of metabolic damage to those cells present. An enzyme assay utilizing the respiration of Saccharomyces cerevisiae var. ellipsoideus indicated the possibility of an anthocyanase in the cells which had been preincubated in the presence of the diglucoside of malvidin without glucose but not with glucose. If this observation were substantiated, it would indicate the production of a glucose-repressible anthocyanase. No evidence was obtained to indicate utilization of the aglycone by any of the 4 serotypes.     

PROPERTIES OF PEPSIN AND TRYPSIN ISOLATED FROM THE DIGESTIVE TRACT OF PARONA SIGNATA "PALOMETA"

Two digestive proteases from Parona signata (Palometa) were isolated from gastric and pyloric caeca tissues and characterized. The stomach enzyme was inhibited by pepstatin and was classified as pepsin. Palometa pepsin purified from a Sephadex G-100 column appeared as two bands on an SDS-PAGE gel and exhibited optimum activity at pH 3.5, and 37C. Palometa pepsin was inhibited by pepstatin to a similar exient as porcine pepsin. An enzyme isolated from the pyloric caeca was shown to be trypsin based on its molecular weight, its ability to hydrolyze the synthetic substrates, N-α-benzoyl-arginine-p-nitroanilide (BAPA), and tosyl-arginine methyl ester (TAME) and inhibition by the known trypsin inhibitors, SBTI, TLCK, PMSF and benzamidine. The purified trypsin from palometa pyloric caeca yielded a single band with a molecular mass of 24 kDa. Optima trypsin activity was obtained at pH 8.5 and the enzyme was stable over a pH range of 3 to 11. Palometa trypsin activity was stable for 30 min at 50C, but lost 50% of its activity after 30 min at 60C. The optimum temperature for activity was 65C. The biochemical properties of Palometa trypsin and pepsin were discussed in relation to the varying environment of Palometa in the Rio de la Plata estuary.     

CHARACTERIZATION OF TRYPSIN PURIFIED FROM THE PYLORIC CAECA OF THE SOUTHWEST ATLANTIC WHITE CROAKER Micropogonias furnieri (Sciaenidae)

A southwest Atlantic croaker protease was purified from the pyloric caeca by ammonium sulfate fractionation, acetone precipitation and affinity chromatography. The enzyme was classified as a trypsin on the basis of molecular weight, its ability to hydrolyze synthetic substrates N-α-benzoyl-arginine-p-nitroanilide (BAPA) and tosylarginine methyl ester (TAME), and its inhibition by known trypsin inhibitors. The isolated enzyme has a single band on SDS-PAGE with an estimated molecular mass of 24 kDa. Croaker trypsin activity was stable between pH 5 and pH 11 for 30 min at 0C, 10C and 25C and its maximal activity against BAPA was at pH 9.5. Thermostability was observed to about 55C for 30 min at pH 7.8 and its temperature optimum was 60C. Substrate turnover number was 850 BAPA units per μmol trypsin, and the K_mwas 0.081 mM at 25C. For the hydrolysis of TAME, V_maxwas 9273 units per μmol trypsin and the K_m was 0.155 mM at 25C. The catalytic efficiency V_max/K_mwas higher than that of trypsin from fish living in colder waters.