Mathematical description of bikaverin production in a fluidized bed bioreactor

Summary  Growth of Gibberella fujikuroi in submerged cultures occurs as micelles or filamentous hyphae dispersed in fluid and pellets or stable, spherical agglomerations. Gibberella fujikuroi growth, substrate consumption and bikaverin production kinetics obtained from submerged batch fermentation were fitted to three different sigmoid models: two and three-parameter Gompertz models and one Logistic model. Growth fitting was used to compare between models and select the best one by means of an F test. The best model for describing growth was the two-parameter Gompertz model and was used for glucose consumption and bikaverin production fitting. Data from eight different schemes of fermentations were analysed and parameter estimation was carried out by means of minimization of residual sum of squares. Some characteristic values obtained with the two-parameter Gompertz model fit are: μ=0.028 h⁻¹, Y_x/s=0.1089 g substrate/g biomass, α =0.1384 g product/g biomass.     

Distribution of cytoplasmically inherited bacteria Spiroplasma causing female bias in the Eurasian populations of Adalia bipunctata

Two-spot ladybirds Adalia bipunctata were collected from the populations of Western and Eastern Europe and Central Asia. The agent killing males at the early embryonic stage in these populations was identified as bacteria of the genus Spiroplasma. Bacteria found in A. bipunctata proved to be phylogenetically related to Spiroplasma ixodetis (typical line Y-32) found in tick Ixodes pacificus but not to Spiroplasma causing the death of male embryos in Drosophila.     

Length–weight relationships for 13 fish species in the Tangwang River,a tributary of Songhua River,China

The present work provides length–weight relationships (LWRs) for 13 fish species belonging to six families. The fishes were collected with gill nets (mesh sizes 10, 20, 40, 60, 90, 120 mm) and set nets (5, 8, 10 mm mesh sizes) from April 2012 to September 2015.     

Impact of Stock Market Structure on Intertrade Time and Price Dynamics

We analyse times between consecutive transactions for a diverse group of stocks registered on the NYSE and NASDAQ markets, and we relate the dynamical properties of the intertrade times with those of the corresponding price fluctuations. We report that market structure strongly impacts the scale-invariant temporal organisation in the transaction timing of stocks, which we have observed to have long-range power-law correlations. Specifically, we find that, compared to NYSE stocks, stocks registered on the NASDAQ exhibit significantly stronger correlations in their transaction timing on scales within a trading day. Further, we find that companies that transfer from the NASDAQ to the NYSE show a reduction in the correlation strength of transaction timing on scales within a trading day, indicating influences of market structure. We also report a persistent decrease in correlation strength of intertrade times with increasing average intertrade time and with corresponding decrease in companies'' market capitalization–a trend which is less pronounced for NASDAQ stocks. Surprisingly, we observe that stronger power-law correlations in intertrade times are coupled with stronger power-law correlations in absolute price returns and higher price volatility, suggesting a strong link between the dynamical properties of intertrade times and the corresponding price fluctuations over a broad range of time scales. Comparing the NYSE and NASDAQ markets, we demonstrate that the stronger correlations we find in intertrade times for NASDAQ stocks are associated with stronger correlations in absolute price returns and with higher volatility, suggesting that market structure may affect price behavior through information contained in transaction timing. These findings do not support the hypothesis of universal scaling behavior in stock dynamics that is independent of company characteristics and stock market structure. Further, our results have implications for utilising transaction timing patterns in price prediction and risk management optimization on different stock markets.     

Silicon amelioration of aluminium toxicity in teosinte (Zea mays L. ssp. mexicana)

The influence of different Al concentrations, (0, 60 and 120 M Al) on growth and internal concentrations of Al, Si and selected organic acids was analysed in plants of teosinte (Zea mays L. ssp. mexicana), a wild form of maize from acid soils from Mexico. The plants were grown in nutrient solutions (pH 4.0) with or without 4 M silicon. Analysis with the GEOCHEM speciation program did not reveal differences between free activities of Al³⁺ in solutions with and without 4 M Si, but solutions with Si yielded lower concentrations of monomeric Al species, [Al]_mono, when analysed by a modified aluminon method. Plants grown on solutions with similar [Al]_mono, but differing in silicon, showed highly significant differences in growth and tissue concentrations of Al and organic acids. Silicon prevented growth inhibition at [Al]_mono concentrations as high as 35 M, while plants grown without Si suffered severe growth reductions with 33 M [Al]_mono. In solutions with similar [Al]_mono concentrations plants with Si had lower tissue Al concentrations and higher concentrations of malic acid than plants without Si. In view of both the significant influence of Si on the response of plants to Al toxicity and the fact that some soluble Si is always present in soil solutions, the addition of low Si concentrations to nutrient solutions used for Al-tolerance screening is recommended.     

Seasonal abundance of two armyworm species, Spodoptera exitgua (Hübner) and Spodoptera litura (F.) in the Philippines

The two armyworm species Spodoptera exigua (Hübner) and S. litura (F.) are Important pests on several agricultural crops in the tropics. Knowledge about species abundance is important for the development of integrated pest management strategies. During 1998 and 1999 population densities were recorded weekly using pheromone traps at San Leonardo and Munoz (Province Nueva Ecija, 150 km north of Metro Manila) on the Philippine island Luzon. Furthermore, meteorological conditions and natural enemies were observed. Both armyworm species were present year-round at both observation sites. No differences in numbers of male insects trapped in pheromone traps between seasons were found for S. litura. Contrary, numbers of male S. exigua trapped during rainy season was significant higher than during dry season. Rainfall explained between 30 and 40% of trapped moths and has to be considered when monitoring population density with pheromone traps. Parasitism rates were below 5% in both years and for both species and can not explain the high variation observed in population densities.     

Glutamylsulfamoyladenosine and pyroglutamylsulfamoyladenosine are competitive inhibitors of E. coli glutamyl-tRNA synthetase

5'-O-[N-(L-glutamyl)-sulfamoyl] adenosine is a potent competitive inhibitor of E. coli glutamyl-tRNA synthetase with respect to glutamic acid (K(i) = 2.8 nM) and is the best inhibitor of this enzyme. It is a weaker inhibitor of mammalian glutamyl-tRNA synthetase (K(i) = 70 nM). The corresponding 5'-O-[N-(L-pyroglutamyl)-sulfamoyl] adenosine is a weak inhibitor (K(i) = 15 microM) of the E. coli enzyme.     

Vaccination with the Leishmania infantum ribosomal proteins induces protection in BALB/c mice against Leishmania chagasi and Leishmania amazonensis challenge

Leishmania chagasi and Leishmania amazonensis are the etiologic agents of different clinical forms of human leishmaniasis in South America. In an attempt to select candidate antigens for a vaccine protecting against different Leishmania species, the efficacy of vaccination using Leishmania ribosomal proteins and saponin as adjuvant was examined in BALB/c mice against challenge infection with both parasite species. Mice vaccinated with parasite ribosomal proteins purified from Leishmania infantum plus saponin showed a specific production of IFN-γ, IL-12 and GM-CSF after in vitro stimulation with L. infantum ribosomal proteins. Vaccinated mice showed a reduction in the liver and spleen parasite burdens after L. chagasi infection. After L. amazonensis challenge, vaccinated mice showed a decrease of the dermal pathology and a reduction in the parasite loads in the footpad and spleen. In both models, protection was correlated to an IL-12-dependent production of IFN-γ by CD4⁺ and CD8⁺ T cells that activate macrophages for the synthesis of NO. In the protected mice a decrease in the parasite-mediated IL-4 and IL-10 responses was also observed. In mice challenged with L. amazonensis, lower levels of anti-parasite-specific antibodies were detected. Thus, Leishmania ribosomal proteins plus saponin fits the requirements to compose a pan-Leishmania vaccine.     

Exploration of Phytoconstituents from Mussaenda roxburghii and Studies of Their Antibiofilm Effect

In the context of ethno botanical importance with no phytochemical investigations, Mussaenda roxburghii have been investigated to explore it's phytoconstituents and studies of their antibiofilm activity. Four compounds have been isolated from the aerial parts of this plant and were characterized as 2α,3β,19α,23‐tetrahydroxyurs‐12‐en‐28‐oic acid ( 1 ), β‐sitosterol glucoside ( 4 ), lupeol palmitate ( 5 ), and myoinositol ( 6 ). All these compounds were tested for antibacterial and antibiofilm activity against Pseudomonas aeruginosa. Compound 1 exhibited three times more antibiofilm activity with minimum inhibitory concentration (MIC) at 0.74 mm compared to that of streptomycin. Molecular docking studies exhibited a very high binding affinity of 1 with P. aeruginosa quorum sensing proteins and motility associated proteins viz. LasR and PilB, PilY1, PilT, respectively. Compound 1 was also found to be non‐cytotoxic against sheep RBC and murine peritoneal macrophages at selected sub‐MIC doses.     

Towards the establishment of a porcine model to study human amebiasis

Background

Entamoeba histolytica is an important parasite of the human intestine. Its life cycle is monoxenous with two stages: (i) the trophozoite, growing in the intestine and (ii) the cyst corresponding to the dissemination stage. The trophozoite in the intestine can live as a commensal leading to asymptomatic infection or as a tissue invasive form producing mucosal ulcers and liver abscesses. There is no animal model mimicking the whole disease cycle. Most of the biological information on E. histolytica has been obtained from trophozoite adapted to axenic culture. The reproduction of intestinal amebiasis in an animal model is difficult while for liver amebiasis there are well-described rodent models. During this study, we worked on the assessment of pigs as a new potential model to study amebiasis.

Methodology/Principal Findings

We first co-cultured trophozoites of E. histolytica with porcine colonic fragments and observed a disruption of the mucosal architecture. Then, we showed that outbred pigs can be used to reproduce some lesions associated with human amebiasis. A detailed analysis was performed using a washed closed-jejunal loops model. In loops inoculated with virulent amebas a severe acute ulcerative jejunitis was observed with large hemorrhagic lesions 14 days post-inoculation associated with the presence of the trophozoites in the depth of the mucosa in two out four animals. Furthermore, typical large sized hepatic abscesses were observed in the liver of one animal 7 days post-injection in the portal vein and the liver parenchyma.

Conclusions

The pig model could help with simultaneously studying intestinal and extraintestinal lesion development.