Spectrophotometric quantification of lactic bacteria in alginate and control of cell release with chitosan coating

Lactococcus lactis ssp. cremoris was entrapped within a Ca-alginate matrix, and an in situ spectrophotometric method for monitoring cell population in calcium alginate beads described. The intracapsular cell population can be estimated by measuring the optical density of beads containing cells, using cell-free beads as reference, or by measuring absorbance of a liquified bead suspension. Alginate beads, and beads coated with chitosan type I, II, and I and II mixtures, were examined for cell release. Lower viscosity chitosan (type I) coatings reduced cell release by a factor of 100 from10⁵ cfu ml⁻¹ to 10³ cfu ml⁻¹ after 6 h of fermentation. Reuse of chitosan I coated alginate beads also showed a reduction in cell release by a factor of 100. Cell loading and initial cell growth within the beads greatly affected cell release. Reducing the initial cell release would lower the overall levels of cell release throughout the fermentation. Compared to non-immobilized cultures, a 20–40% reduction in the lactic acid production rate was observed for alginate beads and chitosan I coated alginate beads, respectively. This reduction can be compensated for by increasing the intracapsular cell loading during immobilization, or before the onset of fermentation.     

Reassessment of the vocal repertoire of a nest-building gladiator frog,Boana pardalis (Anura,Hylidae, Cophomantinae): implications for its diagnosis within the B. faber species group

In this study, we re-describe the advertisement and territorial calls of Boana pardalis, carry out an acoustic comparison between the studied species and the other congeners of the B. faber group, and report for the first time the tympanic amplexus for the studied species. The advertisement call of B. pardalis can be used to supplement its diagnosis in the B. faber group based on temporal call traits, e.g. emission rate and emission pattern, as well as the call envelope.     

Reduced Global Genetic Differentiation of Exploited Marine Fish Species

Knowledge on genetic structure is key to understand species connectivity patterns and to define the spatiotemporal scales over which conservation management plans should be designed and implemented. The distribution of genetic diversity (within and among populations) greatly influences species ability to cope and adapt to environmental changes, ultimately determining their long-term resilience to ecological disturbances. Yet, the drivers shaping connectivity and structure in marine fish populations remain elusive, as are the effects of fishing activities on genetic subdivision. To investigate these questions, we conducted a meta-analysis and compiled genetic differentiation data (F_ST/Φ_ST estimates) for more than 170 fish species from over 200 published studies globally distributed. We modeled the effects of multiple life-history traits, distance metrics, and methodological factors on observed population differentiation indices and specifically tested whether any signal arising from different exposure to fishing exploitation could be detected. Although the myriad of variables shaping genetic structure makes it challenging to isolate the influence of single drivers, results showed a significant correlation between commercial importance and genetic structure, with widespread lower population differentiation in commercially exploited species. Moreover, models indicate that variables commonly used as proxy for connectivity, such as larval pelagic duration, might be insufficient, and suggest that deep-sea species may disperse further. Overall, these results contribute to the growing body of knowledge on marine genetic connectivity and suggest a potential effect of commercial fisheries on the homogenization of genetic diversity, highlighting the need for additional research focused on dispersal ecology to ensure long-term sustainability of exploited marine species.     

Plasmodium chabaudi: Expression of active recombinant chabaupain-1 and localization studies in Anopheles sp.

Plasmodium cysteine proteases have been shown to be immunogenic and are being used as malaria potential serodiagnostic markers and vaccine targets. Genes encoding two Plasmodium chabaudi cysteine proteases chabaupain-1 (CP-1) and chabaupain-2 (CP-2) were identified and further expressed in Escherichia coli. Solubilisation of recombinant CP-1 and CP-2 was achieved by decreasing the temperature of induction.Anopheles gambiae tissues infected with Plasmodium were analyzed by Western blotting using the anti-CP-1 antibody showing that CP-1 is only present in the A. gambiae midguts being absent from other infected mosquito biological material. Anti-CP-1 anti-serum recognized a 30 kDa band in P. chabaudi, Plasmodium berghei and Plasmodium yoelii lysates but does not recognize the recombinant CP-2 extracts suggesting high antibody specificity.     

Modelling the influence of nutrient loads on Portuguese estuaries

The effects of implementing Directive 91/271/EEC of 21 May 1991 (Waste Water Treatment Plan Directive) and Directive 91/676/EEC of 12 December (Nitrates Directive) are analysed in 7 Portuguese estuaries (Minho, Lima, Douro, Mondego, Tagus, Sado and Guadiana) and two coastal lagoons (Ria de Aveiro and Ria Formosa), with a modelling approach. MOHID Water Modelling System was used to perform simulations with three nitrogen load scenarios for each system: a reference scenario, a 50% nitrate removal by agriculture scenario and another with a 100% nutrients removal by waste water treatment plants (WWTP). It is shown that the interaction between hydrodynamic and ecological processes is an important feature to study trophic problems in estuaries. Ecological processes such as primary production only occur inside the system if the residence time of water is high enough to enable organismal activity and if the adequate conditions are found (e.g. light, nutrients, temperature). From the model results it is possible to conclude: (i) in systems with short residence time a reduction in nutrient load will only produce a decrease in nutrient transit and will not affect the system’s global ecological status (e.g. Douro Estuary); (ii) in systems with long residence time the effects will range from significant, when primary production is mostly limited by nutrients (e.g. Ria de Aveiro), to non-significant, when primary production in the system is light-limited (e.g. Tagus Estuary).     

Host-Parasite Interactions in Chagas Disease: Genetically Unidentical Isolates of a Single Trypanosoma cruzi Strain Identified In Vitro via LSSP-PCR

The present study aims at establishing whether the diversity in pathogenesis within a genetically diverse host population infected with a single polyclonal strain of Trypanosoma cruzi is due to selection of specific subpopulations within the strain. For this purpose we infected Swiss mice, a genetically diverse population, with the polyclonal strain of Trypanosoma cruzi Berenice-78 and characterized via LSSP-PCR the kinetoplast DNA of subpopulations isolated from blood samples collected from the animals at various times after inoculation (3, 6 and 12 months after inoculation). We examined the biological behavior of the isolates in acellular medium and in vitro profiles of infectivity in Vero cell medium. We compared the characteristics of the isolates with the inoculating strain and with another strain, Berenice 62, isolated from the same patient 16 years earlier. We found that one of the isolates had intermediate behavior in comparison with Berenice-78 and Berenice-62 and a significantly different genetic profile by LSSP-PCR in comparison with the inoculating strain. We hereby demonstrate that genetically distinct Trypanosoma cruzi isolates may be obtained upon experimental murine infection with a single polyclonal Trypanosoma cruzi strain.