Restoration of RecA protein activity by genetic complementation

Summary Bacteria carrying either recA430 or recA453-441 mutations are sensitive to UV-irradiation since they amplify the synthesis of RecA protein either poorly or not at all. We show here that, in a recA453-441 (recA430) heterodiploid, UV-resistance and amplification of RecA430 protein were restored, indicating that the cellular level of RecA-associated protease activity was high enough to inactivate LexA repressor. Prophage 434 repressor was also extensively inactivated, whereas RecA430 protein alone cannot cleave this substrate. On the other hand, during growth of the recA453-441(recA430) heterodiploid at 42° C in the presence of adenine, a treatment activating only RecA441 protein, RecA441 protease activity was as high as in a recA441 haploid. In contrast, following this inducing treatment, there was no complementation between RecA441 and RecA⁺ proteins in a recA453-441(recA ⁺) heterodiploid. These results indicate that multimerization of RecA protein molecules results in a functional interaction that, in some combination between RecA protein subunits, may enhance RecA-associated protease activity.Obra Social de la Caja de Ahorros de Valencia     

Diel movement of smallmouth yellowfish Labeobarbus aeneus in the Vaal River,South Africa

Diel movements of Orange–Vaal smallmouth yellowfish Labeobarbus aeneus (Burchell, 1822) in the Vaal River, South Africa, were determined by externally attaching radio transmitters to 11 adult fish and manually tracking them between March and May 2012. Twenty-four radio telemetry monitoring surveys produced 2 304 diel tracks. At night, yellowfish displayed a preference for slow shallow (<0.3?m s?1, <0.5?m) and fast shallow habitats (>0.3?m s?1, <0.3?m), whereas by day they avoided these habitats, preferring fast deep areas (>0.3?m s?1, >0.3?m). The average total distance of 272?m moved per 24-hour period was three times greater than the diel range, and the average maximum displacement per minute was significantly higher in daytime (4?m) than at night (1.5?m). These findings suggest that L. aeneus is active primarily during the day in fast-flowing, deeper waters, and relatively inactive at night, when it occupies shallower habitats. This behaviour should be further explored to identify causal mechanisms underlying the diel habitat shifts in this species such as water temperature, foraging tactics and/or predator avoidance.     

Defensive insect symbiont leads to cascading extinctions and community collapse

Animals often engage in mutualistic associations with microorganisms that protect them from predation, parasitism or pathogen infection. Studies of these interactions in insects have mostly focussed on the direct effects of symbiont infection on natural enemies without studying community‐wide effects. Here, we explore the effect of a defensive symbiont on population dynamics and species extinctions in an experimental community composed of three aphid species and their associated specialist parasitoids. We found that introducing a bacterial symbiont with a protective (but not a non‐protective) phenotype into one aphid species led to it being able to escape from its natural enemy and increase in density. This changed the relative density of the three aphid species which resulted in the extinction of the two other parasitoid species. Our results show that defensive symbionts can cause extinction cascades in experimental communities and so may play a significant role in the stability of consumer‐herbivore communities in the field.     

Influence of Osmolarity and the Presence of an Osmoprotectant on Lactococcus lactis Growth and Bacteriocin Production

Growth inhibition of Lactococcus lactis provoked by increasing osmolarity is reversed when glycine betaine (GB) or its analogs are added to a defined medium. Lacticin 481 production increased sharply with growth medium osmolarity in the absence of osmoprotectant but remained unaffected when GB was supplied in media of increasing osmolarity.     

Development of a PCR Assay for Detection of Yersinia ruckeri in Tissues of Inoculated and Naturally Infected Trout

A PCR-based method was developed for the specific detection of Yersinia ruckeri in tissues of inoculated trout and naturally infected trout. No amplification products were obtained with other yersiniae, bacterial fish pathogens, or phylogenetically related bacteria (n = 34). The sensitivity of PCR detection was 60 to 65 bacterial cells per PCR tube, which was decreased to 10 to 20 cells by hybridization with a nonradioactive probe. The PCR assay proved to be as reliable as and faster than the conventional culture method for the detection of Y. ruckeri in infected trout tissues.     

Feasibility study of biogas upgrading coupled with nutrient removal from anaerobic effluents using microalgae-based processes

The present research was conducted to simultaneously optimize biogas upgrading and carbon and nutrient removal from centrates in a 180-L high-rate algal pond interconnected to an external CO₂ absorption unit. Different biogas and centrate supply strategies were assessed to increase biomass lipid content. Results showed 99 % CO₂ removal efficiencies from simulated biogas at liquid recirculation rates in the absorption column of 9.9 m³ m^?2 h^?1, concomitant with nitrogen and phosphorus removal efficiencies of 100 and 82 %, respectively, using a 1:70 diluted centrate at a hydraulic retention time of 7 days. The lipid content of the harvested algal–bacterial biomass remained low (2.9–11.2 %) regardless of the operational conditions, with no particular trend over time. The good settling characteristics of the algal–bacterial flocs resulted in harvesting efficiencies over 95 %, which represents a cost-effective alternative for algal biomass reutilization compared to conventional physical–chemical techniques. Finally, high microalgae biodiversity was found regardless of the operational conditions.