Experimental evidence for real-time song frequency shift in response to urban noise in a passerine bird

Research has shown that bird songs are modified in different ways to deal with urban noise and promote signal transmission through noisy environments. Urban noise is composed of low frequencies, thus the observation that songs have a higher minimum frequency in noisy places suggests this is a way of avoiding noise masking. Most studies are correlative and there is as yet little experimental evidence that this is a short-term mechanism owing to individual plasticity. Here we experimentally test if house finches (Carpodacus mexicanus) can modulate the minimum frequency of their songs in response to different noise levels. We exposed singing males to three continuous treatments: low–high–low noise levels. We found a significant increase in minimum frequency from low to high and a decrement from high to low treatments. We also found that this was mostly achieved by modifying the frequency of the same low-frequency syllable types used in the different treatments. When different low-frequency syllables were used, those sung during the noisy condition were longer than the ones sang during the quiet condition. We conclude that house finches modify their songs in several ways in response to urban noise, thus providing evidence of a short-term acoustic adaptation.     

Application of composted urban residue enhanced the performance of afforested shrub species in a degraded semiarid land

Improvement of physical-chemical soil quality is a key step for carrying out revegetation programs of degraded lands in Mediterranean semiarid areas. Organic residue addition may restore the quality of these areas. A field experiment was conducted in a silt-loam soil (Typic Petrocalcid) from a degraded semiarid Mediterranean area to evaluate the effect of the addition of a composted urban residue on soil aggregate stability, bulk density and chemical properties and on the establishment of Pistacia lentiscus and Retama sphaerocarpa seedlings. The composted residue was applied at a rate of 6.7 kg m(-2) before planting. The nutrient content (NPK), total organic C and water soluble C were increased and bulk density was decreased, in the rhizosphere soil of both shrub species, by the composted residue. The addition of composted residue significantly increased the soil aggregate stability by about 22% for both shrub species. The beneficial effect of the composted residue on soil quality still persisted 18 months after addition. Eighteen months after planting, the addition of composted residue to soil had increased significantly the production of shoot biomass by P. lentiscus and R. sphaerocarpa, by about 160% and 320% respectively, compared to control values. Composted residue addition to soil can be considered an effective preparation method of a degraded area for carrying out successful revegetation programs with Mediterranean shrubs under semiarid conditions.     

Effects of disturbance intensity and frequency on bacterial community composition and function

Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and 'disturbed' incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.     

Development of a bioadhesive nanoformulation with Glycyrrhiza glabra L. extract against Candida albicans

Abstract

Glycyrrhiza glabra L. is considered an important source of bioactive compounds. This study aimed at the development of an efficient solution for the treatment of oral candidiasis. Several extracts of Glycyrrhiza glabra L. were prepared using different solvents and their potential in vitro antifungal activity was assessed. Ethanolic extracts showed the most promising results against C. albicans. This extract was incorporated into mucoadhesive nanoparticles (PLA, PLGA and alginate), which were further included in an oral gel, an oral film and a toothpaste, respectively. The results showed that nanoparticles were successfully produced, presenting a mean size among 100–900?nm with high encapsulation efficiency. In vitro studies showed that the most bioadhesive formulation was the oral film with extract-loaded PLGA nanoparticles, followed by the toothpaste with extract-loaded alginate nanoparticles and the oral gel with extract-loaded PLA nanoparticles.     

Isolated and purified plasma and thylakoid membranes of the cyanobacteriumAnacystis nidulans contain immunologically cross-reactive aa3-type cytochrome oxidase

Cell-free extracts ofAnacystis nidulans were fractionated by discontinuous sucrose density gradient centrifugation resulting in the separation of two distinct types of membranes, the heavier one containing the chlorophyll and the lighter one devoid of chlorophyll. Identity of the latter with plasma membrane was confirmed by labeling of intact cells with impermeant marker,³⁵S-diazobenzenesulfonate, prior to cell disruption. Both membrane fractions were purified individually by repeated recentrifugation on identical gradients. Purified membranes were subjected to dissociating polyacrylamide gel electrophoresis, either type of membranes yielding a distinct polypeptide pattern. After transfer of the polypeptides to nitrocellulose by Western blotting, two of the proteins, with molecular weights of approximately 55,000 and 32,000, respectively, gave strong and specifically complementary cross-reactions with antibodies raised against subunits I and II of the aa₃-type cytochrome oxidase fromParacoccus denitrificans. The findings will be discussed in terms of the presence of aa₃-type cytochrome oxidase in both plasma and thylakoid membranes ofAnacystis nidulans.