Extracellular secretion of levansucrase from Zymomonas mobilis in Escherichia coli

Secretion of levansucrase from Zymomonas mobilis in Escherichiacoli by glycine supplement was investigated. A significant amount of levansucrase (about 25% of total activity) was found in intact whole-cells. Cell fractionation experiments showed that levansucrase was found both in the periplasmic space and in the cytoplasmic fraction of E. coli. None or only trace amounts of levansucrase was detected in the extracellular culture broth at 24 h of cultivation and it accrued with the increasing concentration of glycine in the culture medium and duration of the culture period. Optimal glycine concentration for the maximum secretion of levansucrase was in the range of 0.8-1%, in which approximately 20-50% of levansucrase was released into the extracellular fraction at 24 h of cultivation, although glycine retarded the bacterial growth.     

Plant intraspecific functional trait variation is related to within‐habitat heterogeneity and genetic diversity in Trifolium montanum L.

Intraspecific trait variation (ITV), based on available genetic diversity, is one of the major means plant populations can respond to environmental variability. The study of functional trait variation and diversity has become popular in ecological research, for example, as a proxy for plant performance influencing fitness. Up to now, it is unclear which aspects of intraspecific functional trait variation (iFD_CV) can be attributed to the environment or genetics under natural conditions. Here, we examined 260 individuals from 13 locations of the rare (semi‐)dry calcareous grassland species Trifolium montanum L. in terms of iFD_CV, within‐habitat heterogeneity, and genetic diversity. The iFD_CV was assessed by measuring functional traits (releasing height, biomass, leaf area, specific leaf area, leaf dry matter content, F_v/F_m, performance index, stomatal pore surface, and stomatal pore area index). Abiotic within‐habitat heterogeneity was derived from altitude, slope exposure, slope, leaf area index, soil depth, and further soil factors. Based on microsatellites, we calculated expected heterozygosity (H_e) because it best‐explained, among other indices, iFD_CV. We performed multiple linear regression models quantifying relationships among iFD_CV, abiotic within‐habitat heterogeneity and genetic diversity, and also between separate functional traits and abiotic within‐habitat heterogeneity or genetic diversity. We found that abiotic within‐habitat heterogeneity influenced iFD_CV twice as strong compared to genetic diversity. Both aspects together explained 77% of variation in iFD_CV ( = .77, F_{2, 10} = 21.66, p < .001). The majority of functional traits (releasing height, biomass, specific leaf area, leaf dry matter content, F_v/F_m, and performance index) were related to abiotic habitat conditions indicating responses to environmental heterogeneity. In contrast, only morphology‐related functional traits (releasing height, biomass, and leaf area) were related to genetics. Our results suggest that both within‐habitat heterogeneity and genetic diversity affect iFD_CV and are thus crucial to consider when aiming to understand or predict changes of plant species performance under changing environmental conditions.     

Severe and rapid population declines in exotic birds

A particularly vexing phenomenon within invasion ecology is the occurrence of spontaneous collapses within seemingly well-established exotic populations. Here, we assess the frequency of collapses among 68 exotic bird populations established in Hawaii, Puerto Rico, Los Angeles and Miami. Following other published definitions, we define a ‘collapse’ as a decline in abundance of ≥90 % within ≤10 years that lasts for at least 3 years. We show that 44 of the 68 exotic bird populations have exhibited declines at some point within their time series. Sixteen of the populations declined sufficiently to be defined as collapsed. It took on average 3.8 ± 1.8 years for populations to decline into a collapsed state, and this state persisted on average for 7.1 ± 6.3 years across (collapsed) populations. We compared the severity and duration of declines across all 44 declining populations according to taxonomic Order and geographic region. Neither variable explained substantial variation in the metrics of collapse. Our results indicate that severe, rapid, and persistent population declines may be common among exotic populations. We suggest that incorporating the probability and persistence of collapses into management decisions can inform efforts to enact control or eradication measures. We also suggest that applying our approach to other taxa and locations is crucial for improving our understanding of when and where collapses are likely to occur.     

The unpredictability of favourability: condition assessment and protected areas in England

The probability that protected areas will deliver their potential for maintaining or enhancing biodiversity is likely to be maximised if they are appropriately and effectively managed. As a result, governments and conservation agencies are devoting much attention to the management of protected areas. In the U.K., the demand for performance accountability has resulted in Public Service Agreements (PSA) that set out targets for government departments to deliver results in return for investments being made. One such target for England is to ensure that all nationally important wildlife sites are in favourable condition by 2010. Here, we tested the hypothesis, of potential strategic importance, that the ecological condition of these sites is predictable from relationships with a range of physical, environmental and demographic variables. We used binary logistic regression to investigate these relationships, using the results of English Nature’s 1997–2003 condition assessment exercise. Generally, sites in unfavourable condition tend to be larger in area, located at higher elevations, but with higher human population density and are more spatially isolated from units of the same habitat. However, despite the range of different parameters included in our models, the extent to which the condition of any given site could be predicted was low. Our results have implications for the delivery of PSA targets, funding allocation, and the location of new protected areas.     

A fast dynamic mode of the EF‐G‐bound ribosome

A key intermediate in translocation is an ‘unlocked state’ of the pre‐translocation ribosome in which the P‐site tRNA adopts the P/E hybrid state, the L1 stalk domain closes and ribosomal subunits adopt a ratcheted configuration. Here, through two‐ and three‐colour smFRET imaging from multiple structural perspectives, EF‐G is shown to accelerate structural and kinetic pathways in the ribosome, leading to this transition. The EF‐G‐bound ribosome remains highly dynamic in nature, wherein, the unlocked state is transiently and reversibly formed. The P/E hybrid state is energetically favoured, but exchange with the classical P/P configuration persists; the L1 stalk adopts a fast dynamic mode characterized by rapid cycles of closure and opening. These data support a model in which P/E hybrid state formation, L1 stalk closure and subunit ratcheting are loosely coupled, independent processes that must converge to achieve the unlocked state. The highly dynamic nature of these motions, and their sensitivity to conformational and compositional changes in the ribosome, suggests that regulating the formation of this intermediate may present an effective avenue for translational control.     

Immunological characterization of cytochrome H-450 in rat tissues

Rabbit antiserum produced against rat liver cytochrome H-450 was specific for cytochrome H-450. The antiserum did not react with hemolysate, microsomal and mitochondrial fractions of liver, and tissue extracts from heart, lung skeletal muscle, and testis of rat. With the monospecific antiserum, a rocket immunoelectrophoretic assay method was developed for the quantitation of the antigen with a sensitivity of 25 ng. By using rocket immunoelectrophoresis, the total amounts of the antigen found in liver, kidney, and brain of 20 rats were 33.6, 3.6, and 1.3 mg, respectively. It appears that the antigens in liver, kidney, and brain are immunologically identical. From immunological studies with subcellular fractions of rat liver, the antigen was found only in the postmicrosomal fraction. This indicates that the antigen is not a precursor or a proteolytic product of known cytochromes in mitochondria or microsomes. Therefore, cytochrome H-450 is a unique cytosolic protein found in brain, kidney, and liver.