Blue-light-mediated shade avoidance requires combined auxin and brassinosteroid action in Arabidopsis seedlings

Plant growth in dense vegetation can be strongly affected by competition for light between neighbours. These neighbours can not only be detected through phytochrome-mediated perception of a reduced red:far-red ratio, but also through altered blue light fluence rates. A reduction in blue light (low blue) induces a set of phenotypic traits, such as shoot elongation, to consolidate light capture; these are called shade avoidance responses. Here we show that both auxin and brassinosteroids (BR) play an important role in the regulation of enhanced hypocotyl elongation of Arabidopsis seedlings in response to blue light depletion. Only when both hormones are experimentally blocked simultaneously, using mutants and chemical inhibitors, will the response be fully inhibited. Upon exposure to low blue several members of the cell wall modifying XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE (XTH) protein family are regulated as well. Interestingly, auxin and BR each regulate a subset of these XTHs, by which they could regulate cell elongation. We hypothesize that auxin and BR regulate specific XTH genes in a non-redundant and non-synergistic manner during low-blue-induced shade avoidance responses of Arabidopsis seedlings, which explains why both hormones are required for an intact low-blue response.     

Whole-cell hydroxylation of n-octane by Escherichia coli strains expressing the CYP153A6 operon

CYP153A6 is a well-studied terminal alkane hydroxylase which has previously been expressed in Pseudomonas putida and Escherichia coli by using the pCom8 plasmid. In this study, CYP153A6 was successfully expressed in E. coli BL21(DE3) by cloning the complete operon from Mycobacterium sp. HXN-1500, also encoding the ferredoxin reductase and ferredoxin, into pET28b(+). LB medium with IPTG as well as auto-induction medium was used to express the proteins under the T7 promoter. A maximum concentration of 1.85?μM of active CYP153A6 was obtained when using auto-induction medium, while with IPTG induction of LB cultures, the P450 concentration peaked at 0.6–0.8?μM. Since more biomass was produced in auto-induction medium, the specific P450 content was often almost the same, 0.5–1.0?μmol P450 g _DCW ^?1 , for both methods. Analytical scale whole-cell biotransformations of n-octane were conducted with resting cells, and it was found that high P450 content in biomass did not necessarily result in high octanol production. Whole cells from LB cultures induced with IPTG gave higher specific and volumetric octanol formation rates than biomass from auto-induction medium. A maximum of 8.7?g octanol L _BRM ^?1 was obtained within 24?h (0.34?g L _BRM ^?1 ?h^?1) with IPTG-induced cells containing only 0.20?μmol P450 g _DCW ^?1 , when glucose (22?g L _BRM ^?1 ) was added for cofactor regeneration.     

Genetic variation in the β2-adrenocepter gene is associated with susceptibility to bacterial meningitis in adults

Recently, the biased β2-adrenoceptor/β-arrestin pathway was shown to play a pivotal role in crossing of the blood brain barrier by Neisseria meningitidis. We hypothesized that genetic variation in the β2-adrenoceptor gene (ADRB2) may influence susceptibility to bacterial meningitis. In a prospective genetic association study we genotyped 542 patients with CSF culture proven community acquired bacterial meningitis and 376 matched controls for 2 functional single nucleotide polymorphisms in the β2-adrenoceptor gene (ADRB2). Furthermore, we analyzed if the use of non-selective beta-blockers, which bind to the β2-adrenoceptor, influenced the risk of bacterial meningitis. We identified a functional polymorphism in ADRB2 (rs1042714) to be associated with an increased risk for bacterial meningitis (Odds ratio [OR] 1.35, 95% confidence interval [CI] 1.04-1.76; p?=?0.026). The association remained significant after correction for age and was more prominent in patients with pneumococcal meningitis (OR 1.52, 95% CI 1.12-2.07; p?=?0.007). For meningococcal meningitis the difference in genotype frequencies between patients and controls was similar to that in pneumococcal meningitis, but this was not statistically significant (OR 1.43, 95% CI 0.60-3.38; p?=?0.72). Patients with bacterial meningitis had a lower frequency of non-selective beta-blockers use compared to the age matched population (0.9% vs. 1.8%), although this did not reach statistical significance (OR 1.96 [95% CI 0.88-4.39]; p?=?0.09). In conclusion, we identified an association between a genetic variant in the β2-adrenoceptor and increased susceptibility to bacterial meningitis. The potential benefit of pharmacological treatment targeting the β2-adrenoceptor to prevent bacterial meningitis in the general population or patients with bacteraemia should be further studied in both experimental studies and observational cohorts.     

Intracerebral Hemorrhages in Adults with Community Associated Bacterial Meningitis in Adults: Should We Reconsider Anticoagulant Therapy?

Objective

To study the incidence, clinical presentation and outcome of intracranial hemorrhagic complications in adult patients with community associated bacterial meningitis.

Methods

Nationwide prospective cohort study from all hospitals in the Netherlands, from 1 March 2006, through 31 December 2010.

Results

Of the 860 episodes of bacterial meningitis that were included, 24 were diagnosed with intracranial hemorrhagic complications: 8 upon presentation and 16 during clinical course. Clinical presentation between patients with or without intracranial hemorrhage was similar. Causative bacteria were Streptococcus pneumoniae in 16 patients (67%), Staphylococcus aureus in 5 (21%), Pseudomonas aeruginosa and Listeria monocytogenes both in 1 patient (4%). Occurrence of intracranial hemorrhage was associated with death (63% vs. 15%, P<0.001) and unfavorable outcome (94% vs. 34%, P<0.001). The use of anticoagulants on admission was associated with a higher incidence of intracranial hemorrhages (odds ratio 5.84, 95% confidence interval 2.17–15.76).

Conclusion

Intracranial hemorrhage is a rare but devastating complication in patients with community-associated bacterial meningitis. Since anticoagulant therapy use is associated with increased risk for intracranial hemorrhage, physicians may consider reversing or temporarily discontinuing anticoagulation in patients with bacterial meningitis.     

A feasibility study into adenosine triphosphate measurement in exhaled breath condensate: a potential bedside method to monitor alveolar deformation

Recent research suggested an important role for pulmonary extracellular adenosine triphosphate (ATP) in the development of ventilation-induced lung injury. This injury is induced by mechanical deformation of alveolar epithelial cells, which in turn release ATP to the extracellular space. Measuring extracellular ATP in exhaled breath condensate (EBC) may be a non-invasive biomarker for alveolar deformation. Here, we study the feasibility of bedside ATP measurement in EBC. We measured ATP levels in EBC in ten subjects before and after an exercise test, which increases respiratory parameters and alveolar deformation. EBC lactate concentrations were measured as a dilution marker. We found a significant increase in ATP levels in EBC (before 73 RLU [IQR 50–209] versus after 112 RLU [IQR 86–203]; p value 0.047), and the EBC ATP-to-EBC lactate ratio increased as well (p value 0.037). We present evidence that bedside measurement of ATP in EBC is feasible and that ATP levels in EBC increase after exercise. Future research should measure ATP levels in EBC during mechanical ventilation as a potential biomarker for alveolar deformation.     

Monk parakeet invasion success: a role for nest thermoregulation and bactericidal potential of plant nest material?

Invasive species are a global threat to biodiversity, economy and human wellbeing. To mitigate these threats, identifying and halting the introduction of potentially invasive species is crucial. Although progress has been made in elucidating mechanisms underlying invasion success, the role of species behavioral strategies has only received scant attention. Here, we use the invasion of monk parakeets in Santa Catarina state, southern Brazil to study whether behavioral strategies such as nest thermoregulation and the ability to self-medicate against pathogens contribute to the establishment success of invading species. We relate data on monk parakeet reproductive success to ambient temperatures in- and outside nesting chambers and test the bactericidal potential of plants transported to the nest by breeding monk parakeets. Compared to breeding data from other invaded ranges and parts of the species’ native range, our results suggest both thermoregulation and the use of bactericidal plants could potentially influence monk parakeet reproductive success. Thermoregulation maintains stable temperatures of incubator chambers compared to large fluctuations (especially hotter extremes) outside the nest. At least one of the plants brought to the nest effectively inhibited growth of pathogenic bacteria. The union of these two factors could increase reproductive rates and may consequently aid the expansion of the species in new non-native environments.     

A membrane-associated protein with Cr(VI)-reducing activity from Thermus scotoductus SA-01

A membrane-associated chromate reductase from Thermus scotoductus SA-01 has been purified to apparent homogeneity and shown to couple the reduction of Cr(VI) to NAD(P)H oxidation, with a preference towards NADH. The chromate reductase is a homodimer with a monomeric molecular weight of 48 kDa and a noncovalently bound FAD coenzyme. The enzyme is optimally active at a pH of 6.5 and 65 degrees C with a K(m) of 55.5+/-4.2 microM and a V(max) of 2.3+/-0.1 micromol Cr(VI) min(-1) mg(-1) protein. The catalytic efficiency (k(cat)/K(m)) of the enzyme was found to be comparable to that found for quinone reductases but more efficient than the nitroreductases. N-terminal sequencing and subsequent screening of a genomic library of T. scotoductus revealed an ORF of 1386 bp, homologous (84%) to the dihydrolipoamide dehydrogenase gene of Thermus thermophilus HB8. These results extend the knowledge of chromate reductases mediating Cr(VI) reduction via noncovalently bound or free redox-active flavin groups and the activity of dihydrolipoamide dehydrogenases towards physiologically unrelated substrates.