Asymmetric response of Amazon forest water and energy fluxes to wet and dry hydrological extremes reveals onset of a local drought-induced tipping point

Understanding the effects of intensification of Amazon basin hydrological cycling—manifest as increasingly frequent floods and droughts—on water and energy cycles of tropical forests is essential to meeting the challenge of predicting ecosystem responses to climate change, including forest “tipping points”. Here, we investigated the impacts of hydrological extremes on forest function using 12+ years of observations (between 2001–2020) of water and energy fluxes from eddy covariance, along with associated ecological dynamics from biometry, at the Tapajós National Forest. Measurements encompass the strong 2015–2016 El Niño drought and La Niña 2008–2009 wet events. We found that the forest responded strongly to El Niño-Southern Oscillation (ENSO): Drought reduced water availability for evapotranspiration (ET) leading to large increases in sensible heat fluxes (H). Partitioning ET by an approach that assumes transpiration (T) is proportional to photosynthesis, we found that water stress-induced reductions in canopy conductance (G_s) drove T declines partly compensated by higher evaporation (E). By contrast, the abnormally wet La Niña period gave higher T and lower E, with little change in seasonal ET. Both El Niño-Southern Oscillation (ENSO) events resulted in changes in forest structure, manifested as lower wet-season leaf area index. However, only during El Niño 2015–2016, we observed a breakdown in the strong meteorological control of transpiration fluxes (via energy availability and atmospheric demand) because of slowing vegetation functions (via shutdown of G_s and significant leaf shedding). Drought-reduced T and G_s, higher H and E, amplified by feedbacks with higher temperatures and vapor pressure deficits, signaled that forest function had crossed a threshold, from which it recovered slowly, with delay, post-drought. Identifying such tipping point onsets (beyond which future irreversible processes may occur) at local scale is crucial for predicting basin-scale threshold-crossing changes in forest energy and water cycling, leading to slow-down in forest function, potentially resulting in Amazon forests shifting into alternate degraded states.     

Influence of growth phase and carbon source on the content of rubredoxin in Acinetobacter calcoaceticus

The rubredoxin content of Acinetobacter calcoaceticus in dependence on the carbon source (acetate, n-alkanes, succinate, L-malate) and on the growth phase was studied by means of a radioimmunoassay. The method used was specific for rubredoxin from Acinetobacter calcoaceticus. The formation of rubredoxin increased with time up to the end of the logarithmic phase when n-alkanes were the sole carbon source. After growth of Acinetobacter calcoaceticus on non-hydrocarbon substrates, rubredoxin was not detected.     

Shift work and sex are variants across Karolinska Sleep Questionnaire and the application of linking analysis as a step forward using Item Response Theory

The frequency of sleep disturbances is considerably higher in the night and shift workers and in females than in day workers and males, respectively. However, a subjective sleep scale must be invariant across these groups, independently of the level of their members on the scale. This study is aimed to test the invariance of the Karolinska Sleep Questionnaire’s (KSQ) items by shift work and sex. We used the data from a census that covered more than 90% (N = 1648) of the nurses from the main institute of the largest public hospital complex of Brazil. Firstly, we intend to find the KSQ’s dimensionality using factorial analysis and Item Response Theory (IRT) performed by Graded Response Model. Differential Item Functioning (DIF) was the technique used to test the invariance of each KSQ’s dimensions. In case of variance detection, we applied the linking analysis. Intending to test the KSQ’s consistency with external variables, we assessed correlations between KSQ’s dimensions with health variables, i.e., self-reported health status and musculoskeletal pain. We have found one scale and two subscales from one general and another bidimensional factor structure of the KSQ, respectively. In these dimensions, the KSQ’s items fitted well to the IRT and we have identified DIF by shift work. However, we have found DIF by sex just in one item on the general factor. Linking analysis showed as a possible step forward in the variance issue placing on to the same scale the shift work groups in the items with DIF. All correlations between KSQ’s dimensions with health variables were significant. Our findings allow us to argue that KQS’s items were variant by shift work and sex in a nursing staff census from the largest public hospital complex of Brazil, but we can go on using linking analysis. This could be used as an evidence for the construct validity should go beyond the traditional dimensionality assessment. The dimensionalities of KSQ fit well for other population but individuals living in Scandinavian countries.     

Mechanoreceptive function of pectines in the Brazilian yellow scorpion Tityus serrulatus: perception of substrate-borne vibrations and prey detection

Environment perception by scorpions is an issue of great interest, and there is controversy about the use of pectines in this function. This paper investigates the mechanoreceptive function of pectines of the yellow scorpion Tityus serrulatus. The study was conducted in laboratory conditions from July 2003 to July 2004. Ninety females were maintained in six terraria (N = 15). Three of them were named “control” group (intact pectines) and the others “treatment” group (pectines covered with paraffin). Three experimental tests (an ethogram, a test of prey detection and a test of perception of substrate-borne vibrations) were performed to compare skills of animals with and without blocked pectines. The ethogram showed that treated individuals significantly reduced their exploratory activities, spent more time resting, and aggregated more than the control ones. Prey detection tests showed that the blocking of pectines made the yellow scorpions inefficient to detect and capture prey. Vibration tests showed that animals with blocked pectines also did not respond to the vibrations produced in the substrate, whereas the opposite occurred with the control group. These results suggest a mechanoreceptive function for T. serrulatus pectines, and show that the detection of ground vibrations by these structures is important for prey perception and orientation in the Brazilian yellow scorpion.     

Rubredoxin reductase in crude extracts of Acinetobacter calcoaceticus in relation to carbon source and growth phase

By immunization of rabbits with discelectrophoretically purified rubredoxin-reductase from Ac. calcoaceticus an antiserum against this enzyme was prepared. The antiserum was monospecifical to a diaphoretic activity, which had a RF-value identical with the rubredoxin-reductase-RF value. It has been shown by discelectrophoresis, immunoelectrophoresis, OUCHTERLONY technique and kinetic investigations that crude extracts of bacteria grown on C16, malate, succinate or acetate contain rubredoxin-reductase. By the LAURELL technique we demonstrated that the amount of the enzyme is nearly independent of the carbon source. There are only differences during the different growth phases.     

Metabolism of L(−)-carnitine by Enterobacteriaceae under aerobic conditions

Different Enterobacteriaceae, such as Escherichia coli, Proteus vulgaris and Proteus mirabilis, are able to convert L(-)-carnitine, via crotonobetaine, into gamma-butyrobetaine in the presence of carbon and nitrogen sources under aerobic conditions. Intermediates of L(-)-carnitine metabolism (crotonobetaine, gamma-butyrobetaine) could be detected by thin-layer chromatography. In parallel, L(-)-carnitine dehydratase, carnitine racemasing system and crotonobetaine reductase activities were determined enzymatically. Monoclonal antibodies against purified CaiB and CaiA from E. coli O44K74 were used to screen cell-free extracts of different Enterobacteriaceae (E. coli ATCC 25922, P. vulgaris, P. mirabilis, Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae) grown under aerobic conditions in the presence of L(-)-carnitine.