Customized media based on miniaturized screening improve growth rate and cell yield of methane-oxidizing bacteria of the genus Methylomonas

The growth of twelve methanotrophic strains within the genus Methylomonas, including the type strains of Methylomonas methanica and Methylomonas koyamae, was evaluated with 40 different variations of standard diluted nitrate mineral salts medium in 96-well microtiter plates. Unique profiles of growth preference were observed for each strain, showing a strong strain dependency for optimal growth conditions, especially with regards to the preferred concentration and nature of the nitrogen source. Based on the miniaturized screening results, a customized medium was designed for each strain, allowing the improvement of the growth of several strains in a batch setup, either by a reduction of the lag phase or by faster biomass accumulation. As such, the maintenance of fastidious strains could be facilitated while the growth of fast-growing Methylomonas strains could be further improved. Methylomonas sp. R-45378 displayed a 50 % increase in cell dry weight when grown in its customized medium and showed the lowest observed nitrogen and oxygen requirement of all tested strains. We demonstrate that the presented miniaturized approach for medium optimization is a simple tool allowing the quick generation of strain-specific growth preference data that can be applied downstream of an isolation campaign. This approach can also be applied as a first step in the search for strains with biotechnological potential, to facilitate cultivation of fastidious strains or to steer future isolation campaigns.     

The insect upper lip (labrum) is a nonsegmental appendage-like structure

SUMMARY The insect upper lip—the labrum—is a lobe-like structure anterior to the mouth opening. Whether the labrum represents a fused pair of segmental appendages or evolved independently is heavily debated. Here, we identify additional similarities of the regulatory gene network active in labrum and trunk appendages. However, we do not find a labral parasegment boundary and we show that labral Tc-Dll expression is independent of Tc-wg and Tc-hh signals. In contrast, Tc-Dll expression in all trunk appendages does require these signals. Finally, we identify crucial differences between the location of the labrum and trunk appendages: the labrum develops in median rather than lateral tissues and is part of an anterior nonsegmental tissue marked by and dependent on Tc-six3 activity. To reconcile these seeming contradictory results, we propose that the genetic network evolved in either labrum or trunk appendages and became redeployed at a novel location to form the other structure.     

Fairy wrasses perceive and respond to their deep red fluorescent coloration

Fluorescence enables the display of wavelengths that are absent in the natural environment, offering the potential to generate conspicuous colour contrasts. The marine fairy wrasse Cirrhilabrus solorensis displays prominent fluorescence in the deep red range (650–700 nm). This is remarkable because marine fishes are generally assumed to have poor sensitivity in this part of the visual spectrum. Here, we investigated whether C. solorensis males can perceive the fluorescence featured in this species by testing whether the presence or absence of red fluorescence affects male–male interactions under exclusive blue illumination. Given that males respond aggressively towards mirror-image stimuli, we quantified agonistic behaviour against mirrors covered with filters that did or did not absorb long (i.e. red) wavelengths. Males showed significantly fewer agonistic responses when their fluorescent signal was masked, independent of brightness differences. Our results unequivocally show that C. solorensis can see its deep red fluorescent coloration and that this pattern affects male–male interactions. This is the first study to demonstrate that deep red fluorescent body coloration can be perceived and has behavioural significance in a reef fish.     

Life strategies, dominance patterns and mechanisms promoting species coexistence in phytoplankton communities along complex environmental gradients

This paper analyses the life strategies, the dominance patterns and the diversity in phytoplankton communities in large and deep lakes. The study was carried out on the largest Italian Lake (Lake Garda) from 1995 to 2000. Different statistical analyses were applied. For phytoplankton the time variable represents a complex environmental gradient driving annual succession; this gradient was made explicit by the application of PCA analyses to the environmental data. The use of Non Metric Multi Dimensional Scaling applied to Bray-Curtis dissimilarity matrices revealed an ordered and cyclic development of phytoplankton every year; the Bray-Curtis index, calculated between pairs of chronologically contiguous samples, was also used as a measure of the community change rate (β_t) over the temporal succession. A significant relationship between β_t and the complex environmental gradient was assessed. Finally, for every phytoplankton species, the optimum conditions for growth and the realised niches were determined. The positioning of the species on the complex environmental gradient, and the contemporaneous application of cluster analysis based on the different specific environmental optima, highlighted primarily the existence of two groups at the extreme of the complex environmental gradient. The first group included the large late winter/spring diatoms, which developed during high water turbulence and strong physical control, high nutrient concentrations, low light conditions and reduced competition. The second group was composed by many heterogeneous summer species characterised by the ability to contrast losses by grazing and sinking in stratified and stable conditions, and the ability of tolerating nutrient deficiency. A third group of species developed during environmental conditions in the middle of the two previous extremes. These included the three master species Mougeotia sp., Fragilaria crotonensis and Planktothrix rubescens/agardhii. The endogenous and exogenous mechanisms promoting species coexistence are discussed, along with the applicability of competitive and equilibrium/non-equilibrium theories to phytoplankton dynamics.     

Quality control of Utermöhl-based phytoplankton counting and biovolume estimates—an easy task or a Gordian knot?

The most suitable way for standardizing biovolume based assemblage analysis using the Utermöhl technique for counting combined with biomass conversion has not yet been found even though this method has been successfully used in plankton studies for many years. Due to the complexity of the approach easily applicable steps to initially meet primary standard end point or target counts for intra-laboratory standardization tested here seem promising. Examples from count validation and biometric data from the large datasets of three laboratories are given. The first two examples initially intended to quantify the taxon specific scatter of counts by (A) using identical replica of field samples combined with a half-chamber count (scan of every second transect) and the 30 random field approach, respectively, and (B) the replication of transect counts in one sample. Both examples identified relatively low minimum count thresholds to delimit counting errors for single cell counts. The third example identifies shape variability and allometric relationships of the main axes and shows a way to improve taxon specific biomass estimates with special reference to cell thickness. However improved precision of quantitative phytoplankton analysis requires optimization of combined counting strategy and biovolume assessment methods.     

Early Effects of Reward Anticipation Are Modulated by Dopaminergic Stimulation

The abilities to predict future rewards and assess the value of reward delivery are crucial aspects of adaptive behavior. While the mesolimbic system, including dopaminergic midbrain, ventral striatum and prefrontal cortex have long been associated with reward processing, recent studies also indicate a prominent role of early visual brain regions. However, the precise underlying neural mechanisms still remain unclear. To address this issue, we presented participants with visual cues predicting rewards of high and low magnitudes and probability (2×2 factorial design), while neural activity was scanned using magnetoencephalography. Importantly, one group of participants received 150 mg of the dopamine precursor levodopa prior to the experiment, while another group received a placebo. For the placebo group, neural signals of reward probability (but not magnitude) emerged at ∼100 ms after cue presentation at occipital sensors in the event-related magnetic fields. Importantly, these probability signals were absent in the levodopa group indicating a close link. Moreover, levodopa administration reduced oscillatory power in the high (20–30 Hz) and low (13–20 Hz) beta band during both reward anticipation and delivery. Taken together, our findings indicate that visual brain regions are involved in coding prospective reward probability but not magnitude and that these effects are modulated by dopamine.     

Full Inactivation of Human Influenza Virus by High Hydrostatic Pressure Preserves Virus Structure and Membrane Fusion While Conferring Protection to Mice against Infection

Whole inactivated vaccines (WIVs) possess greater immunogenicity than split or subunit vaccines, and recent studies have demonstrated that WIVs with preserved fusogenic activity are more protective than non-fusogenic WIVs. In this work, we describe the inactivation of human influenza virus X-31 by high hydrostatic pressure (HHP) and analyze the effects on the structure by spectroscopic measurements, light scattering, and electron microscopy. We also investigated the effects of HHP on the glycoprotein activity and fusogenic activity of the viral particles. The electron microscopy data showed pore formation on the viral envelope, but the general morphology was preserved, and small variations were seen in the particle structure. The activity of hemagglutinin (HA) during the process of binding and fusion was affected in a time-dependent manner, but neuraminidase (NA) activity was not affected. Infectious activity ceased after 3 hours of pressurization, and mice were protected from infection after being vaccinated. Our results revealed full viral inactivation with overall preservation of viral structure and maintenance of fusogenic activity, thereby conferring protection against infection. A strong response consisting of serum immunoglobulin IgG1, IgG2a, and serum and mucosal IgA was also detected after vaccination. Thus, our data strongly suggest that applying hydrostatic pressure may be an effective method for developing new vaccines against influenza A as well as other viruses.