Evidence for the presence of the glyoxylate cycle in Chloroflexus

The key enzymes of the glyoxylate cycle, isocitrate lyase and malate synthase, were present in cell-free extracts of the phototrophic, green, thermophilic bacterium Chloroflexus aurantiacus grown with acetate as the sole organic carbon source.The optimum temperature of these enzymes was 40° C, and their specific activities were high enough to account for the observed growth rate. Lower levels of the enzymes were found in extracts from cells grown on a complete medium.Itaconate was shown to inhibit isocitrate lyase from C. aurantiacus 96% at a concentration of 0.25 mM and also had a profound effect on the growth of the organism on acetate, 0.25 mM inhibiting completely. Itaconate also inhibited the growth when added to the complex medium, but in this case much higher concentrations were required.     

Primula farinosa in Denmark; genetic diversity and population management

During the past centuries Danish populations of Primula farinosa have seriously declined in number. We investigated the genetic structure and genetic diversity of plants of seven populations from two different regions, Zealand and Bornholm in Denmark, using three AFLP markers. Two populations from nearby Scania, Sweden were included as reference. We found 54 unambiguously polymorphic loci. The genetic structure analysis suggested division of the 268 plants into three distinct groups, to a large extent matching the geographical distribution of the populations. Analysis of molecular variance (AMOVA) indicated significant genetic differentiation of 67% within populations and 33% among the populations. Our results suggest that genetic differentiation among regions and unique local genetic diversity should carefully be considered in future conservation attempts if we are to maintain as much genetic variation as possible. We present a historical overview of the decline in Danish populations and discuss conservation management and restoration strategies.     

Removal of acidic residues of the prodomain of PCSK9 increases its activity towards the LDL receptor

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the low density lipoprotein receptor (LDLR) at the cell surface and mediates intracellular degradation of the LDLR. The amino-terminus of mature PCSK9, residues 31–53 of the prodomain, has an inhibitory effect on this function of PCSK9, but the underlying mechanism is not fully understood. In this study, we have identified two highly conserved negatively charged segments (residues 32–40 and 48–50, respectively) within this part of the prodomain and performed deletions and substitutions to study their importance for degradation of the LDLRs.Deletion of the acidic residues of the longest negatively charged segment increased PCSK9’s ability to degrade the LDLR by 31%, whereas a modest 8% increase was observed when these residues were mutated to uncharged amino acids. Thus, both the length and the charge of this part of the prodomain were important for its inhibitory effect. Deletion of the residues of the shorter second negatively charged segment only increased PCSK9’s activity by 8%. Substitution of the amino acids of both charged segments to uncharged residues increased PCSK9’s activity by 36%. These findings indicate that the inhibitory effect of residues 31–53 of the prodomain is due to the negative charge of this segment. The underlying mechanism could involve the binding of this peptide segment to positively charged structures which are important for PCSK9’s activity. One possible candidate could be the histidine-rich C-terminal domain of PCSK9.     

Comparative multilocus phylogeography of two Palaearctic spruce bark beetles: influence of contrasting ecological strategies on genetic variation

While phylogeographic patterns of organisms are often interpreted through past environmental disturbances, mediated by climate changes, and geographic barriers, they may also be strongly influenced by species‐specific traits. To investigate the impact of such traits, we focused on two Eurasian spruce bark beetles that share a similar geographic distribution, but differ in their ecology and reproduction. Ips typographus is an aggressive tree‐killing species characterized by strong dispersal, whereas Dendroctonus micans is a discrete inbreeding species (sib mating is the rule), parasite of living trees and a poor disperser. We compared genetic variation between the two species over both beetles’ entire range in Eurasia with five independent gene fragments, to evaluate whether their intrinsic differences could have an influence over their phylogeographic patterns. We highlighted widely divergent patterns of genetic variation for the two species and argue that the difference is indeed largely compatible with their contrasting dispersal strategies and modes of reproduction. In addition, genetic structure in I. typographus divides European populations in a northern and a southern group, as was previously observed for its host plant, and suggests past allopatric divergence. A long divergence time was estimated between East Asian and other populations of both species, indicating their long‐standing presence in Eurasia, prior to the last glacial maximum. Finally, the strong population structure observed in D. micans for the mitochondrial locus provides insights into the recent colonization history of this species, from its native European range to regions where it was recently introduced.     

Extrapair paternity and genetic diversity: the white‐throated dipper Cinclus cinclus

Passerine bird species vary considerably in the frequency of extrapair paternity, but the factors causing this variation are not well understood. There is some comparative evidence that extrapair paternity is associated with the population level of genetic diversity, but there is no consensus of how genetic diversity should be measured and compared across species or populations. Here we report a low frequency of extrapair paternity (2% extrapair offspring) in a Norwegian population of the white‐throated dipper Cinclus cinclus, which shows strong signs of reduced genetic diversity. We encountered difficulties in constructing a robust parentage analysis system for the species, largely due to consistently low polymorphism levels in 100 heterologous microsatellite markers. Furthermore, single‐nucleotide polymorphisms (SNPs) were almost absent in intron sequences in 10 nuclear genes (>5 kb) that are much more polymorphic in other species. Hence, our results seem consistent with the genetic diversity hypothesis that predicts a low frequency of extrapair paternity in species with low genetic diversity. Heterologous microsatellite markers are generally unsuitable for interspecific comparisons of genetic diversity as they show strong phylogenetic dependency in polymorphism levels. We suggest that SNP rates at homologous nuclear introns, like those presented here, can provide a useful method for obtaining unbiased estimates of genome‐wide genetic diversity across populations and species.     

Propionibacterium jensenii produces the polyene pigment granadaene and has hemolytic properties similar to those of Streptococcus agalactiae

The red polyene pigment granadaene was purified and identified from Propionibacterium jensenii. Granadaene has previously been identified only in Streptococcus agalactiae, where the pigment correlates with the hemolytic activity of the bacterium. A connection between hemolytic activity and the production of the red pigment has also been observed in P. jensenii, as nonpigmented strains are nonhemolytic. The pigment and hemolytic activity from S. agalactiae can be extracted from the bacterium with a starch extraction solution, and this solution also extracts the pigment and hemolytic activity from P. jensenii. A partial purification of the hemolytic activity was achieved, but the requirement for starch to preserve its activity made the purification unsuccessful. Partially purified hemolytic fractions were pigmented, and the color intensity of the fractions coincided with the hemolytic titer. The pigment was produced in a soluble form when associated with starch, and the UV-visual spectrum of the extract gave absorption peaks of 463 nm, 492 nm, and 524 nm. The pigment could also be extracted from the cells by a low-salt buffer, but it was then aggregated. The purification of the pigment from P. jensenii was performed, and mass spectrometry and nuclear magnetic resonance analysis revealed that P. jensenii indeed produces granadaene as seen in S. agalactiae.     

From symbolism to information? – Decoding the gene code

‘Information’ and ‘code’ originated as technical terms within linguistics and information theory but are now widely used in genetics and developmental biology. Against this background, it is examined if coded information distinguishes genes from other information carriers, i.e., whether there are genetic words or sentences by virtue of the genetic code, and, if so, whether they have any semantic content. It is concluded that there is no genetic language with semantic content, but that the genetic code still enables unique language-like modes of transmission and interpretation of causal information.     

Agonistic anti-CD40 antibody profoundly suppresses the immune response to infection with lymphocytic choriomeningitis virus

Previous work has shown that agonistic Abs to CD40 (anti-CD40) can boost weak CD8 T cell responses as well as substitute for CD4 T cell function during chronic gammaherpes virus infection. Agonistic anti-CD40 treatment has, therefore, been suggested as a potential therapeutic strategy in immunocompromised patients. In this study, we investigated whether agonistic anti-CD40 could substitute for CD4 T cell help in generating a sustained CD8 T cell response and prevent viral recrudescence following infection with lymphocytic choriomeningitis virus (LCMV). Contrary to expectations, we found that anti-CD40 treatment of MHC class II-deficient mice infected with a moderate dose of LCMV resulted in severe suppression of the antiviral CD8 T cell response and uncontrolled virus spread, rather than improved CD8 T cell immune surveillance. In Ab-treated wild-type mice, the antiviral CD8 T cell response also collapsed prematurely, and virus clearance was delayed. Additional analysis revealed that, following anti-CD40 treatment, the virus-specific CD8 T cells initially proliferated normally, but an increased cell loss compared with that in untreated mice was observed. The anti-CD40-induced abortion of virus-specific CD8 T cells during LCMV infection was IL-12 independent, but depended partly on Fas expression. Notably, similar anti-CD40 treatment of vesicular stomatitis virus-infected mice resulted in an improved antiviral CD8 T cell response, demonstrating that the effect of anti-CD40 treatment varies with the virus infection studied. For this reason, we recommend further evaluation of the safety of this regimen before being applied to human patients.     

Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.     

Single cell studies and simulation of cell-cell interactions using oscillating glycolysis in yeast cells

The observation of oscillations in the concentrations of NADH and other intermediates in glycolysis in dense yeast cell suspensions is generally believed to be the result of synchronization of such oscillations between individual cells. The synchrony is believed to be a property of cell density and the question is: does metabolism in each individual yeast cell continue to oscillate, but out of phase, in the absence of synchronization? Here we have used high-sensitivity fluorescence microscopy to measure NADH in single isolated yeast cells under conditions where we observe oscillations of glycolysis in dense cell suspensions. However, we have not been able to detect intracellular oscillations in NADH in these isolated cells, which cannot synchronize their metabolism with other cells. However, addition of acetaldehyde to a single cell as pulses with a frequency similar to the oscillations in dense cell suspensions will induce oscillations in that cell. Ethanol, another product of glycolysis, which has been proposed as a synchronizing agent of glycolysis in cells, was not able to induce oscillations when added as pulses. The experiments support the notion that the intracellular oscillations are associated with the cell density of the yeast cell suspension and mediated by acetaldehyde and perhaps also other substances.