Spore cortex formation in Bacillus subtilis is regulated by accumulation of peptidoglycan precursors under the control of sigma K

The bacterial endospore cortex peptidoglycan is synthesized between the double membranes of the developing forespore and is required for attainment of spore dehydration and dormancy. The Bacillus subtilis spoVB, spoVD and spoVE gene products are expressed in the mother cell compartment early during sporulation and play roles in cortex synthesis. Here we show that mutations in these genes block synthesis of cortex peptidoglycan and cause accumulation of peptidoglycan precursors, indicating a defect at the earliest steps of peptidoglycan polymerization. Loss of spoIV gene products involved in activation of later, sigma(K)-dependent mother cell gene expression results in decreased synthesis of cortex peptidoglycan, even in the presence of the SpoV proteins that were synthesized earlier, apparently due to decreased precursor production. Data show that activation of sigma(K) is required for increased synthesis of the soluble peptidoglycan precursors, and Western blot analyses show that increases in the precursor synthesis enzymes MurAA, MurB, MurC and MurF are dependent on sigma(K) activation. Overall, our results indicate that a decrease in peptidoglycan precursor synthesis during early sporulation, followed by renewed precursor synthesis upon sigma(K) activation, serves as a regulatory mechanism for the timing of spore cortex synthesis.     

Loss of cell wall alpha(1-3) glucan affects Cryptococcus neoformans from ultrastructure to virulence

Yeast cell walls are critical for maintaining cell integrity, particularly in the face of challenges such as growth in mammalian hosts. The pathogenic fungus Cryptococcus neoformans additionally anchors its polysaccharide capsule to the cell surface via alpha(1-3) glucan in the wall. Cryptococcal cells disrupted in their alpha glucan synthase gene were sensitive to stresses, including temperature, and showed difficulty dividing. These cells lacked surface capsule, although they continued to shed capsule material into the environment. Electron microscopy showed that the alpha glucan that is usually localized to the outer portion of the cell wall was absent, the outer region of the wall was highly disorganized, and the inner region was hypertrophic. Analysis of cell wall composition demonstrated complete loss of alpha glucan accompanied by a compensatory increase in chitin/chitosan and a redistribution of beta glucan between cell wall fractions. The mutants were unable to grow ina mouse model of infection, but caused death in nematodes. These studies integrate morphological and biochemical investigations of the role of alpha glucan in the cryptococcal cell wall.     

What is the Value of a Good Map? An Example Using High Spatial Resolution Imagery to Aid Riparian Restoration

Riparian areas contain structurally diverse habitats that are challenging to monitor routinely and accurately over broad areas. As the structural variability within riparian areas is often indiscernible using moderate-scale satellite imagery, new mapping techniques are needed. We used high spatial resolution satellite imagery from the QuickBird satellite to map harvested and intact forests in coastal British Columbia, Canada. We distinguished forest structural classes used in riparian restoration planning, each with different restoration costs. To assess the accuracy of high spatial resolution imagery relative to coarser imagery, we coarsened the pixel resolution of the image, repeated the classifications, and compared results. Accuracy assessments produced individual class accuracies ranging from 70 to 90% for most classes; whilst accuracies obtained using coarser scale imagery were lower. We also examined the implications of map error on riparian restoration budgets derived from our classified maps. To do so, we modified the confusion matrix to create a cost error matrix quantifying costs associated with misclassification. High spatial resolution satellite imagery can be useful for riparian mapping; however, errors in restoration budgets attributable to misclassification error can be significant, even when using highly accurate maps. As the spatial resolution of imagery increases, it will be used more routinely in ecosystem ecology. Thus, our ability to evaluate map accuracy in practical, meaningful ways must develop further. The cost error matrix is one method that can be adapted for conservation and planning decisions in many ecosystems.     

Novel hopanoid cyclases from the environment

Hopanoids are ubiquitous isoprenoid lipids found in modern biota, in recent sediments and in low-maturity sedimentary rocks. Because these lipids primarily are derived from bacteria, they are used as proxies to help decipher geobiological communities. To date, much of the information about sources of hopanoids has come from surveys of culture collections, an approach that does not address the vast fraction of prokaryotic communities that remains uncharacterized. Here we investigated the phylogeny of hopanoid producers using culture-independent methods. We obtained 79 new sequences of squalene-hopene cyclase genes (sqhC) from marine and lacustrine bacterioplankton and analysed them along with all 31 sqhC fragments available from existing metagenomics libraries. The environmental sqhCs average only 60% translated amino acid identity to their closest relatives in public databases. The data imply that the sources of these important geologic biomarkers remain largely unknown. In particular, genes affiliated with known cyanobacterial sequences were not detected in the contemporary environments analysed here, yet the geologic record contains abundant hopanoids apparently of cyanobacterial origin. The data also suggest that hopanoid biosynthesis is uncommon: < 10% of bacterial species may be capable of producing hopanoids. A better understanding of the contemporary distribution of hopanoid biosynthesis may reveal fundamental insight about the function of these compounds, the organisms in which they are found, and the environmental signals preserved in the sedimentary record.     

Highly purified lipopolysaccharides from Burkholderia cepacia complex clinical isolates induce inflammatory cytokine responses via TLR4-mediated MAPK signalling pathways and activation of NFkappaB

In cystic fibrosis (CF), bacteria of the Burkholderia cepacia complex (Bcc) can induce a fulminant inflammation with pneumonitis and sepsis. Lipopolysaccharide (LPS) may be an important virulence factor associated with this decline but little is known about the molecular pathogenesis of Bcc LPS. In this study we have investigated the inflammatory response to highly purified LPS from different Bcc clinical isolates and the cellular signalling pathways employed. The inflammatory response (TNFalpha, IL-6) was measured in human MonoMac 6 monocytes and inhibition experiments were used to investigate the Toll-like receptors and associated adaptor molecules and pathways utilized. LPS from all clinical Bcc isolates induced significant pro-inflammatory cytokines and utilized TLR4 and CD14 to mediate activation of mitogen-activated protein kinase pathways, IkappaB-alpha degradation and NFkappaB activation. However, LPS from different clinical isolates of the same clonal strain of Burkholderia cenocepacia were found to induce a varied inflammatory response. LPS from clinical isolates of Burkholderia multivorans was found to activate the inflammatory response via MyD88-independent pathways. This study suggests that LPS alone from clinical isolates of Bcc is an important virulence factor in CF and utilizes TLR4-mediated signalling pathways to induce a significant inflammatory response.     

The folding and evolution of multidomain proteins

Analyses of genomes show that more than 70% of eukaryotic proteins are composed of multiple domains. However, most studies of protein folding focus on individual domains and do not consider how interactions between domains might affect folding. Here, we address this by analysing the three-dimensional structures of multidomain proteins that have been characterized experimentally and observe that where the interface is small and loosely packed, or unstructured, the folding of the domains is independent. Furthermore, recent studies indicate that multidomain proteins have evolved mechanisms to minimize the problems of interdomain misfolding.     

Translational principles of deep brain stimulation

Deep brain stimulation (DBS) has shown remarkable therapeutic benefits for patients with otherwise treatment-resistant movement and affective disorders. This technique is not only clinically useful, but it can also provide new insights into fundamental brain functions through direct manipulation of both local and distributed brain networks in many different species. In particular, DBS can be used in conjunction with non-invasive neuroimaging methods such as magnetoencephalography to map the fundamental mechanisms of normal and abnormal oscillatory synchronization that underlie human brain function. The precise mechanisms of action for DBS remain uncertain, but here we give an up-to-date overview of the principles of DBS, its neural mechanisms and its potential future applications.     

A genetic association analysis of cognitive ability and cognitive ageing using 325 markers for 109 genes associated with oxidative stress or cognition

Background

Non-pathological cognitive ageing is a distressing condition affecting an increasing number of people in our 'ageing society'. Oxidative stress is hypothesised to have a major role in cellular ageing, including brain ageing.

Results

Associations between cognitive ageing and 325 single nucleotide polymorphisms (SNPs), located in 109 genes implicated in oxidative stress and/or cognition, were examined in a unique cohort of relatively healthy older people, on whom we have cognitive ability scores at ages 11 and 79 years (LBC1921). SNPs showing a significant positive association were then genotyped in a second cohort for whom we have cognitive ability scores at the ages of 11 and 64 years (ABC1936). An intronic SNP in the APP gene (rs2830102) was significantly associated with cognitive ageing in both LBC1921 and a combined LBC1921/ABC1936 analysis (p < 0.01), but not in ABC1936 alone.

Conclusion

This study suggests a possible role for APP in normal cognitive ageing, in addition to its role in Alzheimer's disease.