Biophysical and electrochemical studies of protein-nucleic acid interactions

This review is devoted to biophysical and electrochemical methods used for studying protein-nucleic acid (NA) interactions. The importance of NA structure and protein-NA recognition for essential cellular processes, such as replication or transcription, is discussed to provide background for description of a range of biophysical chemistry methods that are applied to study a wide scope of protein-DNA and protein-RNA complexes. These techniques employ different detection principles with specific advantages and limitations and are often combined as mutually complementary approaches to provide a complete description of the interactions. Electrochemical methods have proven to be of great utility in such studies because they provide sensitive measurements and can be combined with other approaches that facilitate the protein-NA interactions. Recent applications of electrochemical methods in studies of protein-NA interactions are discussed in detail

Generational distribution of a Candida glabrata population: Resilient old cells prevail, while younger cells dominate in the vulnerable host.

Similar to other yeasts, the human pathogen Candida glabrata ages when it undergoes asymmetric, finite cell divisions, which determines its replicative lifespan. We sought to investigate if and how aging changes resilience of C. glabrata populations in the host environment. Our data demonstrate that old C. glabrata are more resistant to hydrogen peroxide and neutrophil killing, whereas young cells adhere better to epithelial cell layers. Consequently, virulence of old compared to younger C. glabrata cells is enhanced in the Galleria mellonella infection model. Electron microscopy images of old C. glabrata cells indicate a marked increase in cell wall thickness. Comparison of transcriptomes of old and young C. glabrata cells reveals differential regulation of ergosterol and Hog pathway associated genes as well as adhesion proteins, and suggests that aging is accompanied by remodeling of the fungal cell wall. Biochemical analysis supports this conclusion as older cells exhibit a qualitatively different lipid composition, leading to the observed increased emergence of fluconazole resistance when grown in the presence of fluconazole selection pressure. Older C. glabrata cells accumulate during murine and human infection, which is statistically unlikely without very strong selection. Therefore, we tested the hypothesis that neutrophils constitute the predominant selection pressure in vivo. When we altered experimentally the selection pressure by antibody-mediated removal of neutrophils, we observed a significantly younger pathogen population in mice. Mathematical modeling confirmed that differential selection of older cells is sufficient to cause the observed demographic shift in the fungal population. Hence our data support the concept that pathogenesis is affected by the generational age distribution of the infecting C. glabrata population in a host. We conclude that replicative aging constitutes an emerging trait, which is selected by the host and may even play an unanticipated role in the transition from a commensal to a pathogen state.post-print10768 K

Drug Resistance in Eukaryotic Microorganisms

Eukaryotic microbial pathogens are major contributors to illness and death globally. Although much of their impact can be controlled by drug therapy as with prokaryotic microorganisms, the emergence of drug resistance has threatened these treatment efforts. Here, we discuss the challenges posed by eukaryotic microbial pathogens and how these are similar to, or differ from, the challenges of prokaryotic antibiotic resistance. The therapies used for several major eukaryotic microorganisms are then detailed, and the mechanisms that they have evolved to overcome these therapies are described. The rapid emergence of resistance and the restricted pipeline of new drug therapies pose considerable risks to global health and are particularly acute in the developing world. Nonetheless, we detail how the integration of new technology, biological understanding, epidemiology and evolutionary analysis can help sustain existing therapies, anticipate the emergence of resistance or optimize the deployment of new therapies

Probiotic lactobacilli inhibit early stages of Candida albicans biofilm development by reducing their growth, cell adhesion, and filamentation

We evaluated the inhibitory effects of the probiotic Lactobacillus species on different phases of Candida albicans biofilm development. Quantification of biofilm growth and ultrastructural analyses were performed on C. albicans biofilms treated with Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus acidophilus planktonic cell suspensions as well as their supernatants. Planktonic lactobacilli induced a significant reduction (p\ua0\ua00.05), but significantly reduced the early stages of Candida biofilm formation (p\ua

Testing of antifungal drugs for the treatment of Candida albicans biofilms using an in vivo subcutaneous rat model system

status: publishe

Different lipid forms of omega-3 and their effect on small intestine in mice

Omega - 3 fatty acids of marine origin exert beneficial effects on lipid metabolism and can protect against insulin resistance in high fat diet (HFD)-fed animals. Simultaneously, recent studies showed that different lipid forms could have numerous consequences regarding the regulation of energy balance, nutrient absorption, and substrate metabolism. Indeed, when omega-3 was provided as triglycerides (TG, i.e. fish oil), it induced dose-dependently the expression of genes involved in lipid metabolism as well as fatty acid oxidation in small intestine of C57BL/6 mice fed various HFDs. As the underlying mechanism(s) explaining the differences in EPA/DHA bioavailability among various lipid forms of Omega-3 is not entirely clear, we performed a mouse study (n=8 per group) using purified HFDs with control HFD based on corn oil (cHF) and part of the lipids were replaced by omega-3 fish lipids in different forms: as either TG (cHF-F), marine phospholipids (PL; Krill oil, given at two different doses Krill-low (Krill-L) and Krill-high (Krill-H)), and as wax esters in the extract from the zooplankton Calanus finmarchicus (Calanus oil CAL-L representing same omega-3 levels as Krill-L diet). As a healthy control we fed a subset of mice standard chow (STD). All mice were fed their diet for 8 weeks and after sacrifice, whole small intestine was isolated, frozen and used for RNA isolation and microarray gene expression analysis using 8x60K Agilent arrays. Results showed that PL-H versus control cHFc induced specifically metabolic lipid pathways, while TG and PL-L mainly affected cytoskeleton regulation

Different lipid forms of omega-3 and their effect on small intestine in mice

Omega - 3 fatty acids of marine origin exert beneficial effects on lipid metabolism and can protect against insulin resistance in high fat diet (HFD)-fed animals. Simultaneously, recent studies showed that different lipid forms could have numerous consequences regarding the regulation of energy balance, nutrient absorption, and substrate metabolism. Indeed, when omega-3 was provided as triglycerides (TG, i.e. fish oil), it induced dose-dependently the expression of genes involved in lipid metabolism as well as fatty acid oxidation in small intestine of C57BL/6 mice fed various HFDs. As the underlying mechanism(s) explaining the differences in EPA/DHA bioavailability among various lipid forms of Omega-3 is not entirely clear, we performed a mouse study (n=8 per group) using purified HFDs with control HFD based on corn oil (cHF) and part of the lipids were replaced by omega-3 fish lipids in different forms: as either TG (cHF-F), marine phospholipids (PL; Krill oil, given at two different doses Krill-low (Krill-L) and Krill-high (Krill-H)), and as wax esters in the extract from the zooplankton Calanus finmarchicus (Calanus oil CAL-L representing same omega-3 levels as Krill-L diet). As a healthy control we fed a subset of mice standard chow (STD). All mice were fed their diet for 8 weeks and after sacrifice, whole small intestine was isolated, frozen and used for RNA isolation and microarray gene expression analysis using 8x60K Agilent arrays. Results showed that PL-H versus control cHFc induced specifically metabolic lipid pathways, while TG and PL-L mainly affected cytoskeleton regulation

Occurrence, antifungal susceptibility, and virulence factors of opportunistic yeasts isolated from Brazilian beaches

BACKGROUND Opportunistic pathogenic yeast species are frequently associated with water habitats that have pollution sources of human or animal origin. Candida albicans has already been suggested as a faecal indicator microorganism for aquatic environments. OBJECTIVES The goal of this study was to investigate the occurrence of C. albicans and other opportunistic yeasts in sand and seawater samples from beaches in Brazil to assess their correlation with Escherichia coli, and to characterise the pathogenic potential of the yeast isolates. METHODS Opportunistic species (yeasts that grow at 37ºC) were isolated from sand and seawater samples from eight beaches in Brazil during the summer and the winter. Opportunistic yeast species were evaluated for their susceptibility to antifungal drugs, virulence factors, and the in vitro and in vivo biofilm formation. Strains were selected to carry out virulence tests using BALB/c mice. FINDINGS Several water samples could be classified as inappropriate for primary contact recreation in relation to E. coli densities. C. albicans was isolated in low densities. Of the 144 opportunistic yeasts evaluated, 61% displayed resistance or dose-dependent sensitivity to at least one tested drug, and 40% produced proteinase. Strains of C. albicans and Kodamaea ohmeri exhibited the highest rates of adhesion to buccal epithelial cells. All the C. albicans strains that were tested were able to undergo morphogenesis and form a biofilm on catheter fragments in both in vitro and in vivo experiments. It was possible to confirm the pathogenic potential of three of these strains during the disseminated infection test. MAIN CONCLUSIONS The identification of opportunistic yeast species in seawater and sand samples from Brazilian beaches suggest a potential risk to the health of people who use these environments for recreational purposes.status: publishe