Bypassing lantibiotic resistance by an effective nisin derivative

The need for new antibiotic compounds is rising and antimicrobial peptides are excellent candidates to fulfill this object. The bacteriocin subgroup lantibiotics, for example, are active in the nanomolar range and target the membranes of mainly Gram-positive bacteria. They bind to lipid II, inhibit cell growth and in some cases form pores within the bacterial membrane, inducing rapid cell death. Pharmaceutical usage of lantibiotics is however hampered by the presence of gene clusters in human pathogenic strains which, when expressed, confer resistance. The human pathogen Streptococcus agalactiae COH1, expresses several lantibiotic resistance proteins resulting in resistance against for example nisin.This study presents a highly potent, pore forming nisin variant as an alternative lantibiotic which bypasses the SaNSR protein. It is shown that this nisin derivate nisin_C28P keeps its nanomolar antibacterial activity against L. lactis NZ9000 cells but is not recognized by the nisin resistance protein SaNSR.Nisin_C28P is cleaved by SaNSR in vitro with a highly decreased efficiency, as shown by an cleavage assay. Furthermore, we show that nisin_C28P is still able to form pores in the membranes of L. lactis and is three times more efficient against SaNSR-expressing L. lactis cells than wildtype nisin.     

Bim, Bad and Bmf: intrinsically unstructured BH3-only proteins that undergo a localized conformational change upon binding to prosurvival Bcl-2 targets

All BH3-only proteins, key initiators of programmed cell death, interact tightly with multiple binding partners and have sequences of low complexity, properties that are the hallmark of intrinsically unstructured proteins (IUPs). We show, using spectroscopic methods, that the BH3-only proteins Bim, Bad and Bmf are unstructured in the absence of binding partners. Detailed sequence analyses are consistent with this observation and suggest that most BH3-only proteins are unstructured. When Bim binds and inactivates prosurvival proteins, most residues remain disordered, only the BH3 element becomes structured, and the short alpha-helical molecular recognition element can be considered to behave as a 'bead on a string'. Coupled folding and binding is typical of many IUPs that have important signaling roles, such as BH3-only proteins, as the inherent structural plasticity favors interaction with multiple targets. This understanding offers promise for the development of BH3 mimetics, as multiple modes of binding are tolerated.     

Fasting protects against the side effects of irinotecan but preserves its anti-tumor effect in Apc15lox mutant mice

Irinotecan is a widely used topoisomerase-I-inhibitor with a very narrow therapeutic window because of its severe toxicity. In the current study we have examined the effects of fasting prior to irinotecan treatment on toxicity and anti-tumor activity. FabplCre;Apc^15lox/+ mice, which spontaneously develop intestinal tumors, of 27 weeks of age were randomized into 3-day fasted and ad libitum fed groups, followed by treatment with a flat-fixed high dose of irinotecan or vehicle. Side-effects were recorded until 11 days after the start of the experiment. Tumor size, and markers for cell-cycle activity, proliferation, angiogenesis, and senescence were measured. Fasted mice were protected against the side-effects of irinotecan treatment. Ad libitum fed mice developed visible signs of discomfort including weight loss, lower activity, ruffled coat, hunched-back posture, diarrhea, and leukopenia. Irinotecan reduced tumor size in fasted and ad libitum fed groups similarly compared to untreated controls (2.4 ± 0.67 mm and 2.4 ± 0.82 mm versus 3.0 ± 1.05 mm and 2.8 ± 1.08 mm respectively, P < 0.001). Immunohistochemical analysis showed reduced proliferation, a reduced number of vascular endothelial cells, and increased levels of senescence in tumors of both irinotecan treated groups. In conclusion, 3 days of fasting protects against the toxic side-effects of irinotecan in a clinically relevant mouse model of spontaneously developing colorectal cancer without affecting its anti-tumor activity. These results support fasting as a powerful way to improve treatment of colorectal carcinoma patients.     

Appropriate use of bioresorbable vascular scaffolds in percutaneous coronary interventions: a recommendation from experienced users: A position statement on the use of bioresorbable vascular scaffolds in the Netherlands

Percutaneous coronary interventions (PCI) have become a reliable revascularisation option to treat ischaemic coronary artery disease. Drug-eluting stents (DES) are widely used as first choice devices in many procedures due to their established good medium to long term outcomes. These permanent implants, however, do not have any residual function after vascular healing following the PCI. Beyond this initial healing period, metallic stents may induce new problems, resulting in an average rate of 2 % reinterventions per year. To eliminate this potential late limitation of permanent metallic DES, bioresorbable coronary stents or ‘vascular scaffolds’ (BVS) have been developed. In a parallel publication in this journal, an overview of the current clinical performance of these scaffolds is presented. As these scaffolds are currently CE marked and commercially available in many countries and as clinical evidence is still limited, recommendations for their general usage are needed to allow successful clinical introduction.     

Genome sequence of Fibrella aestuarina BUZ 2(T), a filamentous marine bacterium

Fibrella aestuarina BUZ 2(T) is the type strain of the recently characterized genus Fibrella. Here we report the draft genome sequence of this strain, which consists of a single scaffold representing the chromosome (with 11 gaps) and a 161-kb circular plasmid.     

Chromosomal replication initiation machinery of low-g+c-content firmicutes

Much of our knowledge of the initiation of DNA replication comes from studies in the Gram-negative model organism Escherichia coli. However, the location and structure of the origin of replication within the E. coli genome and the identification and study of the proteins which constitute the E. coli initiation complex suggest that it might not be as universal as once thought. The archetypal low-G+C-content Gram-positive Firmicutes initiate DNA replication via a unique primosomal machinery, quite distinct from that seen in E. coli, and an examination of oriC in the Firmicutes species Bacillus subtilis indicates that it might provide a better model for the ancestral bacterial origin of replication. Therefore, the study of replication initiation in organisms other than E. coli, such as B. subtilis, will greatly advance our knowledge and understanding of these processes as a whole. In this minireview, we highlight the structure-function relationships of the Firmicutes primosomal proteins, discuss the significance of their oriC architecture, and present a model for replication initiation at oriC.     

Quantitative Analysis of the Modes of Growth Inhibition by Weak Organic Acids in Saccharomyces cerevisiae

Weak organic acids are naturally occurring compounds that are commercially used as preservatives in the food and beverage industries. They extend the shelf life of food products by inhibiting microbial growth. There are a number of theories that explain the antifungal properties of these weak acids, but the exact mechanism is still unknown. We set out to quantitatively determine the contributions of various mechanisms of antifungal activity of these weak acids, as well as the mechanisms that yeast uses to counteract their effects. We analyzed the effects of four weak organic acids differing in lipophilicity (sorbic, benzoic, propionic, and acetic acids) on growth and intracellular pH (pH_i) in Saccharomyces cerevisiae. Although lipophilicity of the acids correlated with the rate of acidification of the cytosol, our data confirmed that not initial acidification, but rather the cell''s ability to restore pH_i, was a determinant for growth inhibition. This pH_i recovery in turn depended on the nature of the organic anion. We identified long-term acidification as the major cause of growth inhibition under acetic acid stress. Restoration of pH_i, and consequently growth rate, in the presence of this weak acid required the full activity of the plasma membrane ATPase Pma1p. Surprisingly, the proposed anion export pump Pdr12p was shown to play an important role in the ability of yeast cells to restore the pH_i upon lipophilic (sorbic and benzoic) acid stress, probably through a charge interaction of anion and proton transport.     

Living Rivers: Trends and Challenges in Science and Management

This paper discusses and summarizes the major conclusions of the special issue entitled ‘Living rivers: trends and challenges in science and management’ of Hydrobiologia/Developments in Hydrobiology. It is structured along three lines: (1) Functioning of river systems; (2) Ecological rehabilitation of river systems; (3) Challenges and obstacles to sustainable management. Sustainable river basin management requires a thorough understanding of natural, physical, chemical and ecological processes as well as socio-economic functioning. Environmental rehabilitation of river systems inevitably requires an ecosystem-based approach involving solutions supported by the public. The challenge is to combine ecological and socio-economic sustainability. Rethinking our efforts in both directions must lead to more innovative solutions than those available at present.     

Polo-like kinase-1 controls proteasome-dependent degradation of Claspin during checkpoint recovery

DNA-damage checkpoints maintain genomic integrity by mediating a cell-cycle delay in response to genotoxic stress or stalled replication forks. In response to damage, the checkpoint kinase ATR phosphorylates and activates its effector kinase Chk1 in a process that critically depends on Claspin . However, it is not known how exactly this kinase cascade is silenced. Here we demonstrate that the abundance of Claspin is regulated through proteasomal degradation. In response to DNA damage, Claspin is transiently stabilized, and its expression depends on Chk1 kinase activity. In addition, we show that Claspin is degraded upon mitotic entry, a process that depends on the beta-TrCP-SCF ubiquitin ligase and Polo-like kinase-1 (Plk1). We demonstrate that Claspin interacts with both beta-TrCP and Plk1 and that inactivation of these components or the beta-TrCP recognition motif in Claspin prevents its mitotic degradation. Interestingly, expression of a nondegradable Claspin mutant inhibits recovery from a DNA-damage-induced checkpoint arrest. Thus, we conclude that Claspin levels are tightly regulated, both during unperturbed cell cycles and after DNA damage. Moreover, our data demonstrate that the degradation of Claspin at the onset of mitosis is an essential step for the recovery of a cell from a DNA-damage-induced cell-cycle arrest.