Serratia marcescens forms a new type of cytolysin

Most Serratia marcescens strains produce a new type of cytolysin (hemolysin) which is also found in other Serratia species. The hemolytic polypeptide ShlA (M(r) 162 101) is secreted across the outer membrane through the help of the ShlB protein which also involves conversion of an inactive precursor in an hemolytically active form. Both proteins are synthesized with signal sequences which are released during export across the cytoplasmic membrane. Mutants expressing inactive ShlB derivatives are impaired in activation and secretion suggesting a tight coupling between both processes. The region of ShlA for activation and secretion is confined to the N-terminal 16% of the polypeptide which contains the sequence NPNG which is also found in the Proteus hemolysin, the Bordetella pertussis filamentous hemagglutinin and two highly expressed outer membrane proteins of Haemophilus influenzae. Substitution of the first asparagine (N) residue by isoleucine converts the Serratia hemolysin into an inactive secretion incompetent form. It is concluded that this region is recognized by ShlB for activation and secretion of ShlA. The Serratia hemolysin forms defined pores in erythrocyte membranes.     

Methods Involving Light Variation for Isolation of Cyanobacteria: Characterization of Isolates from Central Australia

We report the isolation of organisms belonging to a range of cyanobacterial genera from the remote arid region of central Australia, together with a preliminary characterization of their temporal modes of nitrogen fixation. We rendered unialgal Dermocarpa and Myxosarcina spp. (Section II organisms), LPP group B: type X (Section III), and Scytonema and Nostoc spp. (Section IV). We developed an isolation procedure based on a combination of published methods and applicable to a broad spectrum of cyanobacterial genera. We found light intensity to be a critical variable in our methodology; it was also an important determinant of the proportions of different organisms growing in stable mixtures.     

The calcium-dependent ribonuclease XendoU promotes ER network formation through local RNA degradation

How cells shape and remodel organelles in response to cellular signals is a poorly understood process. Using Xenopus laevis egg extract, we found that increases in cytosolic calcium lead to the activation of an endogenous ribonuclease, XendoU. A fraction of XendoU localizes to the endoplasmic reticulum (ER) and is required for nuclear envelope assembly and ER network formation in a catalysis-dependent manner. Using a purified vesicle fusion assay, we show that XendoU functions on the surface of ER membranes to promote RNA cleavage and ribonucleoprotein (RNP) removal. Additionally, RNA removal from the surface of vesicles by RNase treatment leads to increased ER network formation. Using human tissue culture cells, we found that hEndoU localizes to the ER, where it promotes the formation of ER tubules in a catalysis-dependent manner. Together, these results demonstrate that calcium-activated removal of RNA from membranes by XendoU promotes and refines ER remodeling and the formation of tubular ER.     

Conservation strategies for lichens: insights from population biology

To design effective conservation strategies, the population biology of the target organism needs to be well understood. In lichens, the population dynamics of the symbiotic organism is closely tied to the dynamics of its substrate. Here, we review the population biology of selected lichens, highlighting the link between landscape and lichen population dynamics. We suggest strategies to efficiently protect lichen species and develop priorities for species conservation approaches.     

Endogenous tissue engineering: PTH therapy for skeletal repair

Based on its proven anabolic effects on bone in osteoporosis patients, recombinant parathyroid hormone (PTH_1-34) has been evaluated as a potential therapy for skeletal repair. In animals, the effect of PTH_1-34 has been investigated in various skeletal repair models such as fractures, allografting, spinal arthrodesis and distraction osteogenesis. These studies have demonstrated that intermittent PTH_1-34 treatment enhances and accelerates the skeletal repair process via a number of mechanisms, which include effects on mesenchymal stem cells, angiogenesis, chondrogenesis, bone formation and resorption. Furthermore, PTH_1-34 has been shown to enhance bone repair in challenged animal models of aging, inflammatory arthritis and glucocorticoid-induced bone loss. This pre-clinical success has led to off-label clinical use and a number of case reports documenting PTH_1-34 treatment of delayed-unions and non-unions have been published. Although a recently completed phase 2 clinical trial of PTH_1-34 treatment of patients with radius fracture has failed to achieve its primary outcome, largely because of effective healing in the placebo group, several secondary outcomes are statistically significant, highlighting important issues concerning the appropriate patient population for PTH_1-34 therapy in skeletal repair. Here, we review our current knowledge of the effects of PTH_1-34 therapy for bone healing, enumerate several critical unresolved issues (e.g., appropriate dosing regimen and indications) and discuss the long-term potential of this drug as an adjuvant for endogenous tissue engineering.     

Study of enteric pathogens among children in the tropics and effects of prolonged storage of stool samples

The study was performed to compare real-time PCR after nucleic acid extraction directly from stool samples as well as from samples stored and transported on Whatman papers or flocked swabs at ambient temperature in the tropics. In addition, the possible suitability for a clear determination of likely aetiological relevance of PCR-based pathogen detections based on cycle threshold (Ct) values was assessed. From 632 Tanzanian children <5 years of age with and without gastrointestinal symptoms, 466 samples were subjected to nucleic acid extraction and real-time PCR for gastrointestinal viral, bacterial and protozoan pathogens. Equal or even higher frequencies of pathogen detections from Whatman papers or flocked swabs were achieved compared with nucleic acid extraction directly from stool samples. Comparison of the Ct values showed no significant difference according to the nucleic acid extraction strategy. Also, the Ct values did not allow a decision whether a detected pathogen was associated with gastrointestinal symptoms.