Attachment and Biofilm Forming Capabilities of Staphylococcus epidermidis Strains Isolated from Preterm Infants

Staphylococcus epidermidis, a human commensal, is an important opportunistic, biofilm-forming pathogen and the main cause of late onset sepsis in preterm infants, worldwide. In this study we describe the characteristics of S. epidermidis strains causing late onset (>72 h) bloodstream infection in preterm infants and skin isolates from healthy newborns. Attachment and biofilm formation capability were analyzed in microtiter plates and with transmission electron microscopy (TEM). Clonal relationship among strains was studied with pulsed-field gel electrophoresis. Antimicrobial susceptibility testing was performed, as well as the detection of biofilm-associated genes and of the invasiveness marker IS256 with polymerase chain reaction. Blood and skin isolates had similar attachment and biofilm-forming capabilities and biofilm formation was not related to the presence of specific genes. Filament-like membrane structures were seen by TEM early in the attachment close to the device surface, both in blood and skin strains. Nine of the ten blood isolates contained the IS256 and were also resistant to methicillin and gentamicin in contrast to skin strains. S. epidermidis strains causing bloodstream infection in preterm infants exhibit higher antibiotic resistance and are provided with an invasive genetic equipment compared to skin commensal strains. Adhesion capability to a device surface seems to involve bacterial membrane filaments.     

Survival of thermophilic and hyperthermophilic microorganisms after exposure to UV-C,ionizing radiation and desiccation

In this study, we investigated the ability of several (hyper-) thermophilic Archaea and phylogenetically deep-branching thermophilic Bacteria to survive high fluences of monochromatic UV-C (254 nm) and high doses of ionizing radiation, respectively. Nine out of fourteen tested microorganisms showed a surprisingly high tolerance against ionizing radiation, and two species (Aquifex pyrophilus and Ignicoccus hospitalis) were even able to survive 20 kGy. Therefore, these species had a comparable survivability after exposure to ionizing radiation such as Deinococcus radiodurans. In contrast, there was nearly no difference in survival of the tested strains after exposure to UV-C under anoxic conditions. If the cells had been dried in advance of UV-C irradiation, they were more sensitive to UV-C radiation compared with cells irradiated in liquid suspension; this effect could be reversed by the addition of protective material like sulfidic ores before irradiation. By exposure to UV-C, photoproducts were formed in the DNA of irradiated Archaea and Bacteria. The distribution of the main photoproducts was species specific, but the amount of the photoproducts was only partly dependent on the applied fluence. Overall, our results show that tolerance to radiation seems to be a common phenomenon among thermophilic and hyperthermophilic microorganisms.     

A period of transient viremia and occult infection precedes persistent viremia and antiviral immune responses during multiple low-dose intravaginal simian immunodeficiency virus inoculations

In rhesus macaques, classic systemic infection, characterized by persistent viremia and seroconversion, occurred after multiple low-dose (10(3) 50% tissue culture infective doses) intravaginal (IVAG) inoculations with simian immunodeficiency virus (SIV) strain SIVmac251. Monkeys developed classic SIV infections after a variable number of low-dose IVAG exposures to SIVmac251. Once established, the systemic infection was identical to SIV infection following high-dose IVAG SIV inoculation. However, occult systemic infection characterized by transient cell-associated or cell-free viremia consistently occurred early in the series of multiple vaginal SIV exposures. Further, antiviral cellular immune responses were present prior to the establishment of a classic systemic infection in the low-dose vaginal SIV transmission model.     

Up-regulation of vimentin expression in low-density malignant glioma cells as immediate and late effects under irradiation and temozolomide treatment

Nervous system tumors are one of the leading causes of cancer related death. Specific mechanisms facilitating the invasive behavior of gliomas remain obscure. Advanced simulation models of the in vivo response to therapy conditions should potentially improve malignant glioma treatment. Expressional profiling of vimentin––one of reliable pro-invasive tumor makers––in those simulation models was the goal of this study, in order to estimate a pro-invasive response of surviving malignant glioma cells under clinically relevant therapeutic conditions. Human U87-MG malignant glioma cells were used. These cells are characterized by the wild p53-phenotype, which is relevant for the majority of primary malignant glioblastomas. Experimental design foresaw the cells to undergo either irradiation or chemo-treatment with temozolomide alone, or combined treatment. Expression profiling of vimentin was performed by quantitative “Real-Time”-PCR under all treatment conditions simulating diverse tumor regions. Here we demonstrated that vimentin expression patterns in human malignant glioma cells strongly depend on cellular density, algorithms of drug delivery and chemo/radio treatment. Substantial differences were recognized between immediate and late therapy effects. Significant increase in vimentin expression levels was detected particularly in low-density cell cultures under durable treatment with constant concentration levels of temezolomide. Simulation of variable intratumoral regional conditions (central intratumoral regions vs. disseminated malignant cells in peripheral regions) demonstrated differential response of vimentin expression in malignant glioma cell cultures treated under clinically relevant conditions. Slight ebbing of expression levels as late effects of the treatment in confluent cultures may correspond to necrotic processes clinically observed in central intratumoral regions. Contrary, in disseminated malignant cells of peripheral regions therapy resulted in vimentin-inducing effects. This is in agreement with the clinical observations of an increased aggressiveness and malignancy grade of post-operatively chemo/radio-treated malignant gliomas.     

Intravascular plug formation induced by poly-APS is the principal mechanism of the toxin's lethality in rats/rat tissues

Toxic water soluble polymeric 3-alkylpyridinium salts isolated from the sponge Raniera sarai strongly inhibited AChE in vitro. In vivo, experimental animals died due to plugs formed in microcirculation. The mechanism of this plug formation is unknown. In vitro, the toxin did not affect the coagulation rate, but the rate of platelet aggregation was accelerated in a dose-dependent manner. The hemolytic activity of poly-APS was diminished by the addition of serum proteins in a dose-dependent manner. These results support the conclusion that non-specific binding to proteins is the underlying mechanism of the lethality of poly APS.     

Structural Basis for Auto-Inhibition of the NDR1 Kinase Domain by an Atypically Long Activation Segment

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Adaptive laboratory evolution of microbial co‐cultures for improved metabolite secretion

Adaptive laboratory evolution has proven highly effective for obtaining microorganisms with enhanced capabilities. Yet, this method is inherently restricted to the traits that are positively linked to cell fitness, such as nutrient utilization. Here, we introduce coevolution of obligatory mutualistic communities for improving secretion of fitness‐costly metabolites through natural selection. In this strategy, metabolic cross‐feeding connects secretion of the target metabolite, despite its cost to the secretor, to the survival and proliferation of the entire community. We thus co‐evolved wild‐type lactic acid bacteria and engineered auxotrophic Saccharomyces cerevisiae in a synthetic growth medium leading to bacterial isolates with enhanced secretion of two B‐group vitamins, viz., riboflavin and folate. The increased production was specific to the targeted vitamin, and evident also in milk, a more complex nutrient environment that naturally contains vitamins. Genomic, proteomic and metabolomic analyses of the evolved lactic acid bacteria, in combination with flux balance analysis, showed altered metabolic regulation towards increased supply of the vitamin precursors. Together, our findings demonstrate how microbial metabolism adapts to mutualistic lifestyle through enhanced metabolite exchange.