Spo0J and SMC are required for normal chromosome segregation in Staphylococcus aureus.

Bacterial chromosome segregation is an essential cellular process that is particularly elusive in spherical bacteria such as the opportunistic human pathogen Staphylococcus aureus. In this study, we examined the functional significance of a ParB homologue, Spo0J, in staphylococcal chromosome segregation and investigated the role of the structural maintenance of chromosomes (SMC) bacterial condensin in this process. We show that neither spo0J nor smc is essential in S. aureus; however, their absence causes abnormal chromosome segregation. We demonstrate that formation of complexes containing Spo0J and SMC is required for efficient S. aureus chromosome segregation and that SMC localization is dependent on Spo0J. Furthermore, we found that cell division and cell cycle progression are unaffected by the absence of spo0J or smc. Our results verify the role of Spo0J and SMC in ensuring accurate staphylococcal chromosome segregation and also imply functional redundancy or the involvement of additional mechanisms that might contribute to faithful chromosome inheritance

FtsZ does not initiate membrane constriction at the onset of division.

The source of constriction required for division of a bacterial cell remains enigmatic. FtsZ is widely believed to be a key player, because in vitro experiments indicate that it can deform liposomes when membrane tethered. However in vivo evidence for such a role has remained elusive as it has been challenging to distinguish the contribution of FtsZ from that of peptidoglycan-ingrowth. To differentiate between these two possibilities we studied the early stages of division in Escherichia coli, when FtsZ is present at the division site but peptidoglycan synthesizing enzymes such as FtsI and FtsN are not. Our approach was to use correlative cryo-fluorescence and cryo-electron microscopy (cryo-CLEM) to monitor the localization of fluorescently labeled FtsZ, FtsI or FtsN correlated with the septal ultra-structural geometry in the same cell. We noted that the presence of FtsZ at the division septum is not sufficient to deform membranes. This observation suggests that, although FtsZ can provide a constrictive force, the force is not substantial at the onset of division. Conversely, the presence of FtsN always correlated with membrane invagination, indicating that allosteric activation of peptidoglycan ingrowth is the trigger for constriction of the cell envelope during cell division in E. coli

Cell shape-independent FtsZ dynamics in synthetically remodeled bacterial cells.

FtsZ is the main regulator of bacterial cell division. It has been implicated in acting as a scaffolding protein for other division proteins, a force generator during constriction, and more recently, as an active regulator of septal cell wall production. FtsZ assembles into a heterogeneous structure coined the Z-ring due to its resemblance to a ring confined by the midcell geometry. Here, to establish a framework for examining geometrical influences on proper Z-ring assembly and dynamics, we sculpted Escherichia coli cells into unnatural shapes using division- and cell wall-specific inhibitors in a micro-fabrication scheme. This approach allowed us to examine FtsZ behavior in engineered Z-squares and Z-hearts. We use stimulated emission depletion (STED) nanoscopy to show that FtsZ clusters in sculpted cells maintain the same dimensions as their wild-type counterparts. Based on our results, we propose that the underlying membrane geometry is not a deciding factor for FtsZ cluster maintenance and dynamics in vivo

Detecting Gold Biomineralization by Delftia acidovorans Biofilms on a Quartz Crystal Microbalance

© 2019 American Chemical Society. The extensive use of gold in sensing, diagnostics, and electronics has led to major concerns in solid waste management since gold and other heavy metals are nonbiodegradable and can easily accumulate in the environment. Moreover, gold ions are extremely reactive and potentially harmful for humans. Thus, there is an urgent need to develop reliable methodologies to detect and possibly neutralize ionic gold in aqueous solutions and industrial wastes. In this work, by using complementary measurement techniques such as quartz crystal microbalance (QCM), atomic force microscopy, crystal violet staining, and optical microscopy, we investigate a promising biologically induced gold biomineralization process accomplished by biofilms of bacterium Delftia acidovorans. When stressed by Au3+ ions, D. acidovorans is able to neutralize toxic soluble gold by excreting a nonribosomal peptide, which forms extracellular gold nanonuggets via complexation with metal ions. Specifically, QCM, a surface-sensitive transducer, is employed to quantify the production of these gold complexes directly on the D. acidovorans biofilm in real time. Detailed kinetics obtained by QCM captures the condition for maximized biomineralization yield and offers new insights underlying the biomineralization process. To the best of our knowledge, this is the first study providing an extensive characterization of the gold biomineralization process by a model bacterial biofilm. We also demonstrate QCM as a cheap, user-friendly sensing platform and alternative to standard analytical techniques for studies requiring high-resolution quantitative details, which offers promising opportunities in heavy-metal sensing, gold recovery, and industrial waste treatment

Cell shape independent FtsZ dynamics in synthetically remodeled cells

The FtsZ protein is a key regulator of bacterial cell division. It has been implicated in acting as a scaffolding protein for other division proteins, being a force generator during constriction, and more recently, as an active regulator of septal cell wall production. During an early stage of the division cycle, FtsZ assembles into a heterogeneous structure coined the “Z-ring” due to its resemblance to a ring confined by the midcell geometry. While in vitro experiments on supported lipid bilayers have shown that purified FtsZ can self-organize into a swirling ring roughly the diameter of a bacterial cell, it is not known how, and if, membrane curvature affects FtsZ assembly and dynamics in vivo . To establish a framework for examining geometrical influences on proper Z-ring assembly and dynamics, we sculptured Escherichia coli cells into unnatural shapes, such as squares and hearts, using division- and cell wall-specific inhibitors in a micro fabrication scheme. This approach allowed us to examine FtsZ behavior in engineered “Z-squares” and “Z-hearts”, and in giant cells up to 50 times their normal volume. Quantification of super-resolution STimulated Emission Depletion (STED) nanoscopy data showed that FtsZ densities in sculptured cells maintained the same dimensions as their wild-type counterparts. Additionally, time-resolved fluorescence measurements revealed that FtsZ dynamics were generally conserved in a wide range of cell shapes. Based on our results, we conclude that the underlying membrane environment is not a deciding factor for FtsZ filament maintenance and treadmilling in vivo

Extensive central nervous system involvement in Merkel cell carcinoma: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Merkel cell carcinoma is a rare malignant cutaneous neoplasm that is locally invasive and frequently metastasizes to lymph nodes, liver, lungs, bone and brain. The incidence of Merkel cell carcinoma has increased in the past three decades.</p> <p>Case presentation</p> <p>A 65-year-old Caucasian man presented with a sudden onset of severe headache and a three-month history of balance disturbance. Magnetic resonance imaging revealed a large meningeal metastasis. The radiologic workup showed retroperitoneal and inguinal lymph node metastases. Biopsy of the inguinal lymph nodes showed metastases of Merkel cell carcinoma. Biopsy from three different suspected skin lesions revealed no Merkel cell carcinoma, and the primary site of Merkel cell carcinoma remained unknown. Leptomeningeal metastases, new axillary lymph node metastases, and intraspinal (epidural and intradural) metastases were detected within six, seven and eight months, respectively, from the start of symptoms despite treating the intracranial metastasis with gamma knife and the abdominal metastases with surgical dissection and external radiotherapy. This indicates the aggressive nature of the disease.</p> <p>Conclusion</p> <p>To the best of our knowledge, this is the first report in the literature of an intracranial meningeal metastasis of Merkel cell carcinoma treated with gamma knife and of intraspinal intradural metastases of Merkel cell carcinoma. Despite good initial response to radiotherapy, recurrence and occurrence of new metastases are common in Merkel cell carcinoma.</p

Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb Collisions

The production of neutral pions in 158AGeV Pb+Pb collisions has been studied in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions are compared to various models. The centrality dependence of the neutral pion spectral shape and yield is investigated. An invariance of the spectral shape and a simple scaling of the yield with the number of participating nucleons is observed for centralities with greater than about 30 participating nucleons which is most naturally explained by assuming an equilibrated system.Comment: 5 pages, Latex, including 3 eps figures, submitted to Phys.Rev.Lett; updated pQCD comparison due to new input from the author, updated references, corrected plotting error in figure