An Essential Staphylococcus Aureus Cell Division Protein Directly Regulates FtsZ Dynamics

Binary fission has been well studied in rod-shaped bacteria, but the mechanisms underlying cell division in spherical bacteria are poorly understood. Rod-shaped bacteria harbor regulatory proteins that place and remodel the division machinery during cytokinesis. In the spherical human pathogen Staphylococcus aureus, we found that the essential protein GpsB localizes to mid-cell during cell division and co-constricts with the division machinery. Depletion of GpsB arrested cell division and led to cell lysis, whereas overproduction of GpsB inhibited cell division and led to the formation of enlarged cells. We report that S. aureus GpsB, unlike other Firmicutes GpsB orthologs, directly interacts with the core divisome component FtsZ. GpsB bundles and organizes FtsZ filaments and also stimulates the GTPase activity of FtsZ. We propose that GpsB orchestrates the initial stabilization of the Z-ring at the onset of cell division and participates in the subsequent remodeling of the divisome during cytokinesis

Deciphering the Role of a SLOG Superfamily Protein YpsA in Gram-Positive Bacteria

Bacteria adapt to different environments by regulating cell division and several conditions that modulate cell division have been documented. Understanding how bacteria transduce environmental signals to control cell division is critical in understanding the global network of cell division regulation. In this article we describe a role for Bacillus subtilis YpsA, an uncharacterized protein of the SLOG superfamily of nucleotide and ligand-binding proteins, in cell division. We observed that YpsA provides protection against oxidative stress as cells lacking ypsA show increased susceptibility to hydrogen peroxide treatment. We found that the increased expression of ypsA leads to filamentation and disruption of the assembly of FtsZ, the tubulin-like essential protein that marks the sites of cell division in B. subtilis. We also showed that YpsA-mediated filamentation is linked to the growth rate. Using site-directed mutagenesis, we targeted several conserved residues and generated YpsA variants that are no longer able to inhibit cell division. Finally, we show that the role of YpsA is possibly conserved in Firmicutes, as overproduction of YpsA in Staphylococcus aureus also impairs cell division

Genetic Dissection of Strain Dependent Paraquat-induced Neurodegeneration in the Substantia Nigra Pars Compacta

The etiology of the vast majority of Parkinson's disease (PD) cases is unknown. It is generally accepted that there is an interaction between exposures to environmental agents with underlying genetic sensitivity. Recent epidemiological studies have shown that people living in agricultural communities have an increased risk of PD. Within these communities, paraquat (PQ) is one of the most utilized herbicides. PQ acts as a direct redox cycling agent to induce formation of free radicals and when administered to mice induces the cardinal symptoms of parkinsonism, including loss of TH+-positive dopaminergic (DA) neurons in the ventral midbrain's substantia nigra pars compacta (SNpc). Here we show that PQ-induced SNpc neuron loss is highly dependent on genetic background: C57BL/6J mice rapidly lose ∼50% of their SNpc DA neurons, whereas inbred Swiss-Webster (SWR/J) mice do not show any significant loss. We intercrossed these two strains to map quantitative trait loci (QTLs) that underlie PQ-induced SNpc neuron loss. Using genome-wide linkage analysis we detected two significant QTLs. The first is located on chromosome 5 (Chr 5) centered near D5Mit338, whereas the second is on Chr 14 centered near D14Mit206. These two QTLs map to different loci than a previously identified QTL (Mptp1) that controls a significant portion of strain sensitivity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), suggesting that the mechanism of action of these two parkinsonian neurotoxins are different

To Mid-cell and Beyond: Characterizing the Roles of GpsB and YpsA in Cell Division Regulation in Gram-positive Bacteria

The bacterial cell division protein FtsZ is a tubulin homolog that forms a ring-like structure at the site of cell division in most bacterial species. There it acts as a scaffold, aiding in the recruitment of other divisome proteins to the site of cell division. Furthermore, studies focusing on the role of FtsZ treadmilling and septal peptidoglycan synthesis implicates that FtsZ plays a direct role in the ultimate closure of the division septum. Thus, many studies in the field of bacterial cell division have focused on FtsZ in terms of its spatial and temporal regulation as well as its ability to interact with other division proteins. The finding that cells lacking well- studied regulators of FtsZ activity still divide at wild type like capacities suggests the existence of other yet to be discovered factors involved in the cell division process. Work in our lab has focused on the identification and characterization of novel regulators of cell division in the rod- shaped model organism, Bacillus subtilis, and in the spherical bacterium, Staphylococcus aureus. Here, we describe the function of YpsA, previously annotated as a protein of unknown function, and GpsB in B. subtilis and S. aureus respectively. Our results indicate that YpsA provides oxidative stress protection in B. subtilis cells. Furthermore, YpsA appears to be functioning as a growth rate-dependent cell division inhibitor, though the mechanism by which YpsA elicits this function has not yet been identified. It is interesting to note that this proposed function of YpsA, as well as the growth rate dependency, is also conserved in S. aureus. Sequence and structural analysis of YpsA allowed for the identification of several amino acid residues critical for the ability of YpsA to elicit filamentation. We have also found that disruption of a conserved substrate binding groove, through site directed mutagenesis, resulted in an impairment of YpsA-GFP foci formation in addition to cell division inhibition. That had indicated a link between foci formation and the ability of YpsA to inhibit cell division. A follow up study utilizing a screen to identify intragenic and extragenic suppressors of YpsA-mediated filamentation allowed for the identification of additional amino acid residues important for the function of YpsA, many of which also lined the predicted DNA binding groove. Using this screen, we were also able to isolate an extragenic suppressor mutation in yfhS, which was annotated as a sporulation gene based on transcriptomics data. Our results indicate that YfhS may also play a role in cell size regulation during vegetative growth, as cells harboring yfhS null mutations appeared smaller in both length and width when compared to a wild type control. Collectively, these results constituted the first reports on the role of YpsA in cell division in B. subtilis. Our study focusing on GpsB in S. aureus indicated a role for GpsB in regulating the dynamics of FtsZ during the cell cycle. Our results indicate that production of S. aureus GpsB in B. subtilis is lethal and results in severe filamentation indicative of cell division inhibition. Furthermore, overexpression of gpsB in S. aureus also resulted in cell division inhibition, and depletion of intracellular GpsB levels resulted in a lethal phenotype thereby confirming its essentiality in S. aureus. Fluorescence microscopy revealed that GpsB localization was dynamic during the cell cycle as GpsB-GFP was observed at the leading edge of the invaginating membrane. In combination with in vitro analysis of GpsB suggesting a direct interaction with FtsZ, we propose a model where GpsB in S. aureus forms lateral interactions between FtsZ protofilaments. This increases the local concentrations of FtsZ at the division site and subsequently triggers FtsZ protofilament disassembly via GpsB activity, and ultimately contributes to FtsZ treadmilling facilitating septum closure

Positive and Negative Themes Depicted in Combat-Related Sports Films

Participation in boxing, mixed martial arts, and wrestling is extremely popular among children and adolescents. The objective of this study was to determine themes depicted in a select number of combat-related films. Twenty films were independently viewed and analyzed by 4 reviewers. The average number of positive and negative themes was 34.4 and 18.1 mean events/hour for all included films, respectively. The most common positive themes were “positive interactions with family/friends/fans,” “importance of mentorship,” and “positive interactions with a coach/trainer” (4.23, 3.63, and 3.06 mean events/hour, respectively). The most common negative themes were “choosing to do the wrong thing,” “negative interactions with family/friends/fans,” and “poor sportsmanship” (2.70, 2.00, and 1.58 mean events/hour, respectively). In conclusion, the co-viewing of combat-related films among pediatric athletes and their coaches/trainers and/or parents in order to focus on “teachable moments” may encourage the acquisition and development of positive themes and the avoidance and de-emphasis of negative themes

Historical impact to drive research in peptic ulcer disease

The story of gastric acid secretion began with early ideas on gastric secretion (Spallanzani and de Réaumur, 17th century) and with first descriptions of food digestion (Dupuytren and Bichat, Beaumont, early 18th century), followed by proof that gastric juice contained acid (Prout, early 18th century). The research continued with first descriptions of gastric glands as the source of gastric acid and its changes upon digestive stimulus (Purkinje and Golgi, mid and late 19th century). The theory of 'nervism' - the neuro-reflex stimulation of gastric secretion by vagal nerve (Pavlov, early 20th century) was contrasted by a histamine-mediated concept of gastric secretion (Popielski and Code, mid 20th century). Thus, gastric acid and pepsin (Schwann, early 19th century) were found to be essential for food digestion and studies also pointed to histamine, being the most potent final common chemostimulator of oxyntic cells. The discoveries in etiopathogenesis of mucosal injury were marked by the famous dictum: 'No acid, no ulcer' ('Ohne saueren Magensaft kein peptisches Geschwür', Schwarz, 1910) that later induced the term of 'mucosal defense' and the notion that the breaking of 'gastric mucosal barrier' represents the initial step in the process of mucosal injury (Davenport, Code and Scholer, mid 20th century). The prostaglandins were shown to influence all major components of gastric mucosal barrier, described with the term 'cytoprotection' (Vane, Robert and Jacobson, 1970s). Beginning in the latter half of 19th century, the studies on gastric bacteriology that followed enabled the discovery of association between Campylobacter (Helicobacter) pylori and peptic ulcers (Warren and Marshall, 1980s) that led to worldwide major interventions in treating peptic ulcer disease. The surgical approach to peptic ulcer had been outlined by resection procedures (Billroth, Pean, Moynihan, late 19 century) and vagotomy, with or without drainage procedures (Jaboulay, Latarjet, Dragstedt, mid 20th century). Antacids, protective agents, anticholinergics, and later gastrin antagonists and prostaglandins were used for decades in the treatment of peptic ulcer, with differing effects. The advent of the concept of H(2)-receptor antagonists (Black, 1970s) and the discovery of acid (proton) pumps in parietal cells (Ganser, Forte and Sachs, late 1970s) paved the way for potent (H(2) antagonists) and profound acid inhibition (proton pump inhibitors) that revolutionized the treatment of acid-related disorders, including peptic ulcer disease. Worldwide, peptic ulcer and its complications remain the cause of significant morbidity, especially in older age groups, representing a major burden for ambulatory and hospital healthcare resources

Supramolecular Kandinsky Circles with High Antibacterial Activity

Nested concentric structures widely exist in nature and designed systems with circles, polygons, polyhedra, and spheres sharing the same center or axis. It still remains challenging to construct discrete nested architecture at (supra)molecular level. Herein, three generations (G2−G4) of giant nested supramolecules, or Kandinsky circles, have been designed and assembled with molecular weight 17,964, 27,713 and 38,352 Da, respectively. In the ligand preparation, consecutive condensation between precursors with primary amines and pyrylium salts is applied to modularize the synthesis. These discrete nested supramolecules are prone to assemble into tubular nanostructures through hierarchical self-assembly. Furthermore, nested supramolecules display high antimicrobial activity against Gram-positive pathogen methicillin-resistant Staphylococcus aureus (MRSA), and negligible toxicity to eukaryotic cells, while the corresponding ligands do not show potent antimicrobial activity