Tree of motility – A proposed history of motility systems in the tree of life

Motility often plays a decisive role in the survival of species. Five systems of motility have been studied in depth: those propelled by bacterial flagella, eukaryotic actin polymerization and the eukaryotic motor proteins myosin, kinesin and dynein. However, many organisms exhibit surprisingly diverse motilities, and advances in genomics, molecular biology and imaging have showed that those motilities have inherently independent mechanisms. This makes defining the breadth of motility nontrivial, because novel motilities may be driven by unknown mechanisms. Here, we classify the known motilities based on the unique classes of movement-producing protein architectures. Based on this criterion, the current total of independent motility systems stands at 18 types. In this perspective, we discuss these modes of motility relative to the latest phylogenetic Tree of Life and propose a history of motility. During the ~4 billion years since the emergence of life, motility arose in Bacteria with flagella and pili, and in Archaea with archaella. Newer modes of motility became possible in Eukarya with changes to the cell envelope. Presence or absence of a peptidoglycan layer, the acquisition of robust membrane dynamics, the enlargement of cells and environmental opportunities likely provided the context for the (co)evolution of novel types of motility

A child with anorexia nervosa presenting with severe infection with cytopenia and hemophagocytosis: a case report

Abstract Background Patients with anorexia nervosa in the acute phase have physical complications, such as infectious disease. Although hemophagocytic syndrome due to infection is a rare complication in anorexia nervosa, early identification for hemophagocytosis is important for avoiding a life-threatening condition. Case presentation We report a case of a 12-year-old girl with anorexia nervosa presenting with infection with cytopenia and hemophagocytosis during initial nutritional therapy. She developed pyrexia, abdominal pain, and diarrhea during inpatient treatment. Although intravenous antibiotics were administered, the symptoms persisted. Acinetobacter baumannii was detected in blood culture. Hemophagocytosis was present in the bone marrow. Gamma globulin therapy was effective, with improvement in symptoms and cytopenia. Conclusions Although our case did not fulfill the criteria of hemophagocytic syndrome, clinicians should consider severe infection in anorexia nervosa with cytopenia and hemophagocytosis

Stochastic Signal Processing and Transduction in Chemotactic Response of Eukaryotic Cells

Single-molecule imaging analysis of chemotactic response in eukaryotic cells has revealed a stochastic nature in the input signals and the signal transduction processes. This leads to a fundamental question about the signaling processes: how does the signaling system operate under stochastic fluctuations or noise? Here, we report a stochastic model of chemotactic signaling in which noise and signal propagation along the transmembrane signaling pathway by chemoattractant receptors can be analyzed quantitatively. The results obtained from this analysis reveal that the second-messenger-production reactions by the receptors generate noisy signals that contain intrinsic noise inherently generated at this reaction and extrinsic noise propagated from the ligand-receptor binding. Such intrinsic and extrinsic noise limits the directional sensing ability of chemotactic cells, which may explain the dependence of chemotactic accuracy on chemical gradients that has been observed experimentally. Our analysis also reveals regulatory mechanisms for signal improvement in the stochastically operating signaling system by analyzing how the SNR of chemotactic signals can be improved on or deteriorated by the stochastic properties of receptors and second-messenger molecules. Theoretical consideration of noisy signal transduction by chemotactic signaling systems can further be applied to signaling systems in general