Assessing the heterogeneity of a disease spread through a community

A multivariate non-parametric test and a semi-parametric regression model via counting process are proposed for detecting the heterogeneity of a disease spread through a community. The infection rates are allowed to depend on time in an arbitrary manner. Infectious data usually are not completely observed, nevertheless only partial information of the epidemic is needed for the suggested methods. The testing procedures and the associated methods of analysis are illustrated with reference to epidemics of respiratory disease on the Island of Tristan da Cunha in the South Atlantic     

Stochastic mechano-chemical kinetics of molecular motors: A multidisciplinary enterprise from a physicist’s perspective

A molecular motor is made of either a single macromolecule or a macromolecular complex. Just like their macroscopic counterparts, molecular motors “transduce” input energy into mechanical work. All the nano-motors considered here operate under isothermal conditions far from equilibrium. Moreover, one of the possible mechanisms of energy transduction, called Brownian ratchet, does not even have any macroscopic counterpart. But, molecular motor is not synonymous with Brownian ratchet; a large number of molecular motors execute a noisy power stroke, rather than operating as Brownian ratchet. We review not only the structural design and stochastic kinetics of individual single motors, but also their coordination, cooperation and competition as well as the assembly of multi-module motors in various intracellular kinetic processes. Although all the motors considered here execute mechanical movements, efficiency and power output are not necessarily good measures of performance of some motors. Among the intracellular nano-motors, we consider the porters, sliders and rowers, pistons and hooks, exporters, importers, packers and movers as well as those that also synthesize, manipulate and degrade “macromolecules of life”. We review mostly the quantitative models for the kinetics of these motors. We also describe several of those motor-driven intracellular stochastic processes for which quantitative models are yet to be developed. In part I, we discuss mainly the methodology and the generic models of various important classes of molecular motors. In part II, we review many specific examples emphasizing the unity of the basic mechanisms as well as diversity of operations arising from the differences in their detailed structure and kinetics. Multi-disciplinary research is presented here from the perspective of physicists.     

Dynamical characteristics of bacteria clustering by self-generated attractants

Motivated by the recent work on Escherichia coli bacteria clustering [Park, S., Wolanin, P.M., Yuzbashyan, E.A., Lin, H., Darnton, N.C., Stock, J.B., Silberzan, P., Austin, R., 2003. Proc. Natl. Acad. Sci. U.S.A. 100 (24), 13910], we have conducted a computer simulation of E. coli chemotaxis induced by a self-excreted attractant and investigated how bacteria clusters interact through a self-excreted attractant. By modeling the variation of tumbling frequency in the context of phosphorylation rate change, we have investigated the dependency of clustering behavior on the sensitivity of cells to the attractant. We have found that there exists an optimal sensitivity leading to bigger clusters and that the geometry surrounding the cells also plays an important role in localizing the cluster formation. This result suggests that bacterial cluster formation can be reduced by making bacteria more sensitive to attractants, which is opposite to an instinctive way (making them retarded to attractants). In addition, we have studied the effect of an initial cell distribution on clustering.     

Screening of fluorinated materials degrading microbes

Isolation of bacterial strains capable of degrading fluorinated materials was described. 8 strains of Actinobacteria exhibited degradability of ethyl difluoroacetate (DFAc) was accumulated by bacteria, giving difluoroacetic acid and then fluoride ion. Further, 13 strains of Actinobacteria exhibited degradability of fluorobenzene and/or benzotrifluoride. In batch culture, growth of strains on fluorinated materials led to the release of fluoride ion.     

Surface modification of polyester to produce a bacterial cellulose-based vascular prosthetic device

The surface of medical grade polyesters was modified to impart hydrophilic character for attachment to bacterial synthesized cellulose to produce a vascular prosthetic device. The polyesters were treated with UV/ozone, air plasma, and nitrogen plasma for various lengths of time. The unmodified and modified surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and advancing contact angle measurements. The surfaces were then coated with bacterial produced cellulose to study adhesion properties through tensile testing (peel testing). UV/ozone and plasma treatment XPS results indicated an increase in the oxygen concentration in the form of CO(H) on the treated polyester surfaces. The treatment time to reach steady state in the case of air and nitrogen plasmas took the order of seconds, while 7 min and longer were required for UV/ozone treatment. Peel strength tests to measure adhesion of modified polyester to cellulose reached their maximum values when the CO(H) concentrations were at the highest level. It was also at this level that the contact angle measurements showed no further decrease.     

Bakterieninhaltsstoffe,V: Alkylchinoline und derenN-Oxide ausPseudomonas aeruginosa

Alkyl and alkenyl quinolines (so-called Pyo-substances) and theirN-oxides were isolated fromPseudomonas aeruginosa. Structures proposed earlier could be confirmed; a new representative (Pyo V) is described.

IV. Mitt.:A. Römer, H. Budzikiewicz, H. Korth undG. Pulverer, Tetrahedron Letters1979, 509.     

Magnetic resonance imaging: application in musculoskeletal infection

Forty-two patients with clinically suspected osteomyelitis were examined using magnetic resonance imaging (MRI). Twenty-seven patients (64%) had previous surgery or fracture, and 15 (36%) were referred for differentiation of acute osteomyelitis from bone tumors or other pathologic conditions. MRI was compared with computed tomography in 12 cases and with 111In-labeled leukocytes scans in 22. With MRI, 92% of proved infections were detected, and bone and soft-tissue changes were more evident than with routine radiographs, tomography, or computed tomography. In patients with negative cultures and no previous surgery or fracture, it was difficult for MRI to differentiate operative changes from infection. In these patients, 111In-labeled leukocyte images were more specific than MRI.     

Capillary supercritical fluid chromatography of archaebacterial glycerol tetraether lipids

The analysis of bacterial glycerol tetraethers by capillary supercritical fluid chromatography is described. Complete separation of ethers, differing only by the number of cyclopentane rings present in the isopranyl side chains could be achieved. On a 50% methylphenylpolysiloxane coated capillary, the ethers eluted in the order of increasing cyclopentane content. The analysis revealed the presence of two previously unreported structural isomers of glycerol tetraethers. The method can be used qualitatively and quantitatively as a fast and sensitive screening test for such compounds in living organisms and sedimentary organic matter.     

Fingerprinting bacterial strains using ion mobility spectrometry

Ion mobility spectrometry (IMS) is currently in widespread use for the detection and identification of narcotic and explosive compounds without prior sample clean-up or concentration steps. IMS analysis is rapid, less than a minute, and sensitive, with detection limits in the nanogram to picogram range, depending on the target analyte. Our studies indicate that this technique has potential for detection of specific components of bacterial cells and for identification and differentiation of bacterial strains and species within a minute, and with no specialized test kits or reagents required. When microgram quantities of whole bacterial cells are thermally desorbed, complex positive or negative ion patterns (plasmagrams) are obtained. These plasmagrams differ reproducibly for different strains and species and for different conditions of growth, and can be used for the classification and differentiation of specific strains and species of bacteria, including pathogens. Methods for improved ion peak detection, most notably sequential sample desorption at stepped increases in temperature (programmed temperature ramping), are described.     

Immobilized bacterial luciferase and its applications

This review discusses the properties of the bioluminescent bacterial system as well as the methods for immobilization of bacterial luciferases and for their co-immobilization with other enzymes. The analytical systems using immobilized bacterial luciferases and their applications in analytical biochemistry and biotechnology have been described.