The role of body rotation in bacterial flagellar bundling

In bacterial chemotaxis, E. coli cells drift up chemical gradients by a series of runs and tumbles. Runs are periods of directed swimming, and tumbles are abrupt changes in swimming direction. Near the beginning of each run, the rotating helical flagellar filaments which propel the cell form a bundle. Using resistive-force theory, we show that the counter-rotation of the cell body necessary for torque balance is sufficient to wrap the filaments into a bundle, even in the absence of the swirling flows produced by each individual filament

The prevalence of hepatitis B (Australia) antigen in Southern Africa

The prevalence of hepatitis B (Australia) antigen (HBAg) in 38 941 apparently healthy persons of various ethnic groups living in the Transvaal was determined by countercurrent immuno-electrophoresis or by complement fixation. The prevalence was 0,09 - 0,6% in  healthy Whites, 0,9% in Coloured donors, 2,0% in urban Negroes and 7"10 in rural male Blacks. The positivity rate in 444 healthy Black subjects and in 423 Sana (Bushmen) inhabiting areas in the northern and north-western regions of Southern Africa ranged from 2,7 to 15,8%. An assessment of the frequency of HBAg in various tribal groups of either Sana (Bushmen) or rural Blacks indicated that geographical environment might be one of the factors influencing antigenaemia in healthy persons. The prevalence was highest in persons originating from the west coast regions of Southern Africa, in adjoining territories proceeding from the central plateau, and those countries north of this area (9,1 - 13,6%) An intermediate prevalence of 6 - 7% was noted in some regions abutting on the east coast strip, and a lower prevalence was recorded for inland regions, including Lesotho, the eastern Orange Free State, Natal Midlands and Zululand (4 - 4,7%), while the lowest frequency was found in northern Natal and the central Transvaal areas (2 - 3%). A small group of Sana in the north-eastern corner of South West Africa who had an incidence of 2,7% was the only one which did not fit in with the general geographical distribution of HBAg observed.S. Afr. Med. J., 48, 941 (1974)

Twirling Elastica: Kinks, Viscous Drag, and Torsional Stress

Biological filaments such as DNA or bacterial flagella are typically curved in their natural states. To elucidate the interplay of viscous drag, twisting, and bending in the overdamped dynamics of such filaments, we compute the steady-state torsional stress and shape of a rotating rod with a kink. Drag deforms the rod, ultimately extending or folding it depending on the kink angle. For certain kink angles and kink locations, both states are possible at high rotation rates. The agreement between our macroscopic experiments and the theory is good, with no adjustable parameters.Comment: 4 pages, 4 figure

Film support and the challenge of ‘sustainability’: on wing design, wax and feathers, and bolts from the blue

In recognition of the importance of film in generating both economic and cultural value, the UK Labour government set up a new agency – the United Kingdom Film Council (UKFC) – in 2000 with a remit to build a sustainable film industry. But, reflecting a plethora of differing expectations in relation to the purposes behind public support for film, the UKFC's agenda shifted and broadened over the organisation's lifetime (2000–11). Apparently unconvinced by the UKFC's achievements, the Coalition government which came to power in May 2010 announced the Council's abolition and reassigned its responsibilities as part of a general cost-cutting strategy. Based on original empirical research, this article examines how the UKFC's sense of strategic direction was determined, how and why the balance of objectives it pursued changed over time and what these shifts tell us about the nature of film policy and the challenges facing bodies that are charged with enacting it in the twenty-first century

Infants Born Large for Gestational Age and Developmental Attainment in Early Childhood

Objectives To investigate if an association exists between being born large for gestational age (LGA) and verbal ability or externalizing behaviour problems at ages 4-5 years. Method A secondary analysis was conducted using the National Longitudinal Survey of Children and Youth, including singleton births in 2004-2005 followed till 4-5 years ( Results Infants born LGA were not found to be at increased risk for poor verbal ability (aOR: 1.16 [0.49,2.72] and aOR: 0.83 [0.37,1.87] for girls and boys, resp.) or externalizing behaviour problems (aOR: 1.24 [0.52,2.93] and aOR: 1.24 [0.66,2.36] for girls and boys, resp.). Social factors were found to impact developmental attainment. Maternal smoking led to an increased risk for externalizing behaviour problems (aOR: 3.33 [1.60,6.94] and aOR: 2.12 [1.09,4.13] for girls and boys, resp.). Conclusion There is no evidence to suggest that infants born LGA are at increased risk for poor verbal ability or externalizing behaviour problems

Genome-wide analyses of Liberibacter species provides insights into evolution, phylogenetic relationships, and virulence factors.

'Candidatus Liberibacter' species are insect-transmitted, phloem-limited α-Proteobacteria in the order of Rhizobiales. The citrus industry is facing significant challenges due to huanglongbing, associated with infection from 'Candidatus Liberibacter asiaticus' (Las). In order to gain greater insight into 'Ca. Liberibacter' biology and genetic diversity, we have performed genome sequencing and comparative analyses of diverse 'Ca. Liberibacter' species, including those that can infect citrus. Our phylogenetic analysis differentiates 'Ca. Liberibacter' species and Rhizobiales in separate clades and suggests stepwise evolution from a common ancestor splitting first into nonpathogenic Liberibacter crescens followed by diversification of pathogenic 'Ca. Liberibacter' species. Further analysis of Las genomes from different geographical locations revealed diversity among isolates from the United States. Our phylogenetic study also indicates multiple Las introduction events in California and spread of the pathogen from Florida to Texas. Texan Las isolates were closely related, while Florida and Asian isolates exhibited the most genetic variation. We have identified conserved Sec translocon (SEC)-dependent effectors likely involved in bacterial survival and virulence of Las and analysed their expression in their plant host (citrus) and insect vector (Diaphorina citri). Individual SEC-dependent effectors exhibited differential expression patterns between host and vector, indicating that Las uses its effector repertoire to differentially modulate diverse organisms. Collectively, this work provides insights into the evolution of 'Ca. Liberibacter' species, the introduction of Las in the United States and identifies promising Las targets for disease management

The Certification of a European Reference Plasma for Factor VIII, BCR-629.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel