The flaAlI.2, flaQ, and flaN genes of Salmonella typhimurium are important for assembly, rotation, and counterclockwise-clockwise switching of the flagellar motor. Paralyzed and nonchemotactic mutants were subjected to selection pressure for partial acquisition of motility and chemotaxis, and the suppressor mutations of the resulting pseudorevertants were mapped and isolated. Many of the intergenic suppressor mutations were in one of the other two genes. Others were in genes for cytoplasmic components of the chemotaxis system, notably cheY and cheZ; one of the mutations was found in the cheA gene and one in a motility gene, motB. (14), i.e., it contains a binary switch. The switch operates even in unstimulated cells; stimijli bias the switching events in a way that results in migration toward more favorable environments (3, 17).The motors are located at the cell surface. After digestion of the peptidoglycan layer and dissolution of the outer and cytoplasmic membranes, a structure can be isolated which is termed the flagellar basal body and consists of four rings and a rod (7,8). A variety of evidence, including a recent study of Salmonella typhimurium (1), indicates that the basal body is not the entire motor. It does not contain any of the proteins known to be involved in the two central functions of the motor, conversion of proton motive force into rotational work and switching between the two rotational senses.Five proteins are known to play important roles in rotation and switching. They are MotA and MotB (6,9,25,28,29,33) and FlaAII.2, FlaQ, and FlaN (4,5,9,11,12,19,22,23,26,[31][32][33]

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A Salmonella typhimurium strain possessing a mutation in thefliF gene (coding for the component protein of the M ring of the flageilar basal body) swarmed poorly on a semisolid plate. However, cells grown in liquid medium swam normally and did not show any differences from wild-type cells in terms of swimming speed or tumbling frequency. When mutant cells were grown in a viscous medium, detached bundles of flagellar ifiaments as long as 100 ,um were formed and the cells had impaired motility. Electron microscopy and immunoelectron microscopy revealed that the filaments released from the cells had the hook and a part of the rod of the flagellar basal body still attached. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis showed that the rod portion of the released structures consisted of the 30-kilodalton FlgG protein. Double mutants containing this fliF mutation and various che mutations were constructed, and their behavior in viscous media was analyzed. When the flagellar rotation of the mutants was strongly biased to either a counterclockwise or a clockwise direction, detached bundles were not formed. The formation of large bundles was most extreme in mutants weakly biased to clockwise rotation.

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Although hepatitis B (HBV) and C (HCV) virus infections are still global health issues, measuring sero-markers by standard venipuncture is challenging in areas limited with the adequate human resources and basic infrastructure. This study aimed to inform the usefulness of dried blood spot (DBS) sampling technique for epidemiological study of HBV and HCV in the resources limited areas. We compared specimen recovery rate expressed as analytical sensitivity ratio of HBsAg, HBcAb and anti-HCV between serum specimens and DBS samples (HemaSpot vs Whatman903). Sensitivity ratio was calculated as the ratio of the measured value from DBS to the measured value from serum. Then both the qualitative and quantitative comparisons of HBsAg detection by DBS were done using Cambodian samples. HBsAg, HBcAb and anti-HCV sensitivity ratios for the highest sample dilution (8fold) were 31.2:1, 38.9:1 and 32.0:1 for Whatman903 card and 17.6:1, 23.5:1 and 26.3:1 for HemaSpot respectively. Detection efficacy of HemaSpot (80%) was not inferior to Whatman903 (60%) after 1 month storage, and no significant difference in any hepatitis virus sero-markers was observed in HemaSpot-spotted patient samples stored for 2 weeks at −25 °C and 29 °C. All reference HemaSpot-spotted 400 HBsAg sero-negative samples showed negative. Sensitivity and specificity of HBsAg in HemaSpot were 92.3% and 100%. The recovery expressed as analytical sensitivity ratio of HBsAg, HBcAb and anti-HCV of HemaSpot specimen were not inferior to Whatman903. Therefore, DBS with its usefulness proved as an acceptable tool for large epidemiological study of HBV and HCV in resources limited remote area. Hepatitis B virus (HBV) and hepatitis C virus (HCV) constitute a global health issue. Although there are the effective hepatitis B vaccine since 1982 1 and anti-viral drugs such as interferon alpha, lamivudine and others (tenofovir, adefovir, etc) 2,3 , WHO reported that approximately 257 million people have been infected with HBV and only 16.7% of the people diagnosed with hepatitis B were on anti-viral treatment as of 2016 4. Similarly, even there is no vaccine for HCV till now, the direct-acting antiviral drugs (DAAs) for the treatment of HCV were initially developed in 2011 5 and have since yielded high sustained virologic responses (SVRs) 6. But, WHO reported that 71 million people have been chronically infected with HCV and approximately 19% of global population (13.1 millions) knew their diagnosis and around 5 million only had treated with DAA at the end of 2017 7. Therefore, the World Health Organization (WHO) announced in 2016 a target to eliminate HBV as public health threats by 2030 by reducing the hepatitis B surface antigen (HBsAg) prevalence among children to ≤0.1% 8 and to eliminate HCV by 90% reduction in new diagnosis and 65% reduction in HCV related mortality by 2030 9. However, both