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Dissecting regulatory mechanisms of quorum sensing pathways in Bacillus subtilis
Living organisms generally share a small number of characteristics, among which include maintaining homeostasis, growth, and responding to changing environments. Wherever we find life, we typically observe this life performing these tasks. Likely no environment is truly barren, so organisms must be able to continue living in crowded conditions. Humans use their senses to determine the quality of their local environment. Individuals use languages, written, spoken and digital to communicate these findings to their neighbors. Bacteria have evolved complex systems to sense these conditions, and to trigger appropriate developmental programs to help them survive, grow, and respond in changing environments. Bacteria both produce and sense signals about these density-dependent conditions in a process called quorum sensing.
Chapter 1 provides an introduction to the mechanisms utilized by bacteria referred to as quorum sensing. An overview is given of the history of the study of these mechanisms, as well as a review of molecules and strategies from both Gram-negative and Gram-positive organisms. Also discussed here are mechanisms of quorum quenching used by organisms in quorum sensing pathways. Next, we discuss in some detail the molecular mechanisms used by Bacillus subtilis to regulate pathways under control of the quorum response.
Chapter 2 describes work looking to further explain the mechanism of ComA activation. In this chapter, we use a genetic screen to identify constitutive mutants of ComA. We then characterize these mutants for their regulation by ComP and RapC and for their ability to bind DNA. These results were used in an attempt to generate a computational model of ComA activation. We take preliminary steps in validating this model by logically creating and testing combination mutants of ComA. The role of acetyl-phosphate in ComA activation is also briefly explored.
Chapter 3 explores the role of Rap proteins in regulating the biological processes of genetic competence, sporulation, motility and biofilm formation. We were able to characterize several Rap proteins as novel regulators of these pathways. We also were able to show that Rap60 uses a separate surface for interaction with ComA as compared to canonical Rap protein anti-activators of genetic competence
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Associations between physical activity and BMI, body fatness, and visceral adiposity in overweight or obese Latino and non-Latino adults.
Background/objectivesAlthough several studies have reported associations between moderate to vigorous physical activity (MVPA), body fatness and visceral adipose tissue (VAT), the extent to which associations differ among Latinos and non-Latinos remains unclear. This study evaluated the associations between body composition and MVPA in Latino and non-Latino adults.Subjects/methodsAn exploratory, cross-sectional analysis was conducted using baseline data collected from 298 overweight adults enrolled in a 12-month randomized controlled trial that tested the efficacy of text messaging to improve weight loss. MVPA, body fatness and VAT were assessed by waist-worn accelerometry, dual-energy x-ray absorptiometry (DXA), and DXA-derived software (GE CoreScan GE, Madison, WI, USA), respectively. Participants with <5 days of accelerometry data or missing DXA data were excluded; 236 participants had complete data. Multivariable linear regression assessed associations between body composition and MVPA per day, defined as time in MVPA, bouts of MVPA (time per bout ⩾10 min), non-bouts of MVPA (time per bout <10 min) and meeting the 150-min MVPA guideline. The modifying influence of ethnicity was modeled with a multiplicative interaction term.ResultsThe interaction between ethnicity and MVPA in predicting percent body fat was significant (P=0.01, 95% confidence interval (CI) (0.58, 4.43)) such that a given increase in MVPA was associated with a greater decline in total body fat in non-Latinos compared with Latinos (adjusted for age, sex and accelerometer wear time). There was no interaction between ethnicity and MVPA in predicting VAT (g) (P=0.78, 95% CI (-205.74, 273.17)) and body mass index (BMI) (P=0.18, 95% CI (-0.49, 2.26)).ConclusionsAn increase in MVPA was associated with a larger decrease in body fat, but neither BMI nor VAT, in non-Latinos compared with Latinos. This suggests that changes in VAT and BMI in response to MVPA may be less influenced by ethnicity than is total body fatness
34 Emergency language documentation teams: the Cape York Peninsula experience
Language revitalisation and endangered language documentation are complementary endeavours – they feed into each other and both benefit from the support of the other. This idea is at the heart of a community teams approach called Emergency Language Documentation Teams (McConvell et al. 2005). This paper will review the underpinnings of this idea and discuss the successes and difficulties encountered while applying it in the Cape York Peninsula region. The findings of the Cape York Peninsula Language Documentation project pilot discussed in this paper include that informal approaches to both language worker training and language learning were, across the board, far more successful than more formal approaches (including one-on-one versions of master-apprentice schemes). We also found that the project approach was more difficult in situations where there were more social and linguistic divisions and heterogeneity. There is some irony in this given that often in the Australian context linguistic homogeneity within a speech community can itself be a result of language shift and language loss
Junior Recital: Patrick J. Hill, Horn
Kemp Recital Hall Saturday Afternoon March 23, 1996 2:00p.m
Zeeman Slowers for Strontium based on Permanent Magnets
We present the design, construction, and characterisation of longitudinal-
and transverse-field Zeeman slowers, based on arrays of permanent magnets, for
slowing thermal beams of atomic Sr. The slowers are optimised for operation
with deceleration related to the local laser intensity (by the parameter
), which uses more effectively the available laser power, in contrast
to the usual constant deceleration mode. Slowing efficiencies of up to
are realised and compared to those predicted by modelling.
We highlight the transverse-field slower, which is compact, highly tunable,
light-weight, and requires no electrical power, as a simple solution to slowing
Sr, well-suited to spaceborne application. For Sr we achieve a slow-atom
flux of around atomss at ms, loading
approximately atoms in to a magneto-optical-trap (MOT), and
capture all isotopes in approximate relative natural abundances
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