Mycobacterium tuberculosis, the causative agent of tuberculosis, is one of the most important bacterial pathogens. Recent work has revealed that the natural bactericidal properties of copper are ...utilized by the host immune system to combat infections with bacteria, including M. tuberculosis. However, M. tuberculosis employs multiple mechanisms to reduce the internal copper amount by efflux and sequestration, which are required for virulence of M. tuberculosis. Here, we describe an alternative mechanism of copper resistance by M. tuberculosis. Deletion of the rv0846c gene increased the susceptibility of M. tuberculosis to copper at least 10-fold, establishing Rv0846c as a major component of copper resistance in M. tuberculosis. In vitro assays showed that Rv0846c oxidized organic substrates and Fe(II). Importantly, mutation of the predicted copper-coordinating cysteine 486 resulted in inactive Rv0846c protein which did not protect M. tuberculosis against copper stress. Hence, Rv0846c is a multicopper oxidase of M. tuberculosis and was renamed mycobacterial multicopper oxidase (MmcO). MmcO is membrane associated, probably by lipidation after export across the inner membrane by the twin-arginine translocation system. However, mutation of the lipidation site did not affect the oxidase activity or the copper protective function of MmcO. Our study revealed MmcO as an important copper resistance mechanism of M. tuberculosis, which possibly acts by oxidation of toxic Cu(I) in the periplasm.
Electronic activity monitors (such as those manufactured by Fitbit, Jawbone, and Nike) improve on standard pedometers by providing automated feedback and interactive behavior change tools via mobile ...device or personal computer. These monitors are commercially popular and show promise for use in public health interventions. However, little is known about the content of their feedback applications and how individual monitors may differ from one another.
The purpose of this study was to describe the behavior change techniques implemented in commercially available electronic activity monitors.
Electronic activity monitors (N=13) were systematically identified and tested by 3 trained coders for at least 1 week each. All monitors measured lifestyle physical activity and provided feedback via an app (computer or mobile). Coding was based on a hierarchical list of 93 behavior change techniques. Further coding of potentially effective techniques and adherence to theory-based recommendations were based on findings from meta-analyses and meta-regressions in the research literature.
All monitors provided tools for self-monitoring, feedback, and environmental change by definition. The next most prevalent techniques (13 out of 13 monitors) were goal-setting and emphasizing discrepancy between current and goal behavior. Review of behavioral goals, social support, social comparison, prompts/cues, rewards, and a focus on past success were found in more than half of the systems. The monitors included a range of 5-10 of 14 total techniques identified from the research literature as potentially effective. Most of the monitors included goal-setting, self-monitoring, and feedback content that closely matched recommendations from social cognitive theory.
Electronic activity monitors contain a wide range of behavior change techniques typically used in clinical behavioral interventions. Thus, the monitors may represent a medium by which these interventions could be translated for widespread use. This technology has broad applications for use in clinical, public health, and rehabilitation settings.
Type III secretion systems (T3SSs) are protein transport nanomachines that are found in Gram-negative bacterial pathogens and symbionts. Resembling molecular syringes, T3SSs form channels that cross ...the bacterial envelope and the host cell membrane, which enable bacteria to inject numerous effector proteins into the host cell cytoplasm and establish trans-kingdom interactions with diverse hosts. Recent advances in cryo-electron microscopy and integrative imaging have provided unprecedented views of the architecture and structure of T3SSs. Furthermore, genetic and molecular analyses have elucidated the functions of many effectors and key regulators of T3SS assembly and secretion hierarchy, which is the sequential order by which the protein substrates are secreted. As essential virulence factors, T3SSs are attractive targets for vaccines and therapeutics. This Review summarizes our current knowledge of the structure and function of this important protein secretion machinery. A greater understanding of T3SSs should aid mechanism-based drug design and facilitate their manipulation for biotechnological applications.
The pathogenesis of Salmonella Typhimurium depends on the bacterium's ability to survive and replicate within host cells. The formation and maintenance of a unique membrane-bound compartment, termed ...the Salmonella-containing vacuole (SCV), is essential for S. Typhimurium pathogenesis. SCV-bound S. Typhimurium induces formation of filamentous tubules that radiate outwards from the SCV, termed Salmonella-induced filaments (SIFs). SIF formation is concomitant with the onset of replication within host epithelial cells. SIF biogenesis, formation and maintenance of the SCV, and the intracellular positioning of the SCV within the host cell requires translocation of bacterial proteins (effectors) into the host cell. Effectors secreted by the type III secretion system encoded on Salmonella pathogenicity island 2 (T3SS2) function to interfere with host cellular processes and promote both intracellular survival and replication of S. Typhimurium. Seven T3SS2-secreted effectors, SifA, SopD2, PipB2, SteA, SseJ, SseF, and SseG have previously been implicated to play complementary, redundant, and/or antagonistic roles with respect to SIF biogenesis, intracellular positioning of the SCV, and SCV membrane dynamics modulation during infection. We undertook a systematic study to delineate the contribution of each effector to these processes by (i) deleting all seven of these effectors in a single S. Typhimurium strain; and (ii) deleting combinations of multiple effectors based on putative effector function. Using this deletion mutant library, we show that each of SIF biogenesis, intracellular SCV localization, intramacrophage replication, colonization, and virulence depends on the activities of multiple effectors. Together, our data demonstrates the complex interplay between these seven effectors and highlights the necessity to study T3SS2-secreted effectors as groups, rather than studies of individual effectors.
Summary Mycobacterium tuberculosis is an important bacterial pathogen with an extremely slow growth rate, an unusual outer membrane of very low permeability and a cunning ability to survive inside ...the human host despite a potent immune response. A key trait of M. tuberculosis is to acquire essential nutrients while still preserving its natural resistance to toxic compounds. In this regard, copper homeostasis mechanisms are particularly interesting, because copper is an important element for bacterial growth, but copper overload is toxic. In M. tuberculosis at least two enzymes require copper as a cofactor: the Cu/Zn-superoxide dismutase SodC and the cytochrome c oxidase which is essential for growth in vitro . Mutants of M. tuberculosis lacking the copper metallothionein MymT, the efflux pump CtpV and the membrane protein MctB are more susceptible to copper indicating that these proteins are part of a multipronged system to balance intracellular copper levels. Recent evidence showed that part of copper toxicity is a reversible damage of Fe–S clusters of dehydratases and the displacement of other divalent cations such as zinc and manganese as cofactors in proteins. There is accumulating evidence that macrophages use copper to poison bacteria trapped inside phagosomes. Here, we review the rapidly increasing knowledge about copper homeostasis in M. tuberculosis and contrast those with similar mechanisms in Escherichia coli . These findings reveal an intricate interplay between the host which aims to overload the phagosome with copper and M. tuberculosis which utilizes several mechanisms to reduce the toxic effects of excess copper.
The appeal of using microbial inoculants to mediate plant traits and productivity in managed ecosystems has increased over the past decade, because microbes represent an alternative to fertilizers, ...pesticides, and direct genetic modification of plants. Using microbes bypasses many societal and environmental concerns because microbial products are considered a more sustainable and benign technology. In our desire to harness the power of plant–microbial symbioses, are we ignoring the possibility of precipitating microbial invasions, potentially setting ourselves up for a microbial Jurassic Park? Here, we outline potential negative consequences of microbial invasions and describe a set of practices (Testing, Regulation, Engineering, and Eradication, TREE) based on the four stages of invasion to prevent microbial inoculants from becoming invasive. We aim to stimulate discussion about best practices to proactively prevent microbial invasions.
Positive results from using microbes in restoration and agricultural research coupled with changing technology have led to increased interest in scaling up and commercializing microbial inoculants as biostimulants and bioprotectants.Ecological research has not kept pace with agricultural and microbiome research with regards to the effect that these introduced microbes have on resident plant and soil communities, and the resulting ecosystem services. Are we unleashing, or have we already unleashed, a tool meant for the betterment of society that we cannot control and may wreak havoc ecologically?Here, we discuss potential consequences of human-assisted microbial invasions. We review current regulatory structures in the USA and provide a general set of practices to decrease the probability of microbial inoculants escaping their intended use and becoming invasive
Polyethylene is a widely used plastic exhibiting a large range of properties that depend on molecular weight, crystallinity, chain branching, and cross-linking. In this study, the sound speeds and ...elastic properties of a variety of commercially available polyethylene materials were experimentally determined using the pulse-echo ultrasound technique. In situ pressure dependent measurements, including ultrasound time of flight, x-ray diffraction, and x-ray radiography, were performed using a Paris-Edinburgh large volume press at the High Pressure Collaborative Access Team (HPCAT), beamline 16-BM-B at the Advanced Photon Source. Polyethylene sound speed and elastic moduli were found to increase with increasing pressure. The zero pressure orthorhombic phase was found to transform to monoclinic at low pressures of ~0.1 GPa.
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•Sound speed and elastic constants in polyethylene increase with increasing density.•Sound speed sharply increases at low pressure due to compression of free volume.•Stress-induced martensitic phase transformation observed at very low pressure.
Abstract Children and adolescents with physical and cognitive disabilities have a higher prevalence of overweight compared to their non-disabled peers. This health risk can lead to a greater number ...of obesity-related secondary conditions (e.g., fatigue, pain, deconditioning, social isolation, difficulty performing activities of daily living) and can impose significant personal and economic hardship on the child and family. Effective strategies for reducing the risk of overweight/obesity in adolescents with disabilities must begin with greater awareness of the behavioral and environmental antecedents that lead to higher rates of obesity in this underserved segment of the youth population. Research on interventions to reduce obesity among adolescents with disabilities is an important area of future research for public health scientists. A range of interventions will be necessary to overcome the many barriers that youth with disabilities experience in achieving and maintaining a healthy weight.
Summary
Sphingomyelinases secreted by pathogenic bacteria play important roles in host–pathogen interactions ranging from interfering with phagocytosis and oxidative burst to iron acquisition. This ...study shows that the Mtb protein Rv0888 possesses potent sphingomyelinase activity cleaving sphingomyelin, a major lipid in eukaryotic cells, into ceramide and phosphocholine, which are then utilized by Mtb as carbon, nitrogen and phosphorus sources, respectively. An Mtb rv0888 deletion mutant did not grow on sphingomyelin as a sole carbon source anymore and replicated poorly in macrophages indicating that Mtb utilizes sphingomyelin during infection. Rv0888 is an unusual membrane protein with a surface‐exposed C‐terminal sphingomyelinase domain and a putative N‐terminal channel domain that mediated glucose and phosphocholine uptake across the outer membrane in an M. smegmatis porin mutant. Hence, we propose to name Rv0888 as SpmT (sphingomyelinase of Mycobacterium tuberculosis). Erythrocyte membranes contain up to 27% sphingomyelin. The finding that Rv0888 accounts for half of Mtb's hemolytic activity is consistent with its sphingomyelinase activity and the observation that Rv0888 levels are increased in the presence of erythrocytes and sphingomyelin by 5‐ and 100‐fold, respectively. Thus, Rv0888 is a novel outer membrane protein that enables Mtb to utilize sphingomyelin as a source of several essential nutrients during intracellular growth.
Many pathogenic bacteria secrete sphingomyelinases that hydrolyze sphingomyelin, a major lipid in eukaryotic cells. We identified Rv0888 of Mycobacterium tuberculosis as the first protein with coupled surface sphingomyelinase and channel domains. The enzymatic activity of Rv0888 enhances intracellular replication of Mtb in human macrophages, lyses cells and enables nutrient uptake. These functions also explain the stimulating activity of sphingomyelin on growth of Mtb which was first described in 1948 and contact hemolysis by Mtb.
The trafficking patterns of the bacterial regulators of transcript elongation σ
70, ρ, NusA, and NusG on genes in vivo and the explanation for promoter-proximal peaks of RNA polymerase (RNAP) are ...unknown. Genome-wide,
E. coli ChIP-chip revealed distinct association patterns of regulators as RNAP transcribes away from promoters (ρ first, then NusA, then NusG). However, the interactions of elongating complexes with these regulators did not differ significantly among most transcription units. A modest variation of NusG signal among genes reflected increased NusG interaction as transcription progresses, rather than functional specialization of elongating complexes. Promoter-proximal RNAP peaks were offset from σ
70 peaks in the direction of transcription and co-occurred with NusA and ρ peaks, suggesting that the RNAP peaks reflected elongating, rather than initiating, complexes. However, inhibition of ρ did not increase RNAP levels within genes downstream from the RNAP peaks, suggesting the peaks are caused by a mechanism other than ρ-dependent attenuation.
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