Protonation state of F420H2 in the prodrug-activating deazaflavin dependent nitroreductase (Ddn) from Mycobacterium tuberculosis

The protonation state of the deazaflavin dependent nitroreductase (Ddn) enzyme bound cofactor F420 was investigated using UV-visible spectroscopy and computational simulations. The reduced cofactor F420H2 was determined to be present in its deprotonated state in the holoenzyme form. The mechanistic implications of these findings are discussed.MLC and CJJ gratefully acknowledge funding from the Australian Research Council in the form of Discovery Project funding (DP130102144) and ARC Future Fellowships. MLC also acknowledges generous allocations of supercomputing time on the National Facility of the Australian National Computational Infrastructure

fanditha and sihuru: Social and Political Import of Muslim-dhivehi Knowledge Forms

Muslim-dhivehi inhabitants of the Maldives bold indigenous knowledge forms called fanditha and sihuru. These practices may loosely be categorized in English as “sorcery.” As a “native” anthropologist, I contend that both fanditha and sihuru practices function as sociopolitical critique. For individuals who believe in the causality of these practices, fanditha and sihuru have, respectively, productive and destructive potentialities in regards to the human body and psyche. Using an analytical framework that interprets these practices processually, I maintain that fanditha and sihuru have the potential to heal fractured social relationships. These practices attempt to fix the perceived material inequalities that may suddenly arise between kin members. Inflicting sihuru onto one’s kin makes them accountable for the changing sociality that one attributes to changing material conditions. Through an examination of the constructions of Muslim-dhivehi personhood and community, I discuss how violence in the form of sihuru engenders closer social relationships rather than animosity. I also argue that these indigenous knowledge forms, when they are disregarded in favor of western knowledge forms by state organizations and development agencies, have the potential to fracture sociopolitical relationships. This is a form of injustice by the state. This argument adds to the existing body of anthropological work on the implications of using emic and etic perspectives when two cultural streams converge. This thesis is an ethnography about Muslim-dhivehi fanditha and sihuru beliefs amongst some dhivehin to illustrate a fragment of the diversities and complexities that comprise the Maldives

An evaluation of the surveillance system for dengue virus infections in Maldives

AbstrAct background: Dengue is endemic in Maldives. The largest epidemic to date was in 2011. This study evaluates the surveillance system for dengue during 2011, identifies gaps and suggests ways to improve

Economic analysis of dengue prevention and case management in the Maldives.

As tourism is the mainstay of the Maldives' economy, this country recognizes the importance of controlling mosquito-borne diseases in an environmentally responsible manner. This study sought to estimate the economic costs of dengue in this Small Island Developing State of 417,492 residents. The authors reviewed relevant available documents on dengue epidemiology and conducted site visits and interviews with public health offices, health centers, referral hospitals, health insurers, and drug distribution organizations. An average of 1,543 symptomatic dengue cases was reported annually from 2011 through 2016. Intensive waste and water management on a resort island cost $1.60 per occupied room night. Local vector control programs on inhabited islands cost$35.93 for waste collection and $7.89 for household visits by community health workers per person per year. Ambulatory care for a dengue episode cost$49.87 at a health center, while inpatient episodes averaged $127.74 at a health center,$1,164.78 at a regional hospital, and $1,655.50 at a tertiary referral hospital. Overall, the cost of dengue illness in the Maldives in 2015 was$2,495,747 (0.06% of gross national income, GNI, or $6.10 per resident) plus$1,338,141 (0.03% of GNI or $3.27 per resident) for dengue surveillance. With tourism generating annual income of$898 and tax revenues of $119 per resident, results of an international analysis suggest that the risk of dengue lowers the country's gross annual income by$110 per resident (95% confidence interval $50 to$160) and its annual tax receipts by $14 per resident (95$7 to $22). Many innovative vector control efforts are affordable and could decrease future costs of dengue illness in the Maldives

Lactase can target cellular differentiation of Acanthamoeba castellanii belonging to the T4 genotype

The free living Acanthamoeba spp. are ubiquitous amoebae associated with potentially blinding disease known as Acanthamoeba keratitis (AK) and a fatal central nervous system infection granulomatous amoebic encephalitis (GAE). With the inherent ability of cellular differentiation, it can phenotypically transform to a dormant cyst form from an active trophozoite form. Acanthamoeba cysts are highly resistant to therapeutic agents as well as contact lens cleaning solutions. One way to tackle drug resistance against Acanthamoeba is by inhibiting the formation of cysts from trophozoites. The biochemical analysis showed that the major component of Acanthamoeba cyst wall is composed of carbohydrate moieties such as galactose and glucose. The disaccharide of galactose and glucose is lactose. In this study, we analyzed the potential of lactase enzyme to target carbohydrate moieties of cyst walls. Amoebicidal assessment showed that lactase was ineffective against trophozoite of A. castellanii but enhanced amoebicidal effects of chlorhexidine. The lactase enzyme did not show any toxicity against normal human keratinocyte cells (HaCaT) at the tested range. Hence, lactase can be used for further assessment for development of potential therapeutic agents in the management of Acanthamoeba infection as well as formulation of effective contact lens disinfectants.</p

FAD-sequestering proteins protect mycobacteria against hypoxic and oxidative stress

The ability to persist in the absence of growth triggered by low oxygen levels is a critical process for the survival of mycobacterial species in many environmental niches. MSMEG_5243 (fsq), a gene of unknown function in Mycobacterium smegmatis, is up-regulated in response to hypoxia and regulated by DosRDosS/DosT, an oxygen- and redox-sensing two-component system that is highly conserved in mycobacteria. In this communication, we demonstrate that MSMEG_5243 is a flavin-sequestering protein and henceforth refer to it as Fsq. Using an array of biochemical and structural analyses, we show that Fsq is a member of the diverse superfamily of flavin- and deazaflavin-dependent oxidoreductases (FDORs) and is widely distributed in mycobacterial species. We created a markerless deletion mutant of fsq and demonstrate that fsq is required for cell survival during hypoxia. Using fsq deletion and overexpression, we found that fsq enhances cellular resistance to hydrogen peroxide treatment. The X-ray crystal structure of Fsq, solved to 2.7 Å, revealed a homodimeric organization with FAD bound noncovalently. The Fsq structure also uncovered no potential substrate-binding cavities, as the FAD is fully enclosed, and electrochemical studies indicated that the Fsq:FAD complex is relatively inert and does not share common properties with electron-transfer proteins. Taken together, our results suggest that Fsq reduces the formation of reactive oxygen species (ROS) by sequestering free FAD during recovery from hypoxia, thereby protecting the cofactor from undergoing autoxidation to produce ROS. This finding represents a new paradigm in mycobacterial adaptation to hypoxia.This work was supported by the Maurice Wilkins Centre for Molecular Biodiscovery and the Marsden Fund, Royal Society, New Zealand. This work was also supported by a University of Otago Doctoral Scholarship and a Sandy Smith Scholarship (to L. K. H.) and by a CSIRO OCE Postdoctoral Fellowship, ARC DECRA Fellowship DE170100310, and NHMRC New Investigator Grant APP1139832 (to C. G.). In addition, this work was supported by NHMRC Project Grant APP1128929 (to C. J. J., C. G., and G. M. C.)

The methanogenic redox cofactor F420 is widely synthesized by aerobic soil bacteria

F420 is a low-potential redox cofactor that mediates the transformations of a wide range of complex organic compounds. Considered one of the rarest cofactors in biology, F420 is best known for its role in methanogenesis and has only been chemically identified in two phyla to date, the Euryarchaeota and Actinobacteria. In this work, we show that this cofactor is more widely distributed than previously reported. We detected the genes encoding all five known F420 biosynthesis enzymes (cofC, cofD, cofE, cofG and cofH) in at least 653 bacterial and 173 archaeal species, including members of the dominant soil phyla Proteobacteria, Chloroflexi and Firmicutes. Metagenome datamining validated that these genes were disproportionately abundant in aerated soils compared with other ecosystems. We confirmed through high-performance liquid chromatography analysis that aerobically grown stationary-phase cultures of three bacterial species, Paracoccus denitrificans, Oligotropha carboxidovorans and Thermomicrobium roseum, synthesized F420, with oligoglutamate sidechains of different lengths. To understand the evolution of F420 biosynthesis, we also analyzed the distribution, phylogeny and genetic organization of the cof genes. Our data suggest that although the Fo precursor to F420 originated in methanogens, F420 itself was first synthesized in an ancestral actinobacterium. F420 biosynthesis genes were then disseminated horizontally to archaea and other bacteria. Together, our findings suggest that the cofactor is more significant in aerobic bacterial metabolism and soil ecosystem composition than previously thought. The cofactor may confer several competitive advantages for aerobic soil bacteria by mediating their central metabolic processes and broadening the range of organic compounds they can synthesize, detoxify and mineralize.This work was supported by Australian Research Council research Grants (DE120102673, DP130102144) awarded to CJJ; Australian National University Summer and PhD scholarships awarded respectively to BN and FHA; and a CSIRO Office of the Chief Executive Postdoctoral Fellowship awarded to C