What's new and notable in bacterial spore killing!

Spores of many species of the orders Bacillales and Clostridiales can be vectors for food spoilage, human diseases and intoxications, and biological warfare. Many agents are used for spore killing, including moist heat in an autoclave, dry heat at elevated temperatures, UV radiation at 254 and more recently 222 and 400 nm, ionizing radiation of various types, high hydrostatic pressures and a host of chemical decontaminants. An alternative strategy is to trigger spore germination, as germinated spores are much easier to kill than the highly resistant dormant spores-the so called "germinate to eradicate" strategy. Factors important to consider in choosing methods for spore killing include the: (1) cost; (2) killing efficacy and kinetics; (3) ability to decontaminate large areas in buildings or outside; and (4) compatibility of killing regimens with the: (i) presence of people; (ii) food quality; (iii) presence of significant amounts of organic matter; and (iv) minimal damage to equipment in the decontamination zone. This review will summarize research on spore killing and point out some common flaws which can make results from spore killing research questionable

REPRESENTING THE DISPERSION OF EMISSIONS FROM AIRCRAFT ON RUNWAYS

Aircraft in their takeoff ground run constitute an unavoidable strong source of emissions subject to a highly variable motion. The intermittent nature of release makes it difficult to measure the emissions and establish their impact on mean concentrations in the vicinity of airports. Practically, it is also difficult to perform experimental studies near taxiways and runways. Remote observations have nevertheless recently been obtained by a rapidly-swept UV Lidar, and analysis of these has necessitated and informed a parallel modelling effort. Aircraft exhausts disperse in a complex manner, as they are subject not only to transport processes of the ambient atmosphere, but also to those associated with the aircraft itself (with diffusion in ambient turbulence to be expected once turbulence resulting from the aircraft falls to ambient levels). They have a downstream Lagrangian momentum associated with the engine thrust, and steadily acquire a vertical momentum as a result of their buoyancy. Exhaust streams merge and interact strongly with the ground to form a common emission plume within about a wingspan downstream of engines’ exits. Before the aircraft reaches a threshold speed, is rotated upward and lifts off, the downstream (thrust) forcing and upstream source acceleration are approximately constant, and a first-order nonlinear partial differential equation may be expressed capturing the turbulent diffusion of the plume in the reference frame of the source. The downstream forcing exceeds the buoyant forcing, so the plume remains in contact with the ground, but is heightened and narrowed by buoyant rise. During rotation and liftoff, the net downstream forcing declines as a significant airframe drag arises, and the source acceleration plummets. More importantly, lift on the airframe and the associated shed circulation cause exhausts to move downward and, in proximity to ground, outward, so their dynamics decouple from those of exhausts released earlier, with re-coupling unlikely before the aircraft has turned in its flight path. Once rotation is initiated, this argues for a simplifying (and partly analytic) treatment of the exhaust plume generated earlier, such that the turbulent diffusion of a given elemental plume segment is taken to match that of an infinitely long flow tube (with the latter ascribed the same buoyancy density and downstream Lagrangian momentum density – or mass flux – throughout)

Recombinant expression of insoluble enzymes in Escherichia coli: a systematic review of experimental design and its manufacturing implications.

Recombinant enzyme expression in Escherichia coli is one of the most popular methods to produce bulk concentrations of protein product. However, this method is often limited by the inadvertent formation of inclusion bodies. Our analysis systematically reviews literature from 2010 to 2021 and details the methods and strategies researchers have utilized for expression of difficult to express (DtE), industrially relevant recombinant enzymes in E. coli expression strains. Our review identifies an absence of a coherent strategy with disparate practices being used to promote solubility. We discuss the potential to approach recombinant expression systematically, with the aid of modern bioinformatics, modelling, and 'omics' based systems-level analysis techniques to provide a structured, holistic approach. Our analysis also identifies potential gaps in the methods used to report metadata in publications and the impact on the reproducibility and growth of the research in this field.Non

Plasmid-encoded genes influence exosporium assembly and morphology in Bacillus megaterium QM B1551 spores.

Spores of Bacillus megaterium QM B1551 are encased in a morphologically distinctive exosporium. We demonstrate here that genes encoded on the indigenous pBM500 and pBM600 plasmids are required for exosporium assembly and or stability in spores of this strain. Bioinformatic analyses identified genes encoding orthologues of the B. cereus-family exosporium nap and basal layer proteins within the B. megaterium genome. Transcriptional analyses, supported by electron and fluorescent microscopy, indicate that the pole-localized nap, identified here for the first time in B. megaterium QM B1551 spores, is comprised of the BclA1 protein. The role of the BxpB protein, which forms the basal layer of the exosporium in B. cereus spores, is less clear since spores of a null mutant strain display an apparently normal morphology. Retention of the localized nap in bxpB null spores suggests that B. megaterium employs an alternative mechanism to that used by B. cereus spores in anchoring the nap to the spore surface.Julia Manetsberger was the recipient of an EPSRC Doctoral Training grant. The assistance of Dr. Jeremy Skepper (University of Cambridge), Caitlin Brumby and Professor Per Bullough (both University of Sheffield) with electron microscopy work is gratefully acknowledged. The authors have no conflicts of interest to declare.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/femsle/fnv14

Structural and functional analysis of SleL, a peptidoglycan lysin involved in germination of Bacillus spores.

A major event in the germination of Bacillus spores concerns hydrolysis of the cortical peptidoglycan that surrounds the spore protoplast, the integrity of which is essential for maintenance of dormancy. Cortex degradation is initiated in all species of Bacillus spores by the combined activity of two semi-redundant cortex-lytic enzymes, SleB and CwlJ. A third enzyme, SleL, which has N-acetylglucosaminidase activity, cleaves peptidoglycan fragments generated by SleB and CwlJ. Here we present crystal structures of B. cereus and B. megaterium SleL at 1.6 angstroms and 1.7 angstroms, respectively. The structures were determined with a view to identifying the structural basis of differences in catalytic efficiency between the respective enzymes. The catalytic (α/β)8 -barrel cores of both enzymes are highly conserved from a structural perspective, including the spatial distribution of the catalytic residues. Both enzymes are equipped with two N-terminal peptidoglycan-binding LysM domains, which are also structurally highly conserved. However, the topological arrangement of the respective enzymes second LysM domain is markedly different, and this may account for differences in catalytic rates by impacting upon the position of the active sites with respect to their substrates. A chimeric enzyme comprising the B. megaterium SleL catalytic domain plus B. cereus SleL LysM domains displayed enzymatic activity comparable to the native B. cereus protein, exemplifying the importance of the LysM domains to SleL function. Similarly, the reciprocal construct, comprising the B. cereus SleL catalytic domain with B. megaterium SleL LysM domains, showed reduced activity compared with native B. cereus SleL.The crystallographic experiments were performed in the Crystallographic X7ray Facility (CXF) at the Department of Biochemistry, University of Cambridge. DYC was supported by CXF.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/prot.2486

Crystal structure of the PepSY-containing domain of the YpeB protein involved in germination of bacillus spores.

The crystal structure of the C-terminal domain of the Bacillus megaterium YpeB protein has been solved by X-ray crystallography to 1.80-Å resolution. The full-length protein is essential in stabilising the SleB cortex lytic enzyme in Bacillus spores, and may have a role in regulating SleB activity during spore germination. The YpeB-C crystal structure comprises three tandemly repeated PepSY domains, which are aligned to form an extended laterally compressed molecule. A predominantly positively charged region located in the second PepSY domain may provide a site for protein interactions that are important in stabilising SleB and YpeB within the spore.The author acknowledges support from various sources including the new lecturers' start up funding from Cambridge University and a donation from the Government Decontamination Service.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/prot.2486

A Model for the Impact of Task Complexity on Deception in a Group Decision Making Task

This paper reports the results of a pilot study of a group decision making task. A research model and hypotheses are presented related to the larger main study which has yet to be conducted. The purpose of this series of studies is to investigate the impact of task complexity on truthful and deceptive participants in a group computer mediated communication (CMC) scenario. The pilot study tests perceived task difficulty when task complexity is manipulated. The results show the desired difference in task complexity is perceived by the participants. These results set the stage for the next phase of this study in which a deception manipulation will be introduced

Orthologues of Bacillus subtilis Spore Crust Proteins Have a Structural Role in the Bacillus megaterium QM B1551 Spore Exosporium.

The exosporium of Bacillus megaterium QM B1551 spores is morphologically distinct from exosporia observed for the spores of many other species. Previous work has demonstrated that unidentified genes carried on one of the large indigenous plasmids are required for the assembly of the Bacillus megaterium exosporium. Here, we provide evidence that pBM600-encoded orthologues of the Bacillus subtilis CotW and CotX proteins, which form the crust layer in spores of that species, are structural components of the Bacillus megaterium QM B1551 spore exosporium. The introduction of plasmid-borne cotW and orthologous cotX genes to the PV361 strain, which lacks all indigenous plasmids and produces spores that are devoid of an exosporium, results in the development of spores with a rudimentary exosporium-type structure. Additionally, purified recombinant CotW protein is shown to assemble at the air-water interface to form thin sheets of material, which is consistent with the idea that this protein may form a basal layer in the Bacillus megaterium QM B1551 exosporium.IMPORTANCE When starved of nutrients, some bacterial species develop metabolically dormant spores that can persist in a viable state in the environment for several years. The outermost layers of spores are of particular interest since (i) these represent the primary site for interaction with the environment and (ii) the protein constituents may have biotechnological applications. The outermost layer, or exosporium, in Bacillus megaterium QM B1551 spores is of interest, as it is morphologically distinct from the exosporia of spores of the pathogenic Bacillus cereus family. In this work, we provide evidence that structurally important protein constituents of the Bacillus megaterium exosporium are different from those in the Bacillus cereus family. We also show that one of these proteins, when purified, can assemble to form sheets of exosporium-like material. This is significant, as it indicates that spore-forming bacteria employ different proteins and mechanisms of assembly to construct their external layers.Julia Manetsberger was the recipient of an EPSRC studentship, awarded from the departmental block DTG

Patterns and determinants of acute psychiatric readmissions

Objectives. Deinstitutionalisation and shortage of psychiatric beds worldwide has led to extensive research into the risk factors and interventions associated with rapid and recurrent admission to hospital. Little research of this nature has taken place in South Africa, particularly with regard to acute hospital admissions. This study attempted primarily to assess the effect of length of stay and administration of depot antipsychotics in hospital on time to readmission.Design. A retrospective cohort of 180 admissions was followed up for 12 months, after an index discharge, by means of multiple hospital and community-based record reviews. Each readmission was analysed as an event using a survival analysis model.Setting. Chris Hani Baragwanath Hospital, Gauteng.Subjects. A random sample of patients admitted during a 6- month period in 1996.Outcome measures. Time to readmission.Results. Two hundred and eighty-four admissions were analysed. The only factor that provided a significant protective effect was being married or cohabiting (P = 0.015). Clinic attendance showed a slight protective effect early on but conferred a significantly higher risk of readmission on those who had been out of hospital for a long period (P = 0.001). Only 21 % of discharged patients ever attended a clinic. The overall risk of readmission was significantly higher in the first 90 days post discharge.Conclusions. The lack of impact of length of hospital stay and use of depot neuroleptics on time to readmission may indicate that patients are being kept for appropriate duration and that the most ill patients are receiving depot medication.Several sampling and statistical artefacts may explain some of our findings. These results confirm the worldwide difficulty in finding consistent and accurate predictors of readmission. Low rates of successful referral to community aftercare need to be addressed before their effectiveness can be reasonably assessed. The inherent instability of the post-discharge period is a potential area for further investigation and intensive management

Structure-function analysis of the Bacillus megaterium GerUD spore germinant receptor protein.

Germination of Bacillus spores is triggered by the interaction of germinant molecules with specialized receptor proteins localized to the spore inner membrane. Germinant receptors (GRs) are comprised typically of three interacting protein subunits, each of which is essential for receptor function. At least some GRs appear to have a fourth component, referred to as a D-subunit protein. A number of D-subunit proteins were shown previously to be capable of modulating the activity of associated GRs. Here, we investigate the topology and structure-function relationships of the Bacillus megaterium QM B1551 GerUD protein, which is associated with the GerU GR. The presented data demonstrate that GerUD can be subjected to relatively extensive structural modifications while retaining function. Indeed, the presence of either of the two transmembrane spanning domains is sufficient to modulate an efficient GerU-mediated germinative response. The precise function of D-subunit proteins has yet to be established, although they may act as molecular chaperones within the spore inner-membrane environment.S.G was the recipient of a RA Fisher bursary award from Gonville and Caius College, University of Cambridge. X.Z is the recipient of an EPSRC Doctoral Training Grant.This is the final version of the article. It was first available from OUP via http://dx.doi.org/10.1093/femsle/fnv21