The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are studying how samples might be brought back to Earth from Mars safely. Backward planetary protection is key in this complex endeavour, as it is required to prevent potential adverse effects from returning materials to Earth's biosphere. As the question of whether or not life exists on Mars today or whether it ever did in the past is still unanswered, the effort to return samples from Mars is expected to be categorized as a ‘Restricted Earth Return’ mission, for which NASA policy requires the containment of any unsterilized material returned to Earth. NASA is investigating several solutions to contain Mars samples and sterilize any uncontained Martian particles. This effort has significant implications for both NASA's scientific mission, and the Earth's environment; and so special care and vigilance are needed in planning and execution in order to assure acceptance of safety to Earth's biosphere. To generate a technically acceptable sterilization process across a wide array of scientific and other stakeholders, on 30–31 January 2019, 10–11 June 2019 and 19–20 February 2020, NASA informally convened a Sterilization Working Group (SWG) composed of experts from industry, academia and government to assess methods for sterilization and inactivation, to identify future work needed to verify these methods against biological challenges, and to determine their feasibility for implementation on robotic spacecraft in deep space. The goals of the SWG were:

1. (1) Understand what it means to sterilize and/or inactivate Martian materials and how that understanding can be applied to the Mars Sample Return (MSR) mission.

2. (2) Assess methods for sterilization and inactivation, and identify future work needed to verify these methods.

3. (3) Provide an effective plan for communicating with other agencies and the public.

This paper provides a summary of the discussions and conclusions of the SWG over these three workshops. It reflects a consensus position based on qualitative discussion of how agencies might approach the problem of sterilization of Mars material. The SWG reached a consensus that sterilization options can be considered on the basis of biology as we know it, and that sterilization modalities that are effective on terrestrial materials and organisms should be part of the MSR planetary protection strategy. Conclusions pointed to several industry standards for sterilization to include heat, chemical, UV radiation and low-heat plasma. Technical trade-offs for each sterilization modality were discussed while simultaneously considering the engineering challenges and limitations for spaceflight. Future work includes more in-depth discussions on technical trade-offs of sterilization modalities, identifying and testing Earth analogue challenge organisms and proteinaceous molecules against chosen modalities, and executing collaborative agreements between NASA and external working group partners to help close data gaps, and to establish strong, scientifically grounded sterilization and inactivation standards for MSR.

The X chromosome is known to play an important role in many sex-specific diseases. However, only a few single-nucleotide polymorphisms on the X chromosome have been found to be associated with diseases. Compared to the autosomes, conducting association tests on the X chromosome is more intractable due to the difference in the number of X chromosomes between females and males. On the other hand, X-chromosome inactivation takes place in female mammals, which is a phenomenon in which the expression of one copy of two X chromosomes in females is silenced in order to achieve the same gene expression level as that in males. In addition, imprinting effects may be related to certain diseases. Currently, there are some existing approaches taking X-chromosome inactivation into account when testing for associations on the X chromosome. However, none of them allows for imprinting effects. Therefore, in this paper, we propose a robust test, ZXCII, which accounts for both X-chromosome inactivation and imprinting effects without requiring specifying the genetic models in advance. Simulation studies are conducted in order to investigate the validity and performance of ZXCII under various scenarios of different parameter values. The simulation results show that ZXCII controls the type I error rate well when there is no association. Furthermore, with regards to power, ZXCII is robust in all of the situations considered and generally outperforms most of the existing methods in the presence of imprinting effects, especially under complete imprinting effects.

The objective of the studies reported in this research communication was to investigate the use of whey contaminated with antibiotics such as cephalosporins, quinolones and tetracyclines as a nutrient medium for the growth of Kluyveromyces marxianus with particular attention to the effect of thermal treatment used to overcome the inhibitory effects of antibiotic concentrations close to the Maximum Residue Limits. The heat treatments at 120 °C for 40 min, 120 °C for 83 min, and 120 °C for 91 min caused total inactivation of cephalosporins, tetracyclines and quinolone residues in whey respectively.

New Zealand has a much higher rate of reported campylobacteriosis cases than the rest of the developed world. It has been assumed that New Zealand C. jejuni strains have greater heat tolerance and thus are better able to survive cooking. Therefore there is a need to fully determine the temperature dependence of Campylobacter spp. and to update the current knowledge of kinetic parameters such as D and z values of Campylobacter spp. The significantly higher reported D- values for Campylobacter spp. already seen in the Netherlands requires a practical stance in ensuring appropriate evaluation of thermal process lethality of Campylobacter spp. An extensive search of data bases for publications on Campylobacter heat resistance was conducted. The kinetic parameters obtained in New Zealand under isothermal and dynamic conditions in broths or in food matrix are broadly in agreement with previously published international data and do not indicate that New Zealand strains are more heat resistant than other strains. This finding has a significant impact to regulators, consumers, food industry and researchers as it has revealed the scientific evidence to maintain the standards for the heat treatment practices. Any change of heat treatment practice can cause unpredicted loss to the poultry industry and challenges the regulatory bodies to convey the message of altering the consumers cooking temperature to all consumers with a short time given the reluctance of consumers in using thermometers to verify the cooking temperature at home. Consumers play an important role in making certain the food they prepare is safe by preventing cross-contamination in order to avoid the risk of food borne diseases.

Bacterial endospores are resistant to many environmental factors from temperature extremes to ultraviolet irradiation and are generally more difficult to inactivate or kill than vegetative bacterial cells. It is often considered necessary to treat spores or samples containing spores with chemical fixative solutions for prolonged periods of time (e.g., 1–21 days) to achieve fixation/inactivation to enable electron microscopy (EM) examination outside of containment laboratories. Prolonged exposure to chemical fixatives, however, can alter the ultrastructure of spores for EM analyses. This study was undertaken to determine the minimum amount of time required to inactivate/sterilize and fix spore preparations from several bacterial species using a universal fixative solution for EM that maintains the ultrastructural integrity of the spores. We show that a solution of 4% paraformaldehyde with 1% glutaraldehyde inactivated spore preparations of Bacillus anthracis, Bacillus cereus, Bacillus megaterium, Bacillus thuringiensis, and Clostridium perfringens in 30 min, and Bacillus subtilis in 240 min. These results suggest that this fixative solution can be used to inactivate and fix spores from several major groups of bacterial spore formers after 240 min, enabling the fixed preparations to be removed from biocontainment and safely analyzed by EM outside of biocontainment.

We review the principles of ultraviolet (UV) irradiation, the inactivation of infectious agents by UV, and current applications for the control of microorganisms. In particular, wavelengths between 200 and 280 nm (germicidal UV) affect the double-bond stability of adjacent carbon atoms in molecules including pyrimidines, purines and flavin. Thus, UV inactivation of microorganisms results from the formation of dimers in RNA (uracil and cytosine) and DNA (thymine and cytosine). The classic application of UV irradiation is the inactivation of microorganisms in biological safety cabinets. In the food-processing industry, germicidal UV irradiation has shown potential for the surface disinfection of fresh-cut fruit and vegetables. UV treatment of water (potable and wastewater) is increasingly common because the process is effective against a wide range of microorganisms, overdose is not possible, chemical residues or by-products are avoided, and water quality is unaffected. UV has been used to reduce the concentration of airborne microorganisms in limited studies, but the technology will require further development if it is to gain wider application. For bioaerosols, the primary technical challenge is delivery of sufficient UV irradiation to large volumes of air, but the absence of UV inactivation constants for airborne pathogens under a range of environmental conditions (temperature, relative humidity) further compounds the problem.

Reversible inactivation by cooling of the transcallosal projecting neurons in areas 17 and 18 of one hemisphere bring about complex changes in the spontaneous and evoked activity of neurons in the callosal receiving zone of the opposite hemisphere. These changes include increase and decreases in evoked and spotaneous activities. Overall, 90% of neurons in alyers II and III, 50% in layer IV, and 100% in layers V and VI were affected by the block of transcallosal input. The complexity of the changes was greatest in layers II and III, which are the major callosal recipient layers. The results indicate that many excitatory and inhibitory circuits are under the direct control of transcallosal fibers in the normally fuctioning brain.

Deactivation of light-activated squid rhodopsin was studied in vitro using GTPγS binding by G-protein as a direct measure of rhodopsin activity. Deactivation was inhibited by dilution of the retinal suspension or by removal of soluble components. Deactivation could be restored by addition of soluble material to washed membranes. These results indicate that the deactivation is not due entirely to a conformational transition within rhodopsin itself, but depends on the interaction with other molecules. The possibility that phosphorylation is involved in the deactivation was studied. Deactivation occurred in the presence and absence of added ATP. Deactivation also occurred in the presence of kinase inhibitors and after addition of apyrase, which reduced residual ATP levels to below 1μM. These results indicate that light-induced phosphorylation is not required for deactivation of squid rhodopsin. In this regard deactivation of squid rhodopsin is different from that of vertebrate rhodopsin, which requires phosphorylation.

We examined the functional properties of a low-voltage-activated (LVA) calcium current in ganglion cells of the neotenous tiger salamander (Ambystoma tigrinum) retina. Our analysis was based on whole-cell recordings from acutely dissociated ganglion cell bodies identified by retrograde dye injections. Using a continuously perfused cell preparation, the LVA current was isolated with the use of potassium channel blocking agents added to the bathing medium and the pipette solution, while tetrodotoxin was added to the bathing medium to block Na+ channels. Approximately 70% of ganglion cells had an easily identified LVA current. The LVA current activated at membrane potentials more positive than −90 mV, and inactivated rapidly. It was relatively insensitive to nickel (IC50 > 500 μM) and amiloride (IC50 > 750 μM). Voltage- and current-clamp studies allowed us to generate a model of this current using the NEURON simulation program. Studies were also carried out to measure the LVA Ca2+ current in ganglion cells with dendrites to confirm that it had a significant dendritic representation. Physiological mechanisms that may depend on LVA Ca2+ currents are discussed with an emphasis on the role that dendrites play in ganglion cell function.

Cryptosporidium are parasitic protozoans that cause gastrointestinal disease and represent a significant risk to public health. Cryptosporidium oocysts are prevalent in surface waters as a result of human, livestock and native animal faecal contamination. The resistance of oocysts to the concentrations of chlorine and monochloramine used to disinfect potable water increases the risk of waterborne transmission via drinking water. In addition to being resistant to commonly used disinfectants, it is thought that oocysts can persist in the environment and be readily mobilized by precipitation events. This paper will review the critical processes involved in the inactivation or removal of oocysts in the terrestrial and aquatic environments and consider how these processes will respond in the context of climate change.

The aspartic proteinase, chymosin (EC 3.4.23.4) is the principal milk clotting enzyme used in cheese production and is one of the principal proteolytic agents involved in cheese ripening. Varietal differences in chymosin activity, due to factors such as cheese cooking temperature, fundamentally influence cheese characteristics. Furthermore, much chymosin is lost in whey, and further processing of this by-product may require efficient inactivation of this enzyme, with minimal effects on whey proteins. In the first part of this study, the thermal inactivation kinetics of Maxiren 15 (a recombinant chymosin preparation) were studied in skim milk ultrafiltration permeate, whole milk whey and skim milk whey. Inactivation of chymosin in these systems (at pH 6.64) followed first order kinetics with a D45.5 value of 100±21 min and a z-value of 5.9±0.3 °C. D-Values increased linearly with decreasing pH from 6.64 to 6.2, while z-values decreased as pH decreased from 6.64 to 6.4, but were similar at pH 6.4 and 6.2. Subsequent determination of chymosin activity during manufacture of Cheddar and Swiss-type cheese showed good correlations between predicted and experimental values for thermal inactivation of chymosin in whey. However, both types of cheese curd exhibited relatively constant residual chymosin activity throughout manufacture, despite the higher cooking temperature applied in the manufacture of Swiss cheese. Electrophoretic analysis of slurries made from Cheddar and Swiss cheese indicated decreased proteolysis due to chymosin activity during storage of the Swiss cheese slurry, but hydrolysis of sodium caseinate by coagulant extracted from both cheese types indicated similar levels of residual chymosin activity. This may suggest that some form of conformational change other than irreversible thermal denaturation of chymisin takes place in cheese curd during cooking, or that some other physico-chemical difference between Swiss and Cheddar cheese controls the activity of chymosin during ripening.