Autoflora in the upper respiratory tract of Apollo astronauts.

The typical microbial inhabitants of the oral and nasal cavities of Apollo astronauts were identified before space flight and generally found to be similar to those previously reported for healthy male adults. Additional analyses of samples collected immediately after return of the Apollo 13, 14, 15, and 16 crew members to earth were performed to evaluate the effects of space travel on the microbial bioburden of the upper respiratory tract. In-flight cross-contamination and buildup of pathogens such as Staphylococcus aureus were noted, although significant increases in nonpathogenic species were absent. Other proposed alterations, such as dysbacteriosis (flooding of the mouth with a single species) and simplification of the autoflora, did not occur. Generally, the incidence and quantitation of each species after flight was within the preflight range, although the number of viable Haemophilus cells recovered from the mouth decreased significantly after space flight. Except for those minor alterations listed above, the aerobic and anaerobic bacterial components of the upper respiratory autoflora of Apollo astronauts was found to be stable after space flight of up to 295 h.     

Antibiotic efficacy and microbial virulence during space flight

Human space flight is a complex undertaking that entails numerous technological and biomedical challenges. Engineers and scientists endeavor, to the extent possible, to identify and mitigate the ensuing risks. The potential for an outbreak of an infectious disease in a spacecraft presents one such concern, which is compounded by several components unique to an extraterrestrial environment. Various factors associated with the space flight environment have been shown to potentially compromise the immune system of astronauts, increase microbial proliferation and microflora exchange, alter virulence and decrease antibiotic effectiveness. An acceptable resolution of the above concerns must be achieved to ensure safe and efficient space habitation. To help bring this about, scientists are employing advances in biotechnology to better characterize the relevant variables and establish appropriate solutions. Because many of these clinical concerns are also relevant in terrestrial society, this research will have reciprocal benefits back on Earth.     

Considerations for non-invasive in-flight monitoring of astronaut immune status with potential use of MEMS and NEMS devices

The dynamics of how astronauts' immune systems respond to space flight have been studied extensively, but the complex process has not to date been thoroughly characterized, nor have the underlying principles of what causes the immune system to change in microgravity been fully determined. Statistically significant results regarding overall immunological effects in space have not yet been established due to the relatively limited amount of experimental data available, and are further complicated by the findings not showing systematically reproducible trends. Collecting in vivo data during flight without affecting the system being measured would increase understanding of the immune response process.The aims of this paper are to briefly review the current knowledge regarding how the immune system is altered in space flight; to present a group of candidate biomarkers that could be useful for in-flight monitoring and give an overview of the current methods used to measure these markers; and finally, to further establish the need and usefulness of incorporating real-time analytical techniques for in-flight assessment of astronaut health, emphasizing the potential application of MEMS/NEMS devices.     

Stress, suspension and resistance to infection

Immune function is altered in stressful situations, including space flight. This may result in increased risk of infection. Antiorthostatic suspension has been used to study the effects of space flight-like conditions on immunity. The mechanisms of promoting infection in stressful situations have not been defined, but catecholamines could play a role. In the present study gram negative bacteria grown with catecholamines showed enhanced bacterial growth compared to controls. Additionally, antiorthostatically suspended mice infected with Klebsiella pneumoniae showed decreased survival compared to restrained or normally caged controls. Therefore, stress-induced enhanced bacterial growth and immunosuppression could play a role in suspension-induced enhanced mortality due to infection.     

Quantitative studies of bacterial chemotaxis and microbial population dynamics

Although there is a long history of conjecture regarding the role and significance of bacterial chemotaxis in microbial ecology, only recently has a significant body of work appeared attempting to address this issue. The purpose of this paper is to provide a concise overview of this work, which combined mathematical modeling of bacterial population migration and experimental measurement of the model parameters with modeling of competitive microbial population dynamics in a nonmixed environment. Predictions from the population dynamics models, based on experimental estimates of the various motility and growth parameter values, are related to the small number of experimental observations available to date dealing with the effects of bacterial motility on competition in a nonmixed environment. Current results indicate that cell motility and chemotaxis properties can be as important to population dynamics as cell growth kinetic properties, so that greater attention to this aspect of microbial behavior is warranted in future studies of microbial ecology.     

Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.     

Microbial antibiotic production aboard the International Space Station

Previous studies examining metabolic characteristics of bacterial cultures have mostly suggested that reduced gravity is advantageous for microbial growth. As a consequence, the question of whether space flight would similarly enhance secondary metabolite production was raised. Results from three prior space shuttle experiments indicated that antibiotic production was stimulated in space for two different microbial systems, albeit under suboptimal growth conditions. The goal of this latest experiment was to determine whether the enhanced productivity would also occur with better growth conditions and over longer durations of weightlessness. Microbial antibiotic production was examined onboard the International Space Station during the 72-day 8A increment. Findings of increased productivity of actinomycin D by Streptomyces plicatus in space corroborated with previous findings for the early sample points (days 8 and 12); however, the flight production levels were lower than the matched ground control samples for the remainder of the mission. The overall goal of this research program is to elucidate the specific mechanisms responsible for the initial stimulation of productivity in space and translate this knowledge into methods for improving efficiency of commercial production facilities on Earth.     

Polysaccharases for microbial exopolysaccharides

Microbial exopolysaccharides (EPS) are the substrates for a wide range of enzymes most of which are highly specific. The enzymes are either endoglycanases or polysaccharide lyases and their specificity is determined by carbohydrate structure with uronic acids often playing a major role. The presence of various acyl substituents frequently has little effect on the action of many of the polysaccharases but markedly inhibits some of the polysaccharide lyases including alginate and gellan lyases. The commonest sources of such enzymes can be either microorganisms or bacteriophages. These specific polysaccharide-degrading enzymes can yield oligosaccharide fragments, which are amenable to NMR and other analytical techniques. They have thus proved to be extremely useful in providing information about microbial polysaccharide structures and were routinely used in many such studies. Complex systems containing various mixtures of enzymes may also be effective in the absence of single enzymes but may be difficult to obtain with reproducible activities. Such preparations may also cause extensive degradation of the polysaccharide structure and thus prove less useful in providing information. Commercially available enzyme preparations have seldom proved capable of degrading microbial heteropolysaccharides, although some are active against bacterial alginates and homopolysaccharides including bacterial cellulose and curdlan.     

Secondary metabolism in simulated microgravity and space flight

Space flight experiments have suggested that microgravity can affect cellular processes in microorganisms. To simulate the microgravity environment on earth, several models have been developed and applied to examine the effect of microgravity on secondary metabolism. In this paper, studies of effects of space flight on secondary metabolism are exemplified and reviewed along with the advantages and disadvantages of the current models used for simulating microgravity. This discussion is both signi?cant and timely to researchers considering the use of simulated microgravity or space flight to explore effects of weightlessness on secondary metabolism.     

Management of biofilm-associated infections: what can we expect from recent research on biofilm lifestyles?

Biofilms are surface-associated microbial communities present in all environments. Although biofilms play important ecological roles, they also lead to negative or deleterious effects in industrial and medical settings. In the latter, high levels of antibiotic tolerance of bacterial biofilms developing on medical devices and during chronic infections determine the physiopathology of many healthcare-associated infections. Original approaches have been developed to avoid bacterial adhesion or biofilm development targetting specific mechanisms or pathways. We herein review recent data about biofilm lifestyle understanding and ways to fight against related infections.     

Targets and assays for discovering novel antibacterial agents

The increasing frequency of nosocomial infections due to multi-resistant pathogens exerts a significant toll and calls for novel and better antibiotics. Different approaches can be used in the search for novel antibiotics acting on drug-resistant bacterial pathogens. We present some considerations on valid bacterial targets to be used for searching new antibiotics, and how the information from bacterial genome sequences can assist in choosing the appropriate targets. Other factors to be considered in target selection are the chemical diversity available for screening and its uniqueness. We will conclude discussing our strategy for searching novel antibacterials. This is based on a large collection of microbial extracts as a source of chemical diversity and on the use of specific targets essential for the viability of bacterial pathogens. Two assay strategies have been implemented: a pathway-based assay, where a series of essential bacterial targets is screened in a single assay; and a binding assay, where many targets can be screened individually in the same format.     

Population and community level approaches for analysing microbial diversity in natural environments

The enormous diversity available at the microbial level is just beginning to be realized. The richness of diversity amongst the bacteria that have been described so far is between 2 and 3000, whereas estimates indicates that millions of microorganisms still remains to be discovered. Microbiologists have realized that there are at least a dozen major evolutionary groups of the microbial life forms on earth (bacteria, fungi, algae and protozoa) that are even more diverse than the better known animal and plant kingdom. Indeed, we can state that microorganisms dominate the tree of life. Microorganisms have inhabited Earth for more than 3.7 billion years, whereas plants and animals have evolved rather recently in Earth's history. Possible reports of evidence for microbial life on Mars is also consistent with the concept that microorganisms precede plants and animals on Earth. The applications of molecular-phylogenetic techniques have provided the tools for studying natural microbial communities, including those that we are not able to grow in the laboratory. The utilization of these techniques has resulted in the discovery of many new evolutionary lineages, some of them only distantly related to known organisms. Here I discuss some environmental factors controlling bacterial diversity in different environments and the utility of modern methods developed for describing this diversity.     

Engineering issues of microbial ecology in space agriculture]

Closure of the materials recycle loop for water-foods-oxygen is the primary purpose of space agriculture on Mars and Moon. A microbial ecological system takes a part of agriculture to process our metabolic excreta and inedible biomass and convert them to nutrients and soil substrate for cultivating plants. If we extend the purpose of space agriculture to the creation and control of a healthy and pleasant living environment, we should realize that our human body should not be sterilized but exposed to the appropriate microbial environment. We are proposing a use of hyper-thermophilic aerobic composting microbial ecology in space agriculture. Japan has a broad historical and cultural background on this subject. There had been agriculture that drove a closed loop of materials between consuming cities and farming villages in vicinity. Recent environmental problems regarding garbage collection and processing in towns have motivated home electronics companies to innovate "garbage composting" machines with bacterial technology. Based on those matured technology, together with new insights on microbiology and microbial ecology, we have been developing a conceptual design of space agriculture on Moon and Mars. There are several issues to be answered in order to prove effectiveness of the use of microbial systems in space. 1) Can the recycled nutrients, processed by the hyper-thermal aerobic composting microbial ecology, be formed in the physical and chemical state or configuration, with which plants can uptake those nutrients? A possibility of removing any major components of fertilizer from its recycle loop is another item to be evaluated. 2) What are the merits of forming soil microbial ecology around the root system of plants? This might be the most crucial question. Recent researches exhibit various mutually beneficial relationships among soil microbiota and plants, and symbiotic ecology in composting bacteria. It is essential to understand those features, and define how to conduct preventive maintenance for keeping cultivating soil healthy and productive. 3) Does microbial ecology contribute to building sustainable and expandable human habitation by utilizing the on site extraterrestrial resources? We are assessing technical feasibility of converting regolith to farming soil and structural materials for space agriculture. In the case of Mars habitation, carbon dioxide and a trace amount of nitrogen in atmosphere, and potassium and phosphor in minerals are the sources we consider. Excess oxygen can be accumulated by woods cultivation and their use for lumber. 4) Is the operation of space agriculture robust and safe, if it adopts hyper-thermophilic aerobic microbial ecology? Any ecological system is complex and non-linear, and shows latency and memory effects in its response. It is highly important to understand those features to design and operate space agriculture without falling into the fatal failure. Assessment should be made on the microbial safety and preparation of the preventive measures to eliminate negative elements that would either retard agricultural production or harm the healthy environment. It is worth to mention that such space agriculture would be an effective engineering testbed to solve the global problem on energy and environment. Mars and Moon exploration itself is a good advocate of healthy curiosity expressed by the sustainable civilization of our humankind. We propose to work together towards Mars and Moon with microbial ecology to assure pleasant habitation there.     

A field test of commercial soil microbial treatments on native grassland restoration

Seedling establishment and performance are often limiting steps in many grassland restorations. The soil microbial community is thought to be a factor that contributes to the poor performance of seedlings. Therefore, we conducted a field test to examine the ability of four treatments to alter the soil microbial community and improve seedling performance during restoration. Treatments were commercially available bacterial inoculum, fungal inoculum, fungicide, and a bacteria/fungicide combination which were all designed and sold to enhance plant performance. We hypothesized that if the soil microbial community was limiting the performance of seedlings, then these products would remediate detrimental effects of the soil microbial community resulting in greater seedling performance. However, during the 2 years after restoration, no effect of the treatments was found. It is plausible that the treatments designed for agriculture or home garden settings were not appropriate for a wildland system.     

β-Lactam and glycopeptide antibiotics: first and last line of defense?

Most infections are caused by bacteria, many of which are ever-evolving and resistant to nearly all available antibiotics. β-Lactams and glycopeptides are used to combat these infections by inhibiting bacterial cell-wall synthesis. This mechanism remains an interesting target in the search for new antibiotics in light of failed genomic approaches and the limited input of major pharmaceutical companies. Several strategies have enriched the pipeline of bacterial cell-wall inhibitors; examples include combining screening strategies with lesser-explored microbial diversity, or reinventing known scaffolds based on structure-function relationships. Drugs developed using novel strategies will contribute to the arsenal in fight against the continued emergence of bacterial resistance.     

Expanding the known diversity and environmental distribution of cultured and uncultured bacteria

Microorganisms represent the largest component of biodiversity in our biosphere. Traditional methods of bacterial identification depend on their culture on laboratory media and the comparison of their phenotypic characteristics. They include cellular morphology, motility, staining reactions of cell walls, ability to grow on different media and biochemical tests. These methods have many limitations and only a very small fraction of microorganisms have been cultivated. To date, molecular methods based on 16S rRNA sequences and their phylogenetic analysis are widely used for reliable identification, particularly for hard-to-culture microbial pathogens. These so-called < molecular methods > do not require laboratory culture of isolated organisms, and many novel non-described phyla have been detected, improving our view of bacterial diversity. Novel strategies for culturing the < uncultivated > are now under development, which are leading to the complete characterization of these new bacteria. More recently, meta- or ecogenomics, based on the complete sequencing of clones containing cosmids or bacterial artificial chromosomes with inserts, addresses the genetic potential of a sample irrespective of whether the microorganisms can be cultured or not. This has considerably extended our view of microbial diversity at the genomic level and the probability of finding new genes and their products suitable for the biotechnological and pharmaceutical industry.     

Germanium and silver resistance, accumulation, and toxicity in microorganisms.

Germanium is an inert metal with no known biological function in prokaryotic or eukaryotic organisms. Its toxicity is low compared to that of silver. Germanium is accumulated in certain bacterial strains by either energy-independent passive binding or an energy-dependent mechanism. Little is known about the molecular aspects of silver resistance, toxicity, and accumulation in bacterial strains. This is surprising because silver has been used as an antimicrobial agent in the medical field for centuries. It is likely that silver ions are excluded (resulting in decreased silver accumulation) from certain bacterial strains or immobilized intracellularly to prevent toxic effects from being exerted. These mechanisms of silver resistance have not been fully elucidated. This review examines the toxicity and accumulation of germanium and silver in selected microbial species. In addition, resistance mechanisms to these biologically nonessential metals is discussed, with more emphasis placed on silver-resistant bacteria due to the knowledge available.     

Effects of clinostat-microgravity on bone and calcium metabolism in rats

Decreases in bone minerals and tissue volume after space flight have been observed in humans and animals, with a variety of results. Such data obtained from space flight experiments have given unsatisfactory results due to short periods of space flight and differences in age, body weights, and strain of animals used. Therefore, ground-based animal models have been developed in order to elucidate changes in bone affected by space flight. For example, a tail-suspended rat model has been established to study the effects of microgravity on bones by producing hind limb unloading. However, problems with this model due to the remaining forelimb loading and the unusual changes in blood current require the development of a new model simulating the physiological conditions of space flight. So we developed a three-dimension clinostat as an apparatus to produce a simulated microgravity similar to space flight by rotating rats equally in all directions. The purpose of the present study is to examine the effects of clinostat-microgravity on bone metabolism in rats.     

Simulated microgravity (SMG) and bacteria.

This past century has been a scientific revolution in the understanding of the cell as the basic unit of life. However an immense paucity of knowledge exists on microbial growth, survival, function and structure in space. However, there are significant constraints placed on conducting biological research in space such as time, available stowage space, trained personnel, power requirements, weight and the possibility of accidental microbiological contamination. One Earth-based approach is to use a modification of a clinostat known as a HARV (high-aspect-ratio-vessel; Synthecon Inc., Houston, Texas, USA) to conduct this research. In this note we describe the use of the HARV to examine the effects of randomized microgravity (RMG) on bacterial growth and membrane polarization.