Characterization of the survival ability of Cupriavidus metallidurans and Ralstonia pickettii from space-related environments.

Four Cupriavidus metallidurans and eight Ralstonia pickettii isolates from the space industry and the International Space Station (ISS) were characterized in detail. Nine of the 12 isolates were able to form a biofilm on plastics and all were resistant to several antibiotics. R. pickettii isolates from the surface of the Mars Orbiter prior to flight were 2.5 times more resistant to UV-C(254nm) radiation compared to the R. pickettii type strain. All isolates showed moderate to high tolerance against at least seven different metal ions. They were tolerant to medium to high silver concentrations (0.5-4 µM), which are higher than the ionic silver disinfectant concentrations measured regularly in the drinking water aboard the ISS. Furthermore, all isolates survived a 23-month exposure to 2 µM AgNO(3) in drinking water. These resistance properties are putatively encoded by their endogenous megaplasmids. This study demonstrated that extreme resistance is not required to withstand the disinfection and sterilization procedures implemented in the ISS and space industry. All isolates acquired moderate to high tolerance against several stressors and can grow in oligotrophic conditions, enabling them to persist in these environments.

Microarray analysis of a microbe-mineral interaction.

The weathering of volcanic minerals makes a significant contribution to the global silicate weathering budget, influencing carbon dioxide drawdown and long-term climate control. Basalt rocks may account for over 30% of the global carbon dioxide drawdown in silicate weathering. Micro-organisms are known to play a role in rock weathering yet the genomics and genetics of biological rock weathering are unknown. We apply DNA microarray technology to determine putative genes involved in weathering using the heavy metal-resistant organism, Cupriavidus metallidurans CH34; in particular we investigate the sequestering of iron. The results show that the bacterium does not depend on siderophores. Instead, the up-regulation of porins and transporters which are employed concomitantly with genes associated with biofilm formation suggests that novel passive and active iron uptake systems are involved. We hypothesize that these mechanisms induce rock weathering by changes in chemical equilibrium at the microbe-mineral interface, reducing the saturation state of iron. We also demonstrate that low concentrations of metals in the basalt induce heavy metal-resistant genes. Some of the earliest environments on the Earth were volcanic. Therefore, these results not only elucidate the mechanisms by which micro-organisms might have sequestered nutrients on the early Earth but also provide an explanation for the evolution of multiple heavy metal resistance genes long before the creation of contaminated industrial biotopes by human activity.

Genome sequence of the edible cyanobacterium Arthrospira sp. PCC 8005.

We determined the genome sequence of Arthrospira sp. PCC 8005, a cyanobacterial strain of great interest to the European Space Agency for its nutritive value and oxygenic properties in the Micro-Ecological Life Support System Alternative (MELiSSA) biological life support system for long-term manned missions into space.

Radiation dosimetry for microbial experiments in the International Space Station using different etched track and luminescent detectors.

The laboratory of Microbiology at SCK.CEN, in collaboration with different universities, participates in several ESA programmes with bacterial experiments that are carried out in the International Space Station (ISS). The main objective of these programmes is to study the effects of space flight conditions such as microgravity and cosmic radiation on the general behaviour of model bacteria. To measure the radiation doses received by the bacteria, different detectors accompanied the microbiological experiments. The results obtained during two space flight missions are discussed. This dosimetry experiment was a collaboration between different institutes so that the doses could be estimated by different techniques. For measurement of the high linear energy transfer (LET) doses (>10 keV microm(-1)), two types of etched track detectors were used. The low LET part of the spectrum was measured by three types of thermoluminescent detectors ((7)LiF:Mg,Ti; (7)LiF:Mg,Cu,P; Al(2)O(3):C) and by the optically stimulated luminescence technique using Al(2)O(3):C detectors.

Culture independent detection of Sphingomonas sp. EPA 505 related strains in soils contaminated with polycyclic aromatic hydrocarbons (PAHs).

The Sphingomonas genus hosts many interesting pollutant-degrading strains. Sphingomonas sp. EPA505 is the best studied polycyclic aromatic hydrocarbon (PAH)-degrading Sphingomonas strain. Based on 16S rRNA gene sequence analysis, Sphingomonas sp. strain EPA505 forms a separate branch in the Sphingomonas phylogenetic tree grouping exclusively PAH-degrading isolates. For specific PCR detection and monitoring of Sphingomonas sp. EPA505 and related strains in PAH-contaminated soils, a new 16S rRNA gene-based primer set was designed. The new primer set was shown to be highly selective for Sphingomonas sp. strain EPA505 as it only amplified DNA from strain EPA505 and not from other tested Sphingomonas strains or soil bacteria not belonging to the Sphingomonas genus. Using DNA extracts of a variety of inoculated PAH-contaminated soils, the primer pair was able to detect EPA505 in concentrations as low as 10(2) cells per gram of soil. Applying the new primer set, 16S rRNA gene fragments which were 99-100% similar to the corresponding gene of strain EPA505 were amplified from four of five PAH-contaminated soils. On the other hand, no PCR products were obtained from any of five tested uncontaminated soils. The preferential presence of EPA505 related Sphingomonas strains in PAH-contaminated soils with very different contamination profiles and different origin suggests an important role of this type of Sphingomonas in the natural Sphingomonas community colonizing PAH-contaminated sites.

Space flight effects on bacterial physiology.

The study of bacterial behavior under space flight conditions is highly important for the early detection of changes in bacterial communities and bacteria with medical, environmental, or life support consequences for survival of the crew in closed space environments. Although many species of prokaryotes have been studied in ground simulation facilities or have been flown in space flights, at present only few hard research data are available to predict the effects of cosmic radiation, microgravity, vibration and hypervelocity on microbial behavior in space flight. The results that are available tend to be fragmentary and often lack a classical, controlled experimental context to interpret them. Thus, many basic questions concerning the effects of space on microbial behavior have yet to be resolved.