Bacterial survival in response to desiccation and high humidity at above zero and subzero temperatures

Earthly microorganisms might have contaminated Mars for millions of years by intellectual activities or natural transfer. Knowledge on the preservation of microorganisms may help our searching for life on outer planets, particularly Mars-contaminated earthly microorganisms at ancient time. Extreme dryness is one of the current Mars characteristics. However, a humid or watery Mars at earlier time was suggested by evidence accumulated in recent decades. It raises the question that whether water helps preservation of the microorganisms or not, particularly those with high possibility of interplanetary transfer like spores and Deinococci. In this study, we examined the effects of desiccation and high humidity on survival and DNA double strand breaks (DSB) of Escherichia coli, Deinococcus radiodurans and spores of Bacillus pumilus at 25, 4 and −70 °C. They exhibited different survival rates and DSB patterns under desiccation and high humidity. Higher survival and less DSB occurred at lower temperature. We suggest that some Mars-contaminated bacteria might have been viably preserved on cold Mars regions for long periods, regardless of water availability. It is more likely to find ancient spores than ancient Deinococci on Mars. In our search for preserved extraterrestrial life, priority should be given to the Mars Polar Regions.     

Bacterial cellulose may provide the microbial-life biosignature in the rock records

Bacterial cellulose (BC) is a matrix for a biofilm formation, which is critical for survival and persistence of microbes in harsh environments. BC could play a significant role in the formation of microbial mats in pristine ecosystems on Earth. The prime objective of this study was to measure to what extent spectral and other characteristics of BC were changed under the performance of BC interaction with the earthly rock – anorthosite – via microorganisms. The spectral analyses (Fourier Transform Infrared FT-IR, spectroscopy, and atomic absorption spectroscopy) showed unprecedented accumulation of chemical elements in the BC-based biofilm. The absorption capacity of IR by BC was shielded a little by mineral crust formed by microorganisms on the BC-based biofilm surface, especially clearly seen in the range of 1200–900 cm⁻¹ in FT-IR spectra. Confocal scanning laser microscopy analysis revealed that elements bioleached from anorthosite created surface coats on the BC nanofibril web. At the same time, the vibrational spectra bands showed the presence of the characteristic region of anomeric carbons (960–730 cm⁻¹), wherein a band at 897 cm⁻¹ confirmed the presence of β-1, 4-linkages, which may serve as the cellulose fingerprint region. Results show that BC may be a biosignature for search signs of living organisms in rock records.     

Biological assessment of Ariane 5 fairing

United Nations Space Treaties [10 and 11] require the preservation of planets and of Earth from contamination. All nations part to these Treaties shall take measures to prevent forward and backward contamination during missions exploring our solar system. As observer for the United Nations Committee on Peaceful Uses of Outer Space, the COSPAR (Committee of Space Research) defines and handles the applicable policy and proposes recommendations to Space Agencies [COSPAR Planetary Protection Panel, Planetary Protection Policy accepted by the COSPAR Council and Bureau, 20 October 2002, amended 24 March 2005. http://www.cosparhq.org/scistr/PPPolicy.htm.]. The goal is to protect celestial bodies from terrestrial biological contamination as well as to protect the Earth environment from an eventual biohazard which may be carried by extraterrestrial samples or by space systems returning to Earth. According to the applicable specifications, including in our case the French requirements [CNES, System Safety. Planetary Protection Requirements. Normative referential CNES RNC-CNES-R-14, CNES Toulouse, ed. 4, 04 October 2002.], the prevention of forward contamination is accomplished by reducing the bioburden on space hardware to acceptable, prescribed levels, including in some instances system sterilization, assembling and integrating the appropriate spacecraft systems in cleanrooms of appropriate biological cleanliness, avoiding or controlling any recontamination risk, and limiting the probability impact of space systems. In order to prepare for future exploration missions [Debus, A., Planetary protection: organization requirements and needs for future planetary exploration missions, ESA conference publication SP-543, pp 103–114, 2003.], and in particular for missions to Mars requiring to control the spacecraft bioburden, a test program has been developed to evaluate the biological contamination under the fairing of the Ariane 5 launcher.     

Bioaugmentation in growing plants for lunar bases

Microorganisms may be a key element in a precursory scenario of growing pioneer plants for extraterrestrial exploration. They can be used for plant inoculation to leach nutritional elements from regolith, to alleviate lunar stressors, as well as to decompose both lunar rocks and the plant straw in order to form a protosoil. Bioleaching capacities of both French marigold (Tagetes patula L.) and the associated bacteria in contact with a lunar rock simulant (terrestrial anorthosite) were examined using the model plant-bacteria microcosms under controlled conditions. Marigold accumulated K, Na, Fe, Zn, Ni, and Cr at higher concentrations in anorthosite compared to the podzol soil. Plants inoculated with the consortium of well-defined species of bacteria accumulated higher levels of K, Mg, and Mn, but lower levels of Ni, Cr, Zn, Na, Ca, Fe, which exist at higher levels in anorthosite. Bacteria also affected the Са/Mg and Fe/Mn ratios in the biomass of marigold grown on anorthosite. Despite their growth retardation, the inoculated plants had 15% higher weight on anorthosite than noninoculated plants. The data suggest that the bacteria supplied basic macro-and microelements to the model plant.     

基于混合细菌觅食算法的多无人机任务分配研究

多无人机协同任务分配问题是多无人机协同控制的关键.本文首先深入分析多无人机任务分配问题的特点,建立了扩展的混合整数线性规划(MILP)任务分配模型.其次,通过分析细菌觅食优化算法和粒子群优化算法的优缺点,提出一种具有较强全局搜索能力且收敛速度快的混合细菌觅食优化算法.最后将该算法应用于多无人机协同任务分配中并进行了仿真...