Abstract
The arid Mojave Desert is one of the most significant terrestrial analogue objects for astrobiological research due to its genesis, mineralogy, and climate. However, the knowledge of culturable bacterial communities found in this extreme ecotope’s soil is yet insufficient. Therefore, our research has been aimed to fulfil this lack of knowledge and improve the understanding of functioning of edaphic bacterial communities of the Central Mojave Desert soil. We characterized aerobic heterotrophic soil bacterial communities of the central region of the Mojave Desert. A high total number of prokaryotic cells and a high proportion of culturable forms in the soil studied were observed. Prevalence of Actinobacteria, Proteobacteria, and Firmicutes was discovered. The dominance of pigmented strains in culturable communities and high proportion of thermotolerant and pH-tolerant bacteria were detected. Resistance to a number of salts, including the ones found in Martian regolith, as well as antibiotic resistance, were also estimated.
Highlights
One of the main tasks of modern astrobiology is studying environmental factors of different space bodies and outer space and to determine surviving and functioning limits of terrestrial life forms under extraterrestrial conditions [1,2].It is known that potentially habitable space objects are exposed to a number of extreme abiotic factors, including high-intensity ionizing radiation, reduced pressure, contrast temperature conditions, low water availability, etc. [3,4,5]
We studied the aerobic heterotrophic bacterial community and the physiological characteristics of cultured bacteria, isolated from the surface soil sample collected in the central part of the Mojave Desert
We have not found any previously published data on antibiotic resistance of representatives of Planomicrobium, Salinibacterium, and Labedella genera. Stress effects, such as low water availability, nutrients deficiencies, high levels of solar radiation, and wide temperature fluctuations in the surface soil of the Mojave Desert lead to the formation of physiological survival strategies for prokaryotes existing under these conditions [2,3]
Summary
One of the main tasks of modern astrobiology is studying environmental factors of different space bodies and outer space and to determine surviving and functioning limits of terrestrial life forms under extraterrestrial conditions [1,2].It is known that potentially habitable space objects are exposed to a number of extreme abiotic factors, including high-intensity ionizing radiation, reduced pressure, contrast temperature conditions, low water availability, etc. [3,4,5]. A large amount of data on physicochemical properties of regolith and climatic and cosmic regimes of various extraterrestrial bodies, in particular Mars, have been accumulated [6]. Microorganisms of arid ecosystems are exposed to a wide spectrum of stress factors such as water and organic matter deficiency, exposure to winds and high-intensity ultraviolet (UV) radiation, and significant temperature fluctuations. These areas are not lifeless and are characterized by Geosciences 2019, 9, 166; doi:10.3390/geosciences9040166 www.mdpi.com/journal/geosciences
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