Growth at 5 kPa Causes Differential Expression of a Number of Signals in a Strain Adapted to Enhanced Growth at Low Pressure.

To determine microbial evolutionary strategies to low-pressure (LP; 5 kPa) growth, an environmental condition not experienced on Earth until ∼20 km in altitude, a previously described evolutionary experiment was conducted. The resulting LP evolved strain WN1106, isolated from the terminus of the experiment, was shown to have several genomic mutations absent in the ancestral strain, WN624. Three of the mutations were in regulatory genes: , , and .

MARSBOx: Fungal and Bacterial Endurance From a Balloon-Flown Analog Mission in the Stratosphere.

Whether terrestrial life can withstand the martian environment is of paramount interest for planetary protection measures and space exploration. To understand microbial survival potential in Mars-like conditions, several fungal and bacterial samples were launched in September 2019 on a large NASA scientific balloon flight to the middle stratosphere (∼38 km altitude) where radiation levels resembled values at the equatorial Mars surface. Fungal spores of and bacterial cells of , subsp.

Sierra Nevada sweep: metagenomic measurements of bioaerosols vertically distributed across the troposphere.

To explore how airborne microbial patterns change with height above the Earth's surface, we flew NASA's C-20A aircraft on two consecutive days in June 2018 along identical flight paths over the US Sierra Nevada mountain range at four different altitudes ranging from 10,000 ft to 40,000 ft. Bioaerosols were analyzed by metagenomic DNA sequencing and traditional culturing methods to characterize the composition and diversity of atmospheric samples compared to experimental controls. The relative abundance of taxa changed significantly at each altitude sampled, and the diversity profile shifted across the two sampling days, revealing a regional atmospheric microbiome that is dynamically changing.

Metagenomic investigation of African dust events in the Caribbean.

African dust from the Sahara and Sahel regions of Northern Africa is blown intercontinental distances and is the highest portion of atmospheric dust generated each year. During the Northern Hemisphere summer months (boreal summer), these dust events travel into the Caribbean and southern United States. While viability assays, microscopy and bacterial amplicon analyses have shown that dust-associated microbes may be diverse, the specific microbial taxa that are transported intercontinental distances with these dust events remain poorly characterized.

Experimental evolution of enhanced growth by Bacillus subtilis at low atmospheric pressure: genomic changes revealed by whole-genome sequencing.

Knowledge of how microorganisms respond and adapt to low-pressure (LP) environments is limited. Previously, Bacillus subtilis strain WN624 was grown at the near-inhibitory LP of 5 kPa for 1,000 generations and strain WN1106, which exhibited increased relative fitness at 5 kPa, was isolated. Genomic sequence differences between ancestral strain WN624 and LP-evolved strain WN1106 were identified using whole-genome sequencing.

Exposure of Bacillus subtilis to low pressure (5 kilopascals) induces several global regulons, including those involved in the SigB-mediated general stress response.

Studies of how microorganisms respond to pressure have been limited mostly to the extreme high pressures of the deep sea (i.e., the piezosphere).

Evolution of Bacillus subtilis to enhanced growth at low pressure: up-regulated transcription of des-desKR, encoding the fatty acid desaturase system.

The atmospheric pressure on Mars ranges from 1-10 mbar, about 1% of Earth pressure (∼1013 mbar). Low pressure is a growth-inhibitory factor for terrestrial microorganisms on Mars, and a putative low-pressure barrier for growth of Earth bacteria of ∼25 mbar has been postulated. In a previous communication, we described the isolation of a strain of Bacillus subtilis that had evolved enhanced growth ability at the near-inhibitory low pressure of 50 mbar.

Exploring the low-pressure growth limit: evolution of Bacillus subtilis in the laboratory to enhanced growth at 5 kilopascals.

Growth of Bacillus subtilis cells, normally adapted at Earth-normal atmospheric pressure (∼101.3 kPa), was progressively inhibited by lowering of pressure in liquid LB medium until growth essentially ceased at 2.5 kPa.