Abstract
The effect of Bacillus subtilis exposure to the human spaceflight environment on growth, mutagenic frequency, and spectrum of mutations to rifampicin resistance (RifR) was investigated. B. subtilis cells were cultivated in Biological Research in Canister-Petri Dish Fixation Units (BRIC-PDFUs) on two separate missions to the International Space Station (ISS), dubbed BRIC-18 and BRIC-21, with matching asynchronous ground controls. No statistically significant difference in either growth or in the frequency of mutation to RifR was found in either experiment. However, nucleotide sequencing of the RifR regions of the rpoB gene from RifR mutants revealed dramatic differences in the spectrum of mutations between flight (FL) and ground control (GC) samples, including two newly discovered rpoB alleles in the FL samples (Q137R and L489S). The results strengthen the idea that exposure to the human spaceflight environment causes unique stresses on bacteria, leading to alterations in their mutagenic potential.
Highlights
In contrast to the classical view that mutations are random, a growing body of evidence indicates that exposure to environmental stresses in microbes can alter both the mutation rate and the mutagenic spectrum, supplying an increased variety of mutational outputs for selection to operate on and shaping the evolutionary trajectory of organisms (Nicholson and Maughan, 2002; Foster, 2007; Nicholson and Park, 2015; Maharjan and Ferenci, 2017b)
Exert longer-range effects by distorting the binding pocket out of its optimum shape (Severinov et al, 1994). In this communication we describe the results of two spaceflight experiments using B. subtilis in which growth, the frequency of Growth in FL vs ground control (GC) Samples
A number of experiments have been conducted in which various bacterial species have been cultivated under otherwisematching conditions of hardware, media, inoculation, etc., and their growth, as measured by final cell density, has been compared in spaceflight vs. ground control samples
Summary
In contrast to the classical view that mutations are random, a growing body of evidence indicates that exposure to environmental stresses in microbes can alter both the mutation rate and the mutagenic spectrum, supplying an increased variety of mutational outputs for selection to operate on and shaping the evolutionary trajectory of organisms (Nicholson and Maughan, 2002; Foster, 2007; Nicholson and Park, 2015; Maharjan and Ferenci, 2017b).
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