title: Reduction of the temperature sensitivity of Halomonas hydrothermalis by iron starvation combined with microaerobic conditions.
abstract: The limits to biological processes on Earth are determined by physicochemical parameters, such as extremes of temperature and low water availability. Research into microbial extremophiles has enhanced our understanding of the biophysical boundaries which define the biosphere. However, there remains a paucity of information on the degree to which rates of microbial multiplication within extreme environments are determined by the availability of specific chemical elements. Here, we show that iron availability and the composition of the gaseous phase (aerobic versus microaerobic) determine the susceptibility of a marine bacterium, Halomonas hydrothermalis, to suboptimal and elevated temperature and salinity by impacting rates of cell division (but not viability). In particular, iron starvation combined with microaerobic conditions (5% [vol/vol] O2, 10% [vol/vol] CO2, reduced pH) reduced sensitivity to temperature across the 13°C range tested. These data demonstrate that nutrient limitation interacts with physicochemical parameters to determine biological permissiveness for extreme environments. The interplay between resource availability and stress tolerance, therefore, may shape the distribution and ecology of microorganisms within Earth's biosphere.
authors.affiliation: UK Centre for Astrobiology, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom j.p.harrison@ed.ac.uk.
authors.forename: Jesse P
authors.identifier: http://orcid.org/0000-0002-4877-4684
authors.initials: JP
authors.lastname: Harrison
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: John E
authors.initials: JE
authors.lastname: Hallsworth
authors.affiliation: UK Centre for Astrobiology, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cockell
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D020632:Halomonas / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D007501:Iron / Q000378:metabolism*; D050296:Microbial Viability / Q000528:radiation effects*; D054712:Salinity; D013696:Temperature
chemical_list: D007501:Iron