title: Contrasted resistance of stone-dwelling Geodermatophilaceae species to stresses known to give rise to reactive oxygen species.
abstract: Stones in arid environments are inhabited by actinobacteria of the family Geodermatophilaceae like the genera Blastococcus and Modestobacter frequently isolated from altered calcarenites. Their habitat requires adaptation to light-induced and other stresses that generate reactive oxygen species. Here, we show that representative members of the species Blastococcus saxobsidens, Geodermatophilus obscurus, and Modestobacter multiseptatus are differentially adapted to stresses associated with arid environments. Whereas B. saxobsidens was found to be sensitive to gamma radiation (D(10)  = 900 Gy; 10% survival at 900 Gy), M. multiseptatus was moderately (D(10)  = 6000 Gy) and G. obscurus was highly tolerant (D(10)  = 9000 Gy). A difference in resistance to high-frequency (λ value = 254 nm) UV was shown by B. saxobsidens, M. multiseptatus, and G. obscurus, being sensitive, tolerant, and highly tolerant (D(10)  of 6, 900, and > 3500 kJ m(-2) , respectively). Tolerance to desiccation, mitomycin C and hydrogen peroxide correlated with the ionizing radiation and UV resistance profiles of the three species and were correlated with the pigments synthesized. Resistance to heavy metals/metalloids did not follow the same pattern, with resistance to Ag(2+)  and Pb(2+)  being similar for B. saxobsidens, M. multiseptatus, and G. obscurus, whereas resistance to AsO4 3-, Cr(2+) , or Cu(2+)  was greater for B. saxobsidens than for the other two species. The stress resistance profiles of M. multiseptatus and B. saxobsidens were reflected in different calcarenite colonization patterns. While M. multiseptatus was predominantly isolated from the first two millimeters of stone surface, B. saxobsidens was predominantly isolated from the deeper part of the stone where it is better protected from sun irradiation, suggesting that the response to light- and desiccation-induced oxidative stress is an important driver for niche colonization in the stone biotope.
authors.affiliation: Laboratoire Microorganismes et Biomolécules Actives, Université de Tunis Elmanar (FST) et Université de Carthage (ISSTE), Tunis, Tunisia. maher.gtari@fst.rnu.tn
authors.forename: Maher
authors.initials: M
authors.lastname: Gtari
authors.forename: Imen
authors.initials: I
authors.lastname: Essoussi
authors.forename: Radhi
authors.initials: R
authors.lastname: Maaoui
authors.forename: Haïtham
authors.initials: H
authors.lastname: Sghaier
authors.forename: Rabeb
authors.initials: R
authors.lastname: Boujmil
authors.forename: Jérôme
authors.initials: J
authors.lastname: Gury
authors.forename: Petar
authors.initials: P
authors.lastname: Pujic
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Brusetti
authors.forename: Bessem
authors.initials: B
authors.lastname: Chouaia
authors.forename: Elena
authors.initials: E
authors.lastname: Crotti
authors.forename: Daniele
authors.initials: D
authors.lastname: Daffonchio
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Boudabous
authors.forename: Philippe
authors.initials: P
authors.lastname: Normand
mesh_terms: D000192:Actinomycetales / Q000302:isolation & purification / Q000502:physiology* / Q000528:radiation effects; D003681:Dehydration; D017753:Ecosystem; D005720:Gamma Rays; D019083:Mediterranean Region; D019216:Metals, Heavy / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012988:Soil Microbiology; D013312:Stress, Physiological; D014466:Ultraviolet Rays
chemical_list: D019216:Metals, Heavy; D017382:Reactive Oxygen Species