The limits to genomic predictions: role of sigma(N) in environmental stress survival of Pseudomonas putida

Based on genomic data and on the phenotypes of an FlhF mutant of Pseudomona s putida, the alternative sigma factor sigma (N) (sigma (54)) has been prop osed to play a key role in survival to various nutritional and environmenta l stresses in this bacterium. Quite in contrast, we show that unlike sigma (S) (sigma (38)) the loss of sigma (N) does not impair to any significant e xtent the ability of P. putida to survive long-term starvation. rpoN mutant s (lacking sigma (N)) al e indistinguishable from the wild-type with respec t to solvent tolerance. resistance to heat shock or sensitivity to hydrogen peroxide. These data suggest that while sigma (N) is a key component of ex pression of alternative biodegradative pathways for unusual carbon sources (i.e,, m-xylene or dimethylphenols), its loss does not compromise bacterial endurance to gross types of environmental stress. Moreover, these results point out the limitations, if not the deception. of genomic predictions the n confronted with experimental data. (C) 2001 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights reserved .