Physiological and evolutionary studies of NAP systems in Shewanella piezotolerans WP3.

ABSTRACT: Most of the Shewanella species contain two periplasmic nitrate reductases (NAP-? and NAP-?), which is a unique feature of this genus. In the present study, the physiological function and evolutionary relationship of the two NAP systems were studied in the deep-sea bacterium Shewanella piezotolerans WP3. Both of the WP3 nap gene clusters: nap-? (napD1A1B1C) and nap-? (napD2A2B2) were shown to be involved in nitrate respiration. Phylogenetic analyses suggest that NAP-? originated earlier than NAP-?. Tetraheme cytochromes NapC and CymA were found to be the major electron deliver proteins, and CymA also served as a sole electron transporter towards nitrite reductase. Interestingly, a ?napA2 mutant with the single functional NAP-? system showed better growth than the wild-type strain, when grown in nitrate medium, and it had a selective advantage to the wild-type strain. On the basis of these results, we proposed the evolution direction of nitrate respiration system in Shewanella: from a single NAP-? to NAP-? and NAP-? both, followed by the evolution to a single NAP-?. Moreover, the data presented here will be very useful for the designed engineering of Shewanella for more efficient respiring capabilities for environmental bioremediation.

SUBMITTER: Chen Y 

PROVIDER: S-EPMC3105760 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature