In:
Journal of Bacteriology, American Society for Microbiology, Vol. 197, No. 19 ( 2015-10), p. 3160-3172
Abstract:
The ubiquitous aquatic bacterium Caulobacter crescentus is highly resistant to uranium (U) and facilitates U biomineralization and thus holds promise as an agent of U bioremediation. To gain an understanding of how C. crescentus tolerates U, we employed transposon (Tn) mutagenesis paired with deep sequencing (Tn-seq) in a global screen for genomic elements required for U resistance. Of the 3,879 annotated genes in the C. crescentus genome, 37 were found to be specifically associated with fitness under U stress, 15 of which were subsequently tested through mutational analysis. Systematic deletion analysis revealed that mutants lacking outer membrane transporters ( rsaF a and rsaF b ), a stress-responsive transcription factor ( cztR ), or a ppGpp synthetase/hydrolase ( spoT ) exhibited a significantly lower survival rate under U stress. RsaF a and RsaF b , which are homologues of TolC in Escherichia coli , have previously been shown to mediate S-layer export. Transcriptional analysis revealed upregulation of rsaF a and rsaF b by 4- and 10-fold, respectively, in the presence of U. We additionally show that rsaF a mutants accumulated higher levels of U than the wild type, with no significant increase in oxidative stress levels. Our results suggest a function for RsaF a and RsaF b in U efflux and/or maintenance of membrane integrity during U stress. In addition, we present data implicating CztR and SpoT in resistance to U stress. Together, our findings reveal novel gene targets that are key to understanding the molecular mechanisms of U resistance in C. crescentus . IMPORTANCE Caulobacter crescentus is an aerobic bacterium that is highly resistant to uranium (U) and has great potential to be used in U bioremediation, but its mechanisms of U resistance are poorly understood. We conducted a Tn-seq screen to identify genes specifically required for U resistance in C. crescentus . The genes that we identified have previously remained elusive using other omics approaches and thus provide significant insight into the mechanisms of U resistance by C. crescentus . In particular, we show that outer membrane transporters RsaF a and RsaF b , previously known as part of the S-layer export machinery, may confer U resistance by U efflux and/or by maintaining membrane integrity during U stress.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2015
detail.hit.zdb_id:
1481988-0
SSG:
12
Permalink