AUTHOR=Lara Paloma , Vega-Alvarado Leticia , Sahonero-Canavesi Diana X. , Koenen Michel , Villanueva Laura , Riveros-Mckay Fernando , Morett Enrique , Juárez Katy 

TITLE=Transcriptome Analysis Reveals Cr(VI) Adaptation Mechanisms in Klebsiella sp. Strain AqSCr

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.656589

DOI=10.3389/fmicb.2021.656589

ISSN=1664-302X

ABSTRACT=Klebsiella sp. strain AqSCr, isolated from Cr(VI)-polluted groundwater, reduces Cr(VI) both aerobically and anaerobically, and resists up 34 mM Cr(VI); this resistance is independent of the ChrA efflux transporter. In this study, we report the whole genome sequence and the transcriptional profile of the strain AqSCr in the Cr(VI)-adapted stage obtained by RNA-Seq, finding 255 upregulated and 240 downregulated genes with respect to controls without Cr(VI) supplementation. Genes differentially transcribed were mostly associated with oxidative stress response, DNA repair and replication, sulfur starvation response, envelope-osmotic stress response, fatty acid metabolism, ribosomal subunits, and energy metabolism. Among them, genes not previously associated with chromium resistance, for example, cybB, encoding a putative superoxide oxidase (SOO), gltA2, encoding an alternative citrate synthase, and des, encoding a fatty acid desaturase, were upregulated. The sodA gene encoding a manganese superoxide dismutase was upregulated in the presence of Cr(VI), while sodB encoding an iron superoxide dismutase was downregulated. Cr(VI) resistance mechanisms in the strain AqSCr seem to be orchestrated by the alternative sigma factors fecl, rpoE and rpoS (all of them upregulated). Membrane lipid analysis of the Cr(IV)-adapted strain showed a lower proportion of unsaturated lipids with respect to the control, which we hypothesized it could result from unsaturated lipid peroxidation followed by degradation together with de novo synthesis mediated by the upregulated des fatty acid desaturase coding gene. This report helps to elucidate both Cr(VI) toxicity targets and global bacterial response to Cr(VI).