Arsenate-dependent growth is independent of an ArrA mechanism of arsenate respiration in the termite hindgut isolate Citrobacter sp. strain TSA-1.

Author(s) Blum, J.Switzer; Hernandez-Maldonado, J.; Redford, K.; Sing, C.; Bennett, S.C.; Saltikov, C.W.; Oremland, R.S.
Journal Can J Microbiol
Date Published 2018 Sep
Abstract

Citrobacter sp. strain TSA-1 is an enteric bacterium isolated from the hindgut of the termite. Strain TSA-1 displays anaerobic growth with selenite, fumarate, tetrathionate, nitrate, or arsenate serving as electron acceptors, and it also grows aerobically. In regards to arsenate, genome sequencing revealed that strain TSA-1 lacks a homolog for respiratory arsenate reductase, arrAB, and we were unable to obtain amplicons of arrA. This raises the question as to how strain TSA-1 achieves As(V)-dependent growth. We show that growth of strain TSA-1 on glycerol, which it cannot ferment, is linked to the electron acceptor arsenate. A series of transcriptomic experiments were conducted to discern which genes were upregulated during growth on arsenate, as opposed to those on fumarate or oxygen. For As(V), upregulation was noted for 1 of the 2 annotated arsC genes, while there was no clear upregulation for tetrathionate reductase (ttr), suggesting that this enzyme is not an alternative to arrAB as occurs in certain hyperthermophilic archaea. A gene-deletion mutant strain of TSA-1 deficient in arsC could not achieve anaerobic respiratory growth on As(V). Our results suggest that Citrobacter sp. strain TSA-1 has an unusual and as yet undefined means of achieving arsenate respiration, perhaps involving its ArsC as a respiratory reductase as well as a detoxifying agent.

DOI 10.1139/cjm-2017-0523
Keywords Anaerobiosis; Animals; Arsenate Reductases; Arsenates; Bacterial Proteins; Citrobacter; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Bacterial; Genome, Bacterial; Isoptera; Mutation
ISSN 1480-3275
Citation Blum JS, Hernandez-Maldonado J, Redford K, Sing C, Bennett SC, Saltikov CW, et al. Arsenate-dependent growth is independent of an ArrA mechanism of arsenate respiration in the termite hindgut isolate Citrobacter sp. strain TSA-1. Can J Microbiol. 2018;64(9):619-627.

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