Molecular Factors of Hypochlorite Tolerance in the Hypersaline Archaeon Haloferax volcanii

Abstract

Halophilic archaea thrive in hypersaline conditions associated with desiccation, ultraviolet (UV) irradiation and redox active compounds, and thus are naturally tolerant to a variety of stresses. Here, we identified mutations that promote enhanced tolerance of halophilic archaea to redox-active compounds using Haloferax volcanii as a model organism. The strains were isolated from a library of random transposon mutants for growth on high doses of sodium hypochlorite (NaOCl), an agent that forms hypochlorous acid (HOCl) and other redox acid compounds common to aqueous environments of high concentrations of chloride. The transposon insertion site in each of twenty isolated clones was mapped using the following: (i) inverse nested two-step PCR (INT-PCR) and (ii) semi-random two-step PCR (ST-PCR). Genes that were found to be disrupted in hypertolerant strains were associated with lysine deacetylation, proteasomes, transporters, polyamine biosynthesis, electron transfer, and other cellular processes. Further analysis revealed a ΔpsmA1 (α1) markerless deletion strain that produces only the α2 and β proteins of 20S proteasomes was hypertolerant to hypochlorite stress compared with wild type, which produces α1, α2, and β proteins. The results of this study provide new insights into archaeal tolerance of redox active compounds such as hypochlorite.

Insights into the Lysine Acetylome of the Haloarchaeon Haloferax volcanii during Oxidative Stress by Quantitative SILAC-Based Proteomics

“…Overall, these impacts in the proteome of a ∆sir2 mutant can imply a potential challenge during hypochlorite stress in the strain, suggesting an important function of Sir2 for this response. While a transposon mutant of sir2 was shown to be hyper tolerant [ 19 ], transposon insertions can influence the expression of adjacent genes and/or other mutations may have occurred on the genome.…”

“…In this present study, we aim to define the role of lysine acetylation during oxidative stress response in H. volcanii . The rationale for this focus is based on our previous finding that oxidative stress: (i) stimulates an increase in the abundance ratios of the lysine acetyltransferase homologs Hv Pat2 to Hv Pat1 and (ii) selects for the survival of a sir2 transposon mutant [ 12 , 19 ]. Here a quantitative comparison of the lysine acetylome is presented during the presence vs. absence of hypochlorite stress.…”

Rat Glioma Cell-Based Functional Characterization of Anti-Stress and Protein Deaggregation Activities in the Marine Carotenoids, Astaxanthin and Fucoxanthin

“…Anomalies in DNA damage repair mechanisms often cause mutations and lead to the development of cancer, early aging, and several degenerative diseases. Chronic exposure to these stresses leads to continual protein misfolding and aggregation [42,43]. These aggregates contribute to age-related degenerative pathologies to a large extent [1,44,45,46].…”

Insights through Genetics of Halophilic Microorganisms and Their Viruses

“…Halophilic archaea are masters at handling stress as these microbes thrive in hypersaline environments that promote hyperosmotic shock, desiccation, high UV exposure and other extreme factors. By screening a transposon mutant library of Haloferax volcanii, Gomez et al [10] probed the molecular factors responsible for oxidative stress response. Transposon mutants hypertolerant of oxidant were isolated and found to have insertions at loci associated with post-translational modification, transport, polyamine biosynthesis, electron transfer and other cellular processes.…”