title: Characterization of zinc stress response in Cyanobacterium Synechococcus sp. IU 625.
abstract: The ability of cyanobacteria to survive many environmental stress factors is a testament to their resilience in nature. Of these environmental stress factors, overexposure to zinc is important to study since excessive zinc intake can be a severe hazard. Zinc toxicity in freshwater has been demonstrated to affects organisms such as invertebrates, algae and cyanobacteria. Cyanobacteria which possess increased resistance to zinc have been isolated. It is therefore important to elucidate the mechanism of survival and response to determine what factors allow their survival; as well as any remediation implications they may have. To characterize the effects of zinc in freshwater cyanobacteria, we investigated the response of Synechococcus sp. IU 625 (S. IU 625) over 29days to various concentrations (10, 25, and 50mg/L) of ZnCl2. S. IU 625 was shown to be tolerant up to 25mg/L ZnCl2exposure, with 10mg/L ZnCl2having no outward physiological change and 50mg/L ZnCl2proving lethal to the cells. To determine a potential mechanism Inductive Coupled Plasma-Mass Spectrometry (ICP-MS) and RNA-seq analysis were performed on zinc exposed cells. Analysis performed on days 4 and 7 indicated that response is dose-dependent, with 10mg/L ZnCl2exhibiting nearly all zinc extracellular, corresponding with upregulation of cation transport response. Whereas the 25mg/L ZnCl2exhibited half of total zinc sequestered by the cells, which corresponds with the upregulation of sequestering proteins such as metallothionein and the downregulation of genes involved with ATP synthesis and phycobilisome assembly. These analyses were combined with growth monitoring, microscopy, quantitative polymerase chain reaction (qPCR) and flow cytometry to present a full spectrum of mechanisms behind zinc response in S. IU 625.
authors.affiliation: Department of Biological Sciences, Seton Hall University, South Orange, NJ, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Newby
authors.affiliation: Department of Biology, Montclair State University, Montclair, NJ, USA.
authors.forename: Lee H
authors.initials: LH
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, Seton Hall University, South Orange, NJ, USA.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Perez
authors.affiliation: Department of Biological Sciences, Seton Hall University, South Orange, NJ, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Tao
authors.affiliation: Department of Biological Sciences, Seton Hall University, South Orange, NJ, USA. Electronic address: Tin-Chun.Chu@shu.edu.
authors.forename: Tinchun
authors.initials: T
authors.lastname: Chu
mesh_terms: D002712:Chlorides / Q000633:toxicity*; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects; D016133:Polymerase Chain Reaction; D013054:Spectrophotometry, Atomic; D013312:Stress, Physiological / Q000187:drug effects*; D046940:Synechococcus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D059467:Transcriptome / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000633:toxicity; D015032:Zinc / Q000378:metabolism; D017967:Zinc Compounds / Q000633:toxicity*
chemical_list: D002712:Chlorides; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds; C016837:zinc chloride; D015032:Zinc
keywords: Adaptation; Cyanobacteria; Gene expression; Metal; Stress response