title: Transcriptomic analysis reveals how a lack of potassium ions increases Sulfolobus acidocaldarius sensitivity to pH changes.
abstract: Extremely acidophilic microorganisms (optimum growth pH of ≤3) maintain a near neutral cytoplasmic pH via several homeostatic mechanisms, including an inside positive membrane potential created by potassium ions. Transcriptomic responses to pH stress in the thermoacidophilic archaeon, Sulfolobus acidocaldarius were investigated by growing cells without added sodium and/or potassium ions at both optimal and sub-optimal pH. Culturing the cells in the absence of added sodium or potassium ions resulted in a reduced growth rate compared to full-salt conditions as well as 43 and 75 significantly different RNA transcript ratios, respectively. Differentially expressed RNA transcripts during growth in the absence of added sodium ions included genes coding for permeases, a sodium/proline transporter and electron transport proteins. In contrast, culturing without added potassium ions resulted in higher RNA transcripts for similar genes as a lack of sodium ions plus genes related to spermidine that has a general role in response to stress and a decarboxylase that potentially consumes protons. The greatest RNA transcript response occurred when S. acidocaldarius cells were grown in the absence of potassium and/or sodium at a sub-optimal pH. These adaptations included those listed above plus osmoregulated glucans and mechanosensitive channels that have previously been shown to respond to osmotic stress. In addition, data analyses revealed two co-expressed IclR family transcriptional regulator genes with a previously unknown role in the S. acidocaldarius pH stress response. Our study provides additional evidence towards the importance of potassium in acidophile growth at acidic pH.
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.|Centre for Biomaterials Chemistry, Linnaeus University, Kalmar, Sweden.
authors.forename: Antoine
authors.initials: A
authors.lastname: Buetti-Dinh
authors.affiliation: National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Stockholm University, Stockholm, Sweden.
authors.forename: Olga
authors.initials: O
authors.lastname: Dethlefsen
authors.affiliation: Centre for Biomaterials Chemistry, Linnaeus University, Kalmar, Sweden.
authors.forename: Ran
authors.initials: R
authors.lastname: Friedman
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
authors.forename: Mark
authors.initials: M
authors.lastname: Dopson
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D020869:Gene Expression Profiling; D006863:Hydrogen-Ion Concentration; D008465:Mechanoreceptors / Q000502:physiology; D009997:Osmotic Pressure / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013095:Spermidine / Q000378:metabolism; D016945:Sulfolobus acidocaldarius / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D015534:Trans-Activators; D012964:Sodium; D011188:Potassium; D013095:Spermidine