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Abstract Microbial cells must continually adapt their physiology in the face of changing environmental conditions. Archaea living in extreme conditions, such as saturated salinity, represent important examples of such resilience. The model salt‐loving organismHaloferax volcaniiexhibits remarkable plasticity in its morphology, biofilm formation, and motility in response to variations in nutrients and cell density. However, the mechanisms regulating these lifestyle transitions remain unclear. In prior research, we showed that the transcriptional regulator, TrmB, maintains the rod shape in the related speciesHalobacterium salinarumby activating the expression of enzyme‐coding genes in the gluconeogenesis metabolic pathway. InHbt. salinarum, TrmB‐dependent production of glucose moieties is required for cell surface glycoprotein biogenesis. Here, we use a combination of genetics and quantitative phenotyping assays to demonstrate that TrmB is essential for growth under gluconeogenic conditions inHfx. volcanii. The ∆trmBstrain rapidly accumulated suppressor mutations in a gene encoding a novel transcriptional regulator, which we nametrmBsuppressor, or TbsP (a.k.a. “tablespoon”). TbsP is required for adhesion to abiotic surfaces (i.e., biofilm formation) and maintains wild‐type cell morphology and motility. We use functional genomics and promoter fusion assays to characterize the regulons controlled by each of TrmB and TbsP, including joint regulation of the glucose‐dependent transcription ofgapII, which encodes an important gluconeogenic enzyme. We conclude that TrmB and TbsP coregulate gluconeogenesis, with downstream impacts on lifestyle transitions in response to nutrients inHfx. volcanii.
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GlpR Is a Direct Transcriptional Repressor of Fructose Metabolic Genes in Haloferax volcanii
ABSTRACT DeoR-type helix-turn-helix (HTH) domain proteins are transcriptional regulators of sugar and nucleoside metabolism in diverse bacteria and also occur in select archaea. In the model archaeon Haloferax volcanii , previous work implicated GlpR, a DeoR-type transcriptional regulator, in the transcriptional repression of glpR and the gene encoding the fructose-specific phosphofructokinase ( pfkB ) during growth on glycerol. However, the global regulon governed by GlpR remained unclear. Here, we compared transcriptomes of wild-type and Δ glpR mutant strains grown on glycerol and glucose to detect significant transcript level differences for nearly 50 new genes regulated by GlpR. By coupling computational prediction of GlpR binding sequences with in vivo and in vitro DNA binding experiments, we determined that GlpR directly controls genes encoding enzymes involved in fructose degradation, including fructose bisphosphate aldolase, a central control point in glycolysis. GlpR also directly controls other transcription factors. In contrast, other metabolic pathways appear to be under the indirect influence of GlpR. In vitro experiments demonstrated that GlpR purifies to function as a tetramer that binds the effector molecule fructose-1-phosphate (F1P). These results suggest that H. volcanii GlpR functions as a direct negative regulator of fructose degradation during growth on carbon sources other than fructose, such as glucose and glycerol, and that GlpR bears striking functional similarity to bacterial DeoR-type regulators. IMPORTANCE Many archaea are extremophiles, able to thrive in habitats of extreme salinity, pH and temperature. These biological properties are ideal for applications in biotechnology. However, limited knowledge of archaeal metabolism is a bottleneck that prevents the broad use of archaea as microbial factories for industrial products. Here, we characterize how sugar uptake and use are regulated in a species that lives in high salinity. We demonstrate that a key sugar regulatory protein in this archaeal species functions using molecular mechanisms conserved with distantly related bacterial species.
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- PAR ID:
- 10096679
- Date Published:
- Journal Name:
- Journal of Bacteriology
- Volume:
- 200
- Issue:
- 17
- ISSN:
- 0021-9193
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1128/JB.00244-18
