TbsP and TrmB jointly regulate gapII to influence cell development phenotypes in the archaeon Haloferax volcanii

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 organism Haloferax volcanii exhibits 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 species Halobacterium salinarum by activating the expression of enzyme‐coding genes in the gluconeogenesis metabolic pathway. In Hbt. 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 in Hfx. volcanii. The ∆trmB strain rapidly accumulated suppressor mutations in a gene encoding a novel transcriptional regulator, which we name trmB suppressor, 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 of gapII, which encodes an important gluconeogenic enzyme. We conclude that TrmB and TbsP coregulate gluconeogenesis, with downstream impacts on lifestyle transitions in response to nutrients in Hfx. volcanii.

Dynamic self-association of archaeal tubulin-like protein CetZ1 drivesHaloferax volcaniimorphogenesis

“…This type of morphogenic transformation occurs in a variety of conditions, including for motility, early-log phase growth, and in response to micronutrient depletion 18,22 . CetZ1 is also expected to be essential in other conditions that promote rod development or cell elongation 23,24 . Based on monomer and protofilament crystal structures 18 , and the common properties of TSF proteins 25 , CetZs are predicted to polymerize through binding GTP, forming protofilaments and potentially higher-order assemblies like those of tubulin and FtsZ.…”