Living with two extremes: Conclusions from the genome sequence of Natronomonas pharaonis

Abstract

Natronomonas pharaonis is an extremely haloalkaliphilic archaeon that was isolated from salt-saturated lakes of pH 11. We sequenced its 2.6-Mb GC-rich chromosome and two plasmids (131 and 23 kb). Genome analysis suggests that it is adapted to cope with severe ammonia and heavy metal deficiencies that arise at high pH values. A high degree of nutritional self-sufficiency was predicted and confirmed by growth in a minimal medium containing leucine but no other amino acids or vitamins. Genes for a complex III analog of the respiratory chain could not be identified in the N. pharaonis genome, but respiration and oxidative phosphorylation were experimentally proven. These studies identified protons as coupling ion between respiratory chain and ATP synthase, in contrast to other alkaliphiles using sodium instead. Secretome analysis predicts many extracellular proteins with alkaline-resistant lipid anchors, which are predominantly exported through the twin-arginine pathway. In addition, a variety of glycosylated cell surface proteins probably form a protective complex cell envelope. N. pharaonis is fully equipped with archaeal signal transduction and motility genes. Several receptors/transducers signaling to the flagellar motor display novel domain architectures. Clusters of signal transduction genes are rearranged in haloarchaeal genomes, whereas those involved in information processing or energy metabolism show a highly conserved gene order.

Optogenetic control of epileptiform activity

“…This article is a PNAS Direct Submission. 1 To whom correspondence should be addressed. E-mail: merab.kokaia@med.lu.se.…”

“…epilepsy ͉ hippocampus ͉ NpHR ͉ paroxysmal depolarizing shift (PDS) ͉ stimulation train-induced bursting (STIB) W hen archaebacterium Natronomonas pharaonis, living in hyperosmotic conditions of lake Zug in the Sahara desert, is exposed to light, its inward-directed halorhodopsin chloride pump (NpHR) is ativated to create a life-saving membrane potential, which drives across the membrane protons (and other cations) used for ATP synthesis (1,2). Genetically adapted to be expressed in mammalian brain by viral vectors and optically activated with millisecond precision, the transgene NpHR pumps chloride ions into transduced neurons, hyperpolarizing and preventing them from firing action potentials (3,4).…”

A re-evaluation of the archaeal membrane lipid biosynthetic pathway

“…It has been previously suggested that this FGPP synthase has evolved from an ancestral IPP synthase of Desulfurococcales (Tabichana et al, 2000). **bifunctional geranyl/farnesylgeranyl diphosphate synthase (C 20 and C 25 , respectively) described in the Halobacteriales Natronomonas pharaonis (Falb et al, 2005). Table S2.…”

Salt-driven Equilibrium between Two Conformations in the HAMP Domain from Natronomonas pharaonis

“…N. pharaonis is an extremely haloalkaliphilic archaeon, living in salt-saturated lakes (15) at pH values around 11 (16) and temperatures of optimal growth in the 318 -323 K range (17,18). Cytoplasmic and external salt concentrations can be assumed to be similar, however, with reversed sodium to potassium ratio (19).…”