Improved growth and morphological plasticity of Haloferax volcanii

Abstract

Some microbes display pleomorphism, showing variable cell shapes in a single culture, whereas others differentiate to adapt to changed environmental conditions. The pleomorphic archaeon Haloferax volcanii commonly forms discoid-shaped (‘plate’) cells in culture, but may also be present as rods, and can develop into motile rods in soft agar, or longer filaments in certain biofilms. Here we report improvement of H. volcanii growth in both semi-defined and complex media by supplementing with eight trace element micronutrients. With these supplemented media, transient development of plate cells into uniformly shaped rods was clearly observed during the early log phase of growth; cells then reverted to plates for the late log and stationary phases. In media prepared with high-purity water and reagents, without supplemental trace elements, rods and other complex elongated morphologies (‘pleomorphic rods’) were observed at all growth stages of the culture; the highly elongated cells sometimes displayed a substantial tubule at one or less frequently both poles, as well as unusual tapered and highly curved forms. Polar tubules were observed forming by initial mid-cell narrowing or tubulation, causing a dumbbell-like shape, followed by cell division towards one end. Formation of the uniform early log-phase rods, as well as the pleomorphic rods and tubules were dependent on the function of the tubulin-like cytoskeletal protein, CetZ1. Our results reveal the remarkable morphological plasticity of H. volcanii cells in response to multiple culture conditions, and should facilitate the use of this species in further studies of archaeal biology.

Comprehensive glycoproteomics shines new light on the complexity and extent of glycosylation in archaea

“…Hfx . volcanii has been described to change from rod-shaped cells in early-logarithmic growth phase to disk-shaped cells in the late-logarithmic growth phase [ 31 – 33 ]. While we observed the same trend for all strains analyzed here, interestingly, the cell shape of both N -glycosylation pathway mutants differed from that of the WT strain at different stages of the growth curve ( Fig 2B ).…”

“…In addition to SLG, the AglB-dependent N -glycosylation of ABC transporters that we identified here could have an effect on (micro-)nutrient acquisition in Hfx . volcanii , which has been linked to cell shape as well [ 31 ]. This may also explain differing growth curves between the WT and especially the Δ aglB strain.…”

“…Hfx . volcanii H53, as well as the Δ aglB and Δ agl15 mutants, was grown at 45°C in liquid or on solid agar semi-defined casamino acid (Hv-Cab) medium [ 31 ]. H53 cultures were supplemented with tryptophan (+Trp) and uracil (+Ura) at a final concentration of 50 μg ml −1 .…”

Open Issues for Protein Function Assignment in Haloferax volcanii and Other Halophilic Archaea

“…Its genome has been sequenced and carefully annotated [ 1 , 10 , 11 ]. A plethora of biological aspects have been successfully tackled in this species, with examples including DNA replication [ 4 ]; cell division and cell shape [ 12 , 13 , 14 , 15 , 16 ]; metabolism [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]; protein secretion [ 26 , 27 , 28 , 29 ]; motility and biofilms [ 30 , 31 , 32 , 33 , 34 , 35 ]; mating [ 36 ]; signaling [ 37 ]; virus defense [ 38 ]; proteolysis [ 39 , 40 , 41 , 42 , 43 , 44 ]; posttranslational modification (N-glycosylation; SAMPylation) [ 45 , 46 , 47 , 48 , 49 , 50 ]; gene regulation [ 21 , 25 , 51 , 52 , 53 , 54 , 55 ]; microproteins [ 56 , 57 , 58 ] and small noncoding RNAs (sRNAs) […”

Microbial Musings – February 2021

“…This month our Editor’s choice has been chosen by senior editor Tracy Palmer FRS and is the second paper in this issue from authors at the iThree Institute ( @ithreeinst ), University of Technology, Sydney, Australia. This paper from Roshali De Silva ( @RoshaliDe ), Hannah Brown ( @hannjbrown ) and colleagues in the group of Iain Duggin ( @iduggin ), collaborating with Mecky Pohlschröder ( @pohlschr ) at the University of Pennsylvania, USA, provides an improved growth medium to study the weird and wonderful morphological plasticity of the archaeon Haloferax volcanii [ 22 ]. This microbe can change from a discoid-shaped cell to a classical rod-shaped cell, and populations grown in existing media would often have multiple types.…”