Haloferax volcanii immersed liquid biofilms develop independently of known biofilm machineries and exhibit rapid honeycomb pattern formation

Abstract

The ability to form biofilms is shared by many microorganisms, including archaea. Cells in a biofilm are encased in extracellular polymeric substances that typically include polysaccharides, proteins, and extracellular DNA, conferring protection while providing a structure that allows for optimal nutrient flow. In many bacteria, flagella and evolutionarily conserved type IV pili are required for the formation of biofilms on solid surfaces or floating at the air-liquid interface of liquid media. Similarly, in many archaea it has been demonstrated that type IV pili and, in a subset of these species, archaella are required for biofilm formation on solid surfaces. In the model archaeon Haloferax volcanii, chemotaxis and AglB-dependent glycosylation also play a role in this process. H. volcanii also forms immersed biofilms in liquid cultures poured into Petri dishes. This study reveals that mutants of this haloarchaeon that interfere with the biosynthesis of type IV pili or archaella, as well as chemotaxis transposon and aglB-deletion mutants, lack obvious defects in biofilms formed in liquid cultures. Strikingly, we have observed that these liquid-based biofilms are capable of rearrangement into honeycomb-like patterns that rapidly form upon removal of the Petri-dish lid and are not dependent on changes in light, oxygen, or humidity. Taken together, this study demonstrates that H. volcanii requires novel, as yet unidentified strategies for immersed liquid biofilm formation and also exhibits rapid structural rearrangements, providing the first evidence for a potential role for volatile signaling in H. volcanii.

Advanced understanding of prokaryotic biofilm formation using a cost-effective and versatile multi-panel adhesion (mPAD) mount

“…While the haloarchaeon H. volcanii has been used as a model organism to study biofilm formation in archaea (15, 16, 23), to our knowledge, biofilm assays have not been performed under shaking conditions for any archaeon so far. Using the mPAD assay under shaking conditions, we could show that, similar to P. aeruginosa, H. volcanii can form biofilms under shaking conditions but exhibits distinct biofilm architectures depending on the exposure to shear forces (Fig.…”

Open issues for protein function assignment inHaloferax volcaniiand other halophilic archaea

“…Its genome has been sequenced and carefully annotated (Hartman et al, 2010, Pfeiffer et al, 2008a, Pfeiffer and Oesterhelt, 2015. A plethora of biological aspects have been successfully tackled in this species, with examples including DNA replication (Perez-Arnaiz et al, 2020); cell division and cell shape (Turkowyd et al, 2020, Walsh et al, 2019, de Silva et al, 2021, Duggin et al, 2015, Liao et al, 2021; metabolism (Brasen and Schonheit, 2001, Johnsen et al, 2009, Pickl et al, 2012, Sutter et al, 2016, Reinhardt et al, 2019, Kuprat et al, 2021, Kuprat et al, 2020, Sutter et al, 2020, Tästensen et al, 2020; protein secretion (Abdul-Halim et al, 2020, Abdul Halim et al, 2018, Abdul Halim et al, 2013, Storf et al, 2010; motility and biofilms (Schiller et al, 2020, Pohlschroder and Esquivel, 2015, Li et al, 2020, Collins et al, 2020, Quax et al, 2018, Nussbaum et al, 2020; mating (Shalev et al, 2017); signalling (Braun et al, 2019); virus defence (Maier et al, 2019); proteolysis (Reuter and Maupin-Furlow, 2004, Reuter et al, 2010, Prunetti et al, 2014, Cerletti et al, 2014, Costa et al, 2018; posttranslati...…”