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    STUDIA BIOLOGIA - Issue no. 1 / 2019  
         
  Article:   COMPARATIVE STUDIES OF HALORUBRUM LACUSPROFUNDI ARCHAELLA SYNTHESIZED IN DIFFERENT WAYS.

Authors:  ANNA GALEVA, MIKHAIL PYATIBRATOV, ALEXEY SYUTKIN, TESSA E.F. QUAX, TATJANA MELNIK, ALEXEY SURIN, SERGEI BEZNOSOV, OLEG FEDOROV. 		 
       
         
  Abstract:   The role of multiplicity of archaellin genes in Euryarchaea remains mysterious. The haloarchaeon Halorubrum lacusprofundiDL18 possesses an operon with two archaellin genes encoding the extraordinarily diverged paralogs FlaB1 and FlaB2. In the archaellar filaments both proteins are represented in approximately equimolar amounts. We compared DL18 with another strain ACAM34 with only one flaB2 gene. Both strains synthesize functional archaella, but motility is better in DL18. Using heterologous expression in a Haloferax volcanii strain lacking its own archaellin genes, we obtained three recombinant filament types: B1, B2 and B1B2. All archaellin-expressing Hfx. volcanii strains were motile, indicating the recombinant archaella functionality. Like the natural Hrr. Lacusprofundi strains, the motility of cells with B2-filaments was significantly lower than for cells synthesizing B1B2- and B1-archaella. Electron microscopy of native and recombinant filaments showed that the B2-archaella are quite flexible and often twisted in loops and tangles, while the B1B2- and B1-archaella look like more typical. Both native and recombinant B1B2-filaments have greater thermal stability and resistance to low salinity stress than single-component filaments. The data obtained indicate a close interaction between the FlaB1 and FlaB2 in the filament structure. Thus, the two-component composition is needed for additional stabilization of the archaellum structure and adaptation to a wider range of external conditions and is not necessary for archaella supercoiling.

Keywords: archaella, archaellins, Halorubrum lacusprofundi, motility. 		 
         
     
         
         
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