Effect of changes in mineral composition and growth temperature on filament length and flagellation in the Archaeon Methanospirillum hungatei

Abstract

Methanospirillum hungatei strains GP1 and JF1 when cultivated at 37°C in JMA medium grew as motile single cells or short chains of cells (typically 10–30 μm long). When M. hungatei was grown in low Ca²⁺ concentrations or with the divalent cation chelator EDTA, the organism grew as long non-flagellated filaments (up to 900 μm long). The two strains had different thresholds of calcium concentrations for long filament formation (<0.25 mM for GP1 and <0.15 mM for JF1) as well as different minimal Ca²⁺ requirements for growth. Both strains produced long, almost straight, filaments at Ca²⁺ concentrations near the minimum required for growth. At suboptimal growth temperatures the organisms still grew as short filaments but no longer possessed flagella. Western blot analysis indicated that flagellin monomer was present in cultures of long non-flagellated filaments and short non-flagellated cultures grown at suboptimal temperatures. The amount of flagellin present appeared to be equal in both non-flagellated and flagellated cultures. When cells were grown as long non-flagellated filaments and switched to growth conditions inducing short, flagellated forms, flagella were first observed at 2.5 h after this switch.