Nuclear Fusion in Spirillum spp

SUMMARY: Cellular fusion of entwined fresh-water spirilla, Spirillum sinuosum and S. anulus, is followed by nuclear fusion. Evidence of nuclear fusion was obtained from impression smears (fixed in acetic-alcohol, hydrolysed in n-HC1 and stained with Giemsa) made at regular time intervals during the growth of cultures of these organisms. Following cellular fusion and nuclear fusion of opposing granules into rings of six granules, with the coalescence of the rings into a single, elongate body, the fusion cells enlarge into ‘giant’ organisms. The chromatinic bodies of these giants divide or separate into numerous rod-like chromatin structures around the vacuoles found in the later stages. The giant organisms either give off or fragment into small rod-like bodies, containing, at first, a triangular-shaped chromatinic structure. This triangular chromatinic structure condenses into a single spherical body as the small rod-like organisms are more clearly formed. The fate of these small rod-like organisms is unknown, but similar rod-like bodies which develop into the normal spirillum have been observed in young cultures of both S. sinuosum and S. anulus. Nothing resembling classical mitosis or meiosis was observed in any of the stained preparations of either organism.