Accumulation of polyphosphate granules in Helicobacter pylori cells under anaerobic conditions

Department of Microbiology, Yamaguchi University School of Medicine, Minami-Kogushi 1-1-1, Ube City, Yamaguchi 755-8505 and *Pharmaceutical Development Research Laboratory, Tanabe Seiyaku, 2-2-50 Kawagishi, Toda, Saitama 335-0015, Japan Corresponding author: Dr T. Nakazawa (e-mail: nakazawa@ po.cc.yamaguchi-u.ac.jp). Received 25 May 1999; revised version accepted 6 Oct. 1999. Abstract Helicobacter pylori is known to transform to coccoid forms which might be involved in faecal–oral transmission. When the bacteria enter the intestine, they encounter anaerobiosis that is unfavourable for growth. The effect of anaerobiosis was investigated to determine whether H. pylori is viable under such conditions. H. pylori in the late logarithmic growth phase transformed from spiral to coccoid forms when transferred to and incubated anaerobically in fresh medium. Acridine orange staining indicated that the viability of coccoid forms was significantly reduced, but still measurable even at day 5 or 7 of anaerobic culture. The cells retained low but significant levels of the major sigma factor RpoD at day 5 or 7 of anaerobic culture. The cellular structures of coccoid forms contained polyphosphate granules at day 1 and even at day 7 when incubated anaerobically, whereas only a few granules were observed under micro-aerobic conditions. Poor formation of polyphosphate granules in micro-aerobic cultures correlated particularly well with lower levels of acridine orange staining. These results suggest that acridine orange-positive anaerobic coccoid forms are viable to a certain extent and that polyphosphate may support this viability.