Diatom cell culture and image acquisition
The Navicula arenaria var. rostellata strain 0488 (size
ranges from 30~50 \(\mu\)m in length and
5~15 \(\mu\)m in width) is maintained in the BCCM/DCG
diatom culture collection at Ghent University,
http://bccm.belspo.be/about-us/bccm-dcg. It was isolated in
January 2013 from high-nitrate intertidal flats of Paulina Schor, The
Netherlands (51°21’N, 3°43’E). The isolate has since been maintained in
unialgal culture in artificial seawater medium Aquil (f/2+Si). Like
other naviculoid diatoms, N. arenaria is boat-shaped with on each
valve a raphe, a specialized slit in their silica cell wall, running
along its longitudinal axis. Although the precise mechanism remains
unknown, diatom gliding involves an actin/myosin motility system and the
secretion of adhesive EPS strands through the raphe (46).
Diatom culture were maintained using a standard protocol. One months
before the experiment, cells were acclimated to 2000 Lux light intensity
with a light dark cycle of 12:12 hours (INFORS HT Multitron pro,
Switzerland). A 100 ml flask suspension was grown on a shaker at 20°C
rotating with 100 rpm. For motility experiments, diatom cells at period
of exponential phase were diluted with filtered autoclaved seawater and
introduced into the test chamber for observations. The densities of
individuals (about 15 cells/mm2) were used in order to
minimize effects of cell-cell interference.