The bacterial cells were grown in MRS broth for 2 days at 30 C
for morphology observation with scanning electron microscopy
(SEM). Cells were collected by centrifugation at 5000 rpm for
10 min and washed with 0.1 mol l1 phosphate buffered saline
(PBS, pH 7.0) for two times. The pellets were suspended in 2.5%
glutaraldehyde solution (2.5% glutaraldehyde dissolved in
0.1 mol l1 phosphate buffered saline, pH 7.2) and kept at 4 C for
5 h. After that, the cells were wash with 30%, 50%, 70% ethanol in
turn and vacuum freeze dried for 24 h before the observation. The
cells were coated with gold and observed with a JSM-6390LV SEM.