A complex aggregation of microorganisms growing on a solid substrate is termed a biofilm and is considered to be an etiological agents.
Pseudomonas aeruginosa and
Streptococcus mutans are representative bacteria in such biofilms. It is well known that deuterium oxide (D
2O) causes toxic effects on a number of biological systems. We investigated the effects of D
2O on growth and biofilm formation of
P. aeruginosa and
S. mutans. These bacteria were incubated in medium containing D
2O (100%, 75% or 0%) at 37°C for 24hr, 48hr or 72hr. Growth of
P. aeruginosa was inhibited by D
2O within the first 48hr. However, after 72hr, growth rate was seen to increase in the D
2O-containing medium compared with in medium without D
2O. In contrast, the growth of
S. mutans in the D
2O medium was inhibited within 72hr. The biofilm formation of
P. aeruginosa was increased in the D
2O medium. Biofilm formation of S. mutans in the D
2O medium increased compared with in the medium without D
2O, but this increase was only temporary in the case of
P. aeruginosa. Compared to biofilm formation in 0% D
2O medium marked as 100%, the biofilm formation rate of
S. mutans in 75% D
2O medium was 143% at 24hr, 146% at 48hr and 130% at 72hr. In other D
2O concentration media biofilm formation was lower. In 100% D
2O medium, biofilm formation rate decreased from 114% at 24hr to 56% at 72hr. The biofilm formation rate of
P. aeruginosa in 100% D
2O medium was 172% at 24hr, but decreased to 88% at 72hr. Biofilm formation of
P. aeruginosa in 75% and 0% D
2O media showed no significant difference. We consider that these results were due to stress or alteration in bacterial metabolisms.
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