RESULTS AND DISCUSSION
It was found that carnation soil and roots samples contained
several groups of bacteria when they were cultured
on DF media. In order to search for some bacteria
with ACC-degrading ability, carnation soil and roots were
plated in DF medium without (NH4)2SO4 supplemented
with ACC as the sole nitrogen source for the isolation of
ACC-degrading bacteria, meanwhile, Bacillus subtilis
without ACC deaminase-containing activity was used as
the control during all the screening procedures (Figure 1).
The five colonies of ACC deaminase-containing bacteria,
including four from soil (designated CS1, CS2, CS3 and
CS4) and one from roots (designated CR1), were successfully
screened by ADF media, respectively.
All the isolated bacteria had a marked ACC deaminase
activity after incubation at 28°C, which could use ACC as
a sole nitrogen substrate and catalyse it into ammonia
and α-ketobutyrate. ACC deaminase activities of five different
strains isolated in this study were measured and
shown (Figure 2). We found that there existed much
difference among the strains in the activities of ACC
degradation, especially CS2 strain which had the highest
level of ACC deaminase activity among the five isolated
strains (Figure 2). Microscopic examination revealed that
all the strains isolated in this study were Gram-negative,
the cells appeared rods, and different strains had their
own growth morphological characters (data not shown).