Table 2. Natural transformation is dependent on cAMP, which is produced by adenylate cyclase (CyaA) and degraded by cAMP-degrading phosphodiesterase (CpdA).

V. cholerae strain	Competence induced#	Transformation frequency (±SD)
A1552-TntfoX	No	<d.l.
A1552-TntfoX	Yes	2.1×10−4 (±1.9×10−4)
ΔcyaA-TntfoX	No	<d.l.
ΔcyaA-TntfoX	Yes	<d.l.
ΔcpdA-TntfoX	No	<d.l.
ΔcpdA-TntfoX	Yes	7.1×10−4 (±4.7×10−4)*

^#Competence was induced by the addition of 0.02% arabinose wherever indicated.

<d.l.: below detection limit;

*: Statistically significant difference in comparison to the wild type strain A1552-TntfoX; P<0.05; Average of at least three independent experiments.