Physiological regulation of competence induction for natural transformation in Acinetobacter calcoaceticus

Abstract

Acinetobacter calcoaceticus induced competence for natural transformation maximally after dilution of a stationary culture into fresh medium. Competence was gradually lost during prolonged exponential growth and after entrance into the stationary state. Growth cessation and nutrient upshift were involved in the induction of competence. The level of competence of a chemostat culture of A. calcoaceticus was dependent on the nature of the growth limitation. Under potassium limitation a transformation frequency of + 1 x 10 .4 was obtained. This frequency was independent of the specific growth rate. In phosphate-, nitrogen-, and carbon-limited chemostat cultures, in contrast, the transformation frequency depended on the specific growth rate; the transformation frequency equalled _+ 10.4 at dilution rates close to g,~a• of 0.6h -1 and decreased to _+ 10 -7 at a dilution rate of 0.1 h-L We conclude that (1) DNA uptake for natural transformation in A.calcoaceticus does not serve a nutrient function and (2) competence induction is regulated via a promoter(s) that resembles the fis promoter from Escherichia coli.

Cues and regulatory pathways involved in natural competence and transformation in pathogenic and environmental Gram-negative bacteria

“…Other groups provided evidence that the highest transformation frequencies occurred early in the exponential phase, which was consistent with rapid growth (Cruze et al ., ). The latter finding was also confirmed by several groups (Palmen et al ., , ; Porstendörfer et al ., ), who showed that natural transformation was maximally induced after the dilution of an overnight culture into fresh medium or ‘after an increase in nutrient availability, preceded by cessation of growth’ (Palmen et al ., ). In an earlier review, these contradictory findings were resolved with the conclusion that competence ‘reaches its maximum during early to late log phase in A. calcoaceticus ’ (Lorenz & Wackernagel, ).…”

“…Based on the results of a study on early competence induction, Palmen et al . () concluded that ‘the biological function of natural transformation in A. calcoaceticus is not to provide the cell with nutrients’ and that ‘the regulation of competence development as a function of the stringency of carbon, nitrogen, and phosphate limitation was just opposite to what one would expect if the ‘nutrient supply hypothesis’ would apply’.…”

The use of chemical profiling for monitoring metabolic changes in artificial soil slurries caused by horizontal gene transfer

“…Competent cells were prepared as before (Palmen et al, 1993(Palmen et al, , 1994 with slight modifications. Briefly, Acinetobacter sp.…”

comB , a novel competence gene required for natural transformation of Acinetobacter sp. BD413: identification, characterization, and analysis of growth-phase-dependent regulation

“…It is reasonable to suggest that different structural elements associated with transformation are expressed coordinately and function in an orchestrated manner. Interestingly, transcriptional activation of comB during the prolonged exponential growth phase does not correlate with competence development, as maximal competence is induced immediately after inoculation into fresh medium but is gradually lost during prolonged exponential growth (Palmen et al 1994;D. Porstendörfer, unpublished results).…”

“…BD413 stationary culture into fresh medium. During prolonged exponential growth competence is gradually lost until minimal transformation frequencies are reached in stationary phase (Palmen et al 1994;D. Porstendörfer, unpublished results).…”