This study examines the effect of
carbon starvation on the ability of a Moraxella sp. strain to degrade
p-nitrophenol (PNP).
Carbon starvation for 24 h decreased the induction time for
p-nitrophenol degradation by the bacterium in a minimal
salt medium from 6 to 1 h but it did not completely eliminate the induction time. Moraxella cells with 2-day
carbon starvation had an induction time of 3 h and the induction time of the 3-day starved cells was 6 h. A 100% increase in density of the non-starved cells did not affect the induction time for
p-nitrophenol degradation by the bacterium, indicating that the initial increase in cell density of the
carbon-starved culture did not cause the faster onset of
p-nitrophenol degradation. However, the initial uptake of
p-nitrophenol of the 1-day
carbon-starved Moraxella cells was 3-fold higher than the non-starved cells. A
green fluorescent protein gene (gfp)-labelled Moraxella (M6 strain) was constructed to examine the survival of and
p-nitrophenol degradation by the bacterium in non-sterile river water samples. Similar
p-nitrophenol degradation behaviour was observed in the river water samples inoculated with the M6 cells. The time needed for complete degradation of
p-nitrophenol by the non-starved M6 was 19-27 and 33 h in samples spiked with 80, 200 and 360 microM
p-nitrophenol, respectively. However, the 1-day
carbon-starved inocula required about 16 h to degrade the
p-nitrophenol completely regardless of its concentration in the water samples. Survival of the
carbon-starved and non-starved M6 was not significantly different from each other in the river water regardless of the
p-nitrophenol concentration. In the absence of
p-nitrophenol, the inoculum density decreased continuously. At 200 and 360 microM
p-nitrophenol, the cell densities of M6 increased in the first two days of incubation and declined steadily afterward.