Effect of carbon-starvation on the survival of and PNP degradation by a Moraxella strain

Abstract

The effect of carbon-starvation on the stress resistance responses of a p-nitrophenol degrading Moraxella strain was examined in both, buffer and river water samples. The Moraxella strain showed optimal stress resistance responses in a minimal salt buffer when carbon-starved for 1-2 days. In the buffer system, the 1- and 2-day carbon-starved Moraxella cultures survived about 150-, 200- and 100-foid better than the non-starved cultures when exposed to 43.5°C, 2.7M NaCI and 500 " H2O2 for 4 hours, respectively. A green fluorescent protein gene- labelled derivative of the Moraxella strain was used to examine the stress resistance responses of the bacterium in natural river water microcosms. The carbon-starved gfp-labelled Moraxella strain also showed stress resistant responses against heat, osmotic and oxidative stresses in the river water samples. Despite the stress tolerant capability of the carbon-starved gfp-labelled Moraxella cells, they did not exhibit any survival advantage over their non-starved counterparts when inoculated into river water microcosms and incubated at 10° or 22°C for fourteen days.