Physiologischer Status und Siderophor-Produktion von Pseudomonas Fluorescens sp. in der Rhizosphäre

In P. fluorescens Pf 2-79RL lux genes are activated by a ribosomal promoter, thus exponential growth is associated with bioluminescence. Starved cells are characterized by a low physiological status and have a longer length of lag after transfer into rich medium than actively growing cells. Due to the coupling of bioluminescence with exponential growth, the length of the lag phase of bioluminescence can be used to assess its physiological status of P. fluorescens 2-79RL. The length of the lag phase of bioluminescence was increased with increasing starvation in vitro. Mycorrhizal infection decreased both population density and physiological status of P. fluorescens 2-79RL in the rhizosphere. In P. fluorescens Pf-5, pyoverdine production is reported by ice nucleation. Thus ice nucleation activity increases with increasing Fe stress. Using this reporter, Fe stress of P. fluorescens Pf-5 was determined in the rhizosphere of barley and rice. Fe-stress was greater in rice than in barley and in barley, foliar Fe treatment increased Fe stress of P. fluorescens Pf-5. By incorporation of the ice reporter into P. fluorescens 2-79RL it is now possible to monitor the physiological status and Fe stress simultaneously. Low N availability reduced population density but increased Fe stress of P. fluorescens 2-79RLI in the rhizosphere of wheat. However, the physiological status was not affected by N-availability.