School of Engineering and Science - Jacobs University

Results
A-E represents single inoculations with A: Psg1a; B: Pss22d; C: Pss22d∆Pvd; D:
Pss22d∆Ach, and E: Pss22d∆Sid. F-I showed the results for co-inoculation
experiments of Psg1a in combination with F: Pss22d; G: Pss22d∆Pvd; H:
Pss22d∆Ach; I: Pss22d∆Sid. In the co-inoculation experiments, antagonist and
pathogen were mixed at a ratio of 2:1. Symptom development was investigated
14 days post inoculation (Fig.23). Only when a single inoculation of Psg1a was
applied, a clear formation of chlorosis could be observed (Fig.23A). Wounds
inoculated with the antagonistic strains alone symptom-free (Fig.23B-E). Wounds
co-inoculated with antagonist and pathogen showed mostly no symptoms, while
on some single wounds a strongly reduced symptom development could be
observed (for example Fig.23G, uppermost wound).
Determination of CFU per wound did not give any evidence for a different
performance of Pss22d wild type and its siderophore mutants. Therefore data
were grouped in Figure 24. In the co-inoculation experiments, pathogen
population size was reduced by one order of magnitude as compared to the
single inoculation of Psg1a. Since wound inoculation technique could potentially
interfere with the impact of siderophores due to a possible iron leakage from
wound exudates, the in planta epiphytical fitness of Pss22d and its siderophore
mutants was investigated in a spray inoculation experiment. Preliminary results
indicated a reduction of population size for the siderophore mutants as compared
to the wild type (Tab. 10). While both single mutants reached a cell density one
order of magnitude below the wild type, the double mutant was reduced by two
orders of magnitude. A repetition of this experiment showed a very similar
outcome for Pss22d∆Pvd; however, growth of Pss22d∆Sid was reduced only by
one order of magnitude and that of Pss22d∆Ach was not affected at all.
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