Root Microbiology
Short introduction to PhD thesis:
Interactions of biofilm-forming human pathogenic bacteria with plant roots
The fact that the rhizosphere of plants could be a natural habitat for human pathogenic bacteria was for a long time underestimated. Plants can be colonized on various surfaces as well as endophytically by human pathogenic or toxin-producing bacteria. These microorganisms are often closely related to strains, which entail essential benefits for plants (PGPR), without being of any concern to the health of animals or humans. Human pathogenic bacteria and toxin-secreting bacteria can be introduced into soils by e. g. agricultural practices like application of contaminated slurry or of residues from fermentation plants, and subsequently cultivate the rhizosphere of crop plants. If the bacteria exhibit the ability for endophytic colonisation there is a risk for a systemic colonization of the plant by potential pathogens, which are then also present in the consumed parts of the plant. Directly or via the food chain these pathogenic germs could be transmitted to animals and human beings.
Indeed, in the last years a continuous increase in diseases of human beings was detected, which could be traced back to for example the consumption of microbiologically contaminated vegetable. Possible opportunistic human pathogenic bacteria include Ochrobactrum spp., Stenotrophomonas spp., Roseomonas spp., Cronobacter spp., Klebsiella spp., as well as Gram-positive microorganisms like Staphylococcus, Streptococcus, Clostridium spp. or Bacillus spp.
As an example for a high-risk toxin-producing bacterium, Clostridium botulinum derived from deployed fermentation remainders, will be focused on its colonisation and interaction with forage crops. By means of in situ-localisation experiments (FISH, GFP-marker) the efficiency of the colonisation of the roots will be investigated. Additional methods including specific PCR-verifications and cultivations are projected. By the use of genomic comparison of human pathogenic bacteria with closely related saprophytic or even growth-promoting bacteria (PGPR) crucial differences between these pathogenic and benign bacteria will be identified and functions of genes relevant for biofilm-forming analysed.
