Microbiology, Antibiotics and Public Health

Francesca Brescia has obtained her Bachelor’s degree in Biology at the University of Torino in 2013. She decided to continue her studies at the University

of Pavia, where in 2015 she obtained her Master’s degree in Experimental and Applied Biology and, in November 2015, she gained a nine-month research

fellowship about the study of the fungal community associated to different Rubus species. In 2016, she started the doctoral course at the PhD school “Agricultural

Science and Biotechnology” of the University of Udine at the Edmund Mach Foundation of San Michele all’Adige (TN) concerning the interactions between plantassociated

bacteria and biocontrol agents in different nutrient conditions. From August 2018 to February 2019 she was a visiting PhD student at the Technical

University of Vienna (Austria), where she carried out a part of her PhD project studying the compounds produced during microbial interactions.

Statement of the Problem: Bacterial biocontrol agents can improve plant heath with various mechanisms. The

bacterial genus Lysobacter includes different species producing compounds and lytic enzymes active against

phytopathogenic microorganisms and therefore can be a source of new biocontrol agents. In particular, L. capsici

AZ78 (AZ78), isolated from tobacco rhizosphere, effectively controls the causal agent of grapevine downy mildew

(Plasmopara viticola), thanks to the production of antibiotics. Since bacterial communities might modulate the

antibiotic production of biocontrol agents, the aim of this research was to understand if grapevine phyllosphere

bacteria could affect the antibiotic production of AZ78. To test the hypothesis we used a simplified model system

with a culturable phytopathogenic oomycete (Pythium ultimum).

Methodology & Theoretical Orientation: 47 bacterial strains were isolated from leaves of Vitis vinifera L. cv. Pinot

gris and Goldtraminer, identified by 16S rDNA phylogenetic analysis and their impact on AZ78’s inhibitory activity

was assessed in vitro according to the experimental design described in Figure 1.

Findings: Most of the Gram-negative bacterial isolates were γ-Proteobacteria, while the Gram-positive isolates

belonged to Actinobacteria and Firmicutes. None of the isolated strains showed an inhibitory activity against P.

ultimum. Interestingly, most of them promoted AZ78 inhibitory activity. In particular Pseudomonas sp. L35 increased

AZ78 inhibitory activity of the 29.6±0.95%, this can be related to a change in AZ78 gene expression triggered by the

presence of the strain.

Conclusion & Significance: The interaction with the natural microbiota is an important factor to be considered in

evaluating biocontrol agent’s efficacy, because their inhibitory activity can be affected by the microbiota itself. To

gain a full picture, additional studies are necessary, taking into account the plant response, as well as considering the

variation in AZ78 gene expression.