AUTHOR=Alsanius Beatrix W. , Vaas Lea , Gharaie Samareh , Karlsson Maria E. , Rosberg Anna Karin , Wohanka Walter , Khalil Sammar , Windstam Sofia 

TITLE=Dining in Blue Light Impairs the Appetite of Some Leaf Epiphytes

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.725021

DOI=10.3389/fmicb.2021.725021

ISSN=1664-302X

ABSTRACT=<p><bold>Background:</bold> The phyllosphere is subjected to fluctuating abiotic conditions. This study examined the phenotypic plasticity (PP) of four selected non-phototrophic phyllosphere bacteria [control strain: <italic>Pseudomonas</italic> sp. DR 5-09; <italic>Pseudomonas agarici</italic>, <italic>Bacillus thuringiensis</italic> serovar <italic>israeliensis</italic> (Bti), and <italic>Streptomyces griseoviridis</italic> (SG)] regarding their respiration patterns and surfactant activity as affected by light spectrum and nutrient supply.</p><p><bold>Methods:</bold> The PP of the strains was examined under four light regimes [darkness (control); monochromatic light-emitting diodes (LED) at 460 nm (blue) and 660 nm (red); continuously polychromatic white LEDs], in the presence of 379 substrates and conditions.</p><p><bold>Results:</bold> Light treatment affected the studied bacterial strains regarding substrate utilization (<italic>Pseudomonas</italic> strains &gt; SG &gt; Bti). Blue LEDs provoked the most pronounced impact on the phenotypic reaction norms of the <italic>Pseudomonas</italic> strains and Bti. The two Gram-positive strains Bti and SG, respectively, revealed inconsistent biosurfactant formation in all cases. Biosurfactant formation by both <italic>Pseudomonas</italic> strains was supported by most substrates incubated in darkness, and blue LED exposure altered the surface activity profoundly. Blue and white LEDs enhanced biofilm formation in PA in highly utilized C-sources. Putative blue light receptor proteins were found in both <italic>Pseudomonas</italic> strains, showing 91% similarity with the sequence from NCBI accession number <ext-link ext-link-type="DDBJ/EMBL/GenBank" xlink:href="WP_064119393" xmlns:xlink="http://www.w3.org/1999/xlink">WP_064119393</ext-link>.</p><p><bold>Conclusion:</bold> Light quality–nutrient interactions affect biosurfactant activity and biofilm formation of some non-phototrophic phyllosphere bacteria and are, thus, crucial for dynamics of the phyllosphere microbiome.</p>