*2.2. Bioactivity Assessment—Microbroth Dilution Assays*

In order to determine the antimicrobial potency, the generated extracts were screened against a diverse panel of pathogenic microorganisms including *Escherichia coli* ATCC35218, *Staphylococcus aureus* ATCC33592, *Pseudomonas aeruginosa* ATCC27853, as well as *Candida albicans* FH2173 and the phytopathogenic fungus *Septoria tritici* MUCL45407. In total, seven of the 76 tested sponge extracts exhibited growth inhibitory effects of at least 85% across 3 dilution steps against one or more test strains and were thereby considered bioactive: Essentially, samples KOL\_8, KOL\_16, KOL\_18, and ULU\_13 were active against *S. aureus*, *C. albicans*, and *S. tritici*, PEHE\_5 against *S. aureus* and *S. tritici*, and extracts PANIKI\_4 and ULU\_16 showed activity only against *S. tritici*. In addition, two extracts (ULU\_11 and ULU\_17) showed weak activity against *C. albicans* by inhibiting the cell viability of the test strain only in the highest concentrations. No growth inhibition of the selected Gram-negative test strains was observed.
