Application Study: Bacterial-Fungal Competition

Objective

Investigate competition dynamics between Bacillus subtilis and filamentous fungi.

Introduction

Inhibition assays have broad applications from testing microbial candidates for bioprotection of food products to evaluating potential agricultural biocontrol agents. This study employed a classic antagonistic setup to examine competition between a Bacillus subtilis strain and filmentous fungi (Fusarium oxysporum and Penicilium roqueforti). The Reshape Imaging System combined with automated growth analysis facilitated continuous monitoring of microbial interactions.

Results

Reshape Technology enable CFU detection. Bacteria and fungal species were co-cultivated on solid medium to assess the interspecies competition for nutrients and growth niche. The growth of the bacterial and fungal CFU’s were recorded using the Reshape Imaging System, while AI-powered models enabled automated detection and growth analysis (Fig. 1).

Automated analysis of bacterial and fungal growth. Reshape’s automated analysis of the F. oxysporum and B. subtilis competition revealed a larger colony expansion and faster plate colonization by the fungus compared to bacterium (Fig. 2).

_{Figure 2. Monitoring CFU growth. Bacterial and fungal suspensions were inoculated at fixed distance on a plate and incubated with imaging at 30 min intervals in the Reshape Imaging System.}

Bacterial inhibition of fungal growth. Comparison of the challenged fungal growth to the respective fungal controls showed that F. oxysporum and P. roqueforti are restricted by the presence of B. subtilis (Fig. 3).

_{Figure 3. Fungal growth challenged by B. subtilis. Left: Growth timelapse of F. oxysporum or P. roqueforti challenged by B. subtilis. Right: fungal growth timelapse in absence of the bacterium. The species were co-cultivated on potato dextrose agar medium for 7 days and the growth recorded every 30 min.}

Continuous imaging allows timepoint comparison. Comparison at selected timepoints revealed inhibition of both fungal species by B. subtilis after 120h (Fig. 4). Notably, the bacterium exerted a more pronounced growth inhibition on P. roqueforti than F. oxysporum by day 7.

Conclusion

This study underscores the inhibitory capacity of Bacillus subtilis on fungal growth, providing valuable insights into microbial competition dynamics. The Reshape Imaging System, coupled with automated growth analysis, emerges as a powerful tool for unraveling complex microbial interactions in real-time.

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