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Colony Grounded SAM2: Zero-shot detection and segmentation of bacterial colonies using foundation models

arXiv cs.CV / 3/17/2026

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Key Points

  • Colony Grounded SAM2 is a zero-shot inference pipeline that detects and segments bacterial colonies without additional training, using foundation models Grounding DINO and SAM2.
  • The model is fine-tuned to the microbiological domain and shows robustness to data changes, achieving a mean Average Precision of 93.1% and a Dice@detection score of 0.85 on out-of-distribution datasets.
  • The authors share the pipeline and weights openly to aid annotation and classification tasks in microbiology.
  • This approach lowers the barrier for automated colony analysis in labs, reducing reliance on labeled datasets and enabling faster microbiology workflows.

Abstract

The detection and classification of bacterial colonies in images of agar-plates is important in microbiology, but is hindered by the lack of labeled datasets. Therefore, we propose Colony Grounded SAM2, a zero-shot inference pipeline to detect and segment bacterial colonies in multiple settings without any further training. By utilizing the pre-trained foundation models Grounding DINO and Segment Anything Model 2, fine-tuned to the microbiological domain, we developed a model that is robust to data changes. Results showed a mean Average Precision of 93.1\% and a Dice@detection score of 0.85, showing excellent detection and segmentation capabilities on out-of-distribution datasets. The entire pipeline with model weights are shared open access to aid with annotation- and classification purposes in microbiology.