Seeing Microbes from the Sky Author: Niko McCarty Published: October 1, 2025 Source: Asimov Press --- Overview This article explores the advancement of biosensors—natural and engineered biological systems that detect environmental signals—and the critical need for improved transducers that can relay biosensor signals over long distances and through barriers. The focus is on a breakthrough method using engineered microbes detectable from drones equipped with hyperspectral cameras, enabling non-invasive, large-scale environmental monitoring. --- Nature’s Biosensors and Human Usage Organisms naturally sense diverse environmental factors: E. coli senses chemical gradients for movement. Birds and moths navigate using magnetic fields and star photons. Mussels monitor water quality by changing shell position, triggering electrical signals as warnings. Humans have leveraged animal biosensors: Pigeons for communication via homing. Dogs for disease and contraband detection. Mussels employed by the city of Poznań, Poland, for water monitoring. Synthetic biology has extracted genes from organisms to create molecular biosensors comprising: Sensors (enzymes, antibodies, or engineered cells) that recognize targets. Transducers that convert detection events into signals (e.g., fluorescence). --- Limitations of Current Biosensors Standard transducers use visible light reporters (GFP, luciferase) that: Require line of sight. Work only at close proximity, often under microscopes. Cannot transmit signals through body tissues or over distance due to poor light penetration. Need for transducers that enable remote and in vivo sensing. --- Breakthrough: Hyperspectral Transducer Technology Bioengineers identified new transducers detectable by: Ultrasound Magnetic Resonance Imaging (MRI) Hyperspectral cameras capable of detecting signals from 90 meters away. Hyperspectral cameras capture hundreds of narrow spectral bands, including UV and near-infrared spectral regions, giving unique “fingerprints” of molecules. Military applications inspired the idea: Hyperspectral drones detect plastic disguised as rocks. Led to the question: can microbes be similarly detected remotely? --- Research Highlights by Yonatan Chemla & Itai Levin Screened hundreds of thousands of biomolecules: Most lacked well-characterized absorption spectra. Tested purified molecules to identify those that produce a clear hyperspectral signature. Used computational quantum chemistry simulations on 20,000 metabolites to predict light absorption profiles. Criteria for selection included ease of microbial biosynthesis. Selected two reporter molecules: Biliverdin IXα produced by Pseudomonas putida (green pigment from heme breakdown). Bacteriochlorophyll a produced by Rhodocyclus gelatinosus (a purple photosynthetic bacterium absorbing near-infrared light). Engineered microbes producing these molecules were sprayed on soil test patches at Fort Devens, MA. Hyperspectral drone cameras successfully detected these microbes from up to 90 meters. --- Challenges and Future Directions Current detection requires microbes to be in direct line of sight on soil surface. Many targets (e.g., pathogens, explosives) lie underground. Researchers are looking for volatile molecules emitted by microbes that diffuse into the air, enabling remote detection from greater heights or even space. --- Regulatory and Commercialization Barriers Field trials of engineered microbes peaked in the early 1990s but declined due to: Stricter regulations. Mixed trial results. Regulatory landscape: EPA, USDA, FDA share jurisdiction based on microbe use. Environmental biosensors fall under EPA's Toxic Substances Control Act (TSCA), which focuses on the engineering method, not the final product's safety.