APPLICATION OF IMAGEJ TO QUANTIFY THE SWEEPING AND BINDING OF PRECIPITATES BY EUGLENA MUTABILIS TO FORM IRON-RICH STROMATOLITES

Euglena mutabilis is a photosynthetic, acidophilic protozoan that forms benthic biofilm and builds Fe-rich stromatolites in acid mine drainage (AMD) channels at the Green Valley coal mine site in Indiana, USA. This study uses microvideography and ImageJ analysis to document and quantify the ability of E. mutabilis to build stromatolites by trapping and binding Fe-rich chemical sediment that form continuously in the AMD system. A slurry mixture of simulated AMD and powdered Al hydroxide was pipetted onto glass slides containing Euglena cells to simulate chemical sedimentation. Microvideography shows that cells used secreted mucilage and a sweeping locomotion to trap particles to the cell surface. These particles were then transported down the sides of the cell to the posterior end to form an accumulating bundle of particles transported behind the cell. Bundles were carried by E. mutabilis to a continually growing centralized mass of particles being reworked by other E. mutabilis cells. ImageJ, a public domain processing and analysis program, was used to quantify spatial clearing of simulated chemical sediments by cells over a period up to 25 minutes. The analysis showed that upon application of the slurry mixture, particles were distributed evenly, where the majority of space was centralized around 50% particles and 50% cleared space. After 25 minutes of binding and remobilization of particles, analysis showed a higher percentage of areas containing completely cleared space and completely dark space (i.e., bound particles), indicating that clearing and clumping had occurred. We propose that the microbial activity of sweeping, gathering, binding, and transport of simulated chemical sediments is a major mechanism used by E. mutabilis to construct biolaminated stromatolites observed in the AMD environment. This study has important implications for understanding microbial activity responsible for forming similar stromatolitic structures on early Earth and for the exploration for similar traces on such extraterrestrial bodies as Mars.