Biofilms are ubiquitous, easy to grow and quantify, and provide useful systems for improving student learning of scientific methods. Biofilms were the focus of a semester-long scaffolded laboratory activity for upper-level biology and biochemistry majors. Shorter interspersed activities were used to introduce procedures so that the biofilm project served as a summative assessment of learning. There were five outcomes: 1) locate and summarize primary scientific literature about biofilms, 2) develop hypotheses and predictions to answer a scientific question, 3) design an experiment to test hypotheses and predictions, 4) analyze and present data in scientific format, and 5) present results in a written scientific report. The activity was scaffolded into four parts. For the first part individual students used scientific literature to identify variables impacting formation and/or growth of microorganisms as biofilms. For each variable they wrote a one-page summary of their learning. The remaining three parts of the activity were completed by pairs of students working collaboratively. For part two each pair submitted a proposal for a scientific experiment that contained an introduction to the question they proposed to investigate, accompanying hypothesis and prediction statements, detailed methods for completing the experiment, and a graph showing the data if the prediction was correct. Part three was a description of the experimental data analysis and results. Part four was a written description of the entire project in complete scientific format. Escherichia coli or Staphylococcus epidermidis biofilms were grown in 96-well plates and density was measured by staining with safranin, which was eluted and quantified as absorbance with a plate reader. Achievement of all five learning outcomes were measured on scoring rubrics with four levels: achieved, competent, developed, and initiated. Median scores calculated for n=10 (outcome 1) or n=5 (outcomes 2-5) indicated a majority reached competent or achieved levels for all outcomes.
