Microbial Profiling: Identifying Unknown Strains of Bacteria and Yeast
Inquiry Framework
Question Framework
Driving Question
The overarching question that guides the entire project.How can we develop a robust diagnostic framework to identify a cryptic microbial isolate, reconciling phenotypic and genomic evidence while accounting for the professional and global stakes of misidentification?Essential Questions
Supporting questions that break down major concepts.- How can we translate invisible biological characteristics and metabolic 'fingerprints' into a definitive taxonomic identity?
- In what ways do classical phenotypic observations and modern genomic data complement or contradict each other when determining microbial phylogeny?
- How does the context of an unknown sample (clinical, environmental, or industrial) dictate the diagnostic pathway and the level of precision required?
- What are the systemic consequences of misidentification in a globalized society, and how do scientists mitigate these risks?
- To what extent do our current classification systems limit or enhance our understanding of microbial diversity and evolution?
Standards & Learning Goals
Learning Goals
By the end of this project, students will be able to:- Demonstrate proficiency in aseptic techniques and classical microbiological methods, including differential staining and biochemical assays, to characterize microbial phenotypes.
- Analyze and interpret genomic sequencing data (e.g., 16S rRNA or ITS regions) using bioinformatics tools and databases to determine phylogenetic relationships.
- Synthesize conflicting or ambiguous data from phenotypic and genotypic sources to formulate a scientifically defensible identification of a microbial isolate.
- Evaluate the ethical, clinical, and industrial implications of microbial misidentification within the context of global health and biosafety.
- Design and document a comprehensive diagnostic workflow that accounts for sample origin and required levels of taxonomic precision.
ASM Curriculum Guidelines for Undergraduate Microbiology
AAAS Vision and Change in Undergraduate Biology Education
Entry Events
Events that will be used to introduce the project to studentsThe Artisan's Sabotage: Crafting a Biological Portfolio
A local artisanal brewery reports that their flagship 'Wild Ale' has changed flavor profile overnight. Students act as bio-consultants tasked with isolating the 'intruder' microbe to determine if it is a dangerous spoilage organism or a unique wild yeast mutation that could be patented and sold.Portfolio Activities
Portfolio Activities
These activities progressively build towards your learning goals, with each submission contributing to the student's final portfolio.The Bio-Detective’s Initial Dossier
In this introductory phase, students act as lead investigators for the brewery. They must first isolate the 'intruder' microbe from the wild ale sample. This activity focuses on mastering aseptic technique, streak-plating for isolation, and performing initial morphological assessments (colony morphology and Gram staining/Microscopy) to establish a baseline 'dossier' for their unknown isolate.Steps
Here is some basic scaffolding to help students complete the activity.Final Product
What students will submit as the final product of the activityA 'Microbial Dossier' containing high-resolution images of the isolated colonies, Gram stain results, and a table detailing colony morphology (color, shape, margin, elevation).Alignment
How this activity aligns with the learning objectives & standardsAligns with ASM 1.3 (diversity and classification) and V&C Core Competency 1 (scientific process). Students begin the identification process by establishing a pure culture and documenting primary morphological characteristics.Metabolic Fingerprinting: Decoding the Secret Life of Microbes
Once the physical appearance is documented, students must probe the 'metabolism' of the intruder. Students will design and execute a battery of biochemical tests (e.g., Catalase, Oxidase, IMViC, API 20E/20NE, or specialized yeast fermentation broths). This activity transforms raw metabolic data into a 'fingerprint' that can be compared against known databases like Bergey’s Manual.Steps
Here is some basic scaffolding to help students complete the activity.Final Product
What students will submit as the final product of the activityA 'Metabolic Fingerprint Map'—a comprehensive chart showing the results of all biochemical assays and a dichotomous key that leads to a probable identification based on these phenotypic traits.Alignment
How this activity aligns with the learning objectives & standardsAligns with ASM 4.1 (metabolic pathways and environmental adaptations) and V&C Core Competency 1. This activity forces students to connect enzyme production and sugar fermentation to specific taxonomic groups.The Silicon Lab: Genomic Blueprinting & Bioinformatics
Physical and metabolic traits can sometimes be ambiguous. In this activity, students extract the genomic 'ID card' of the organism. They will perform a DNA extraction and simulate or analyze 16S rRNA (bacteria) or ITS region (yeast) sequencing data. Using bioinformatics tools like BLAST, students will determine the genetic identity of their isolate and build a phylogenetic tree to see how it relates to known brewery spoilage organisms or beneficial strains.Steps
Here is some basic scaffolding to help students complete the activity.Final Product
What students will submit as the final product of the activityA 'Genomic Blueprint Report' featuring a BLAST result summary (E-values, percent identity) and a phylogenetic tree showing the isolate's evolutionary proximity to related species.Alignment
How this activity aligns with the learning objectives & standardsAligns with ASM 3.4 (molecular tools and bioinformatics). This activity moves students from classical microbiology to modern molecular phylogenetics.The Jury’s Verdict: Reconciling the Evidence
Rarely is science perfectly clear. In this activity, students must reconcile their phenotypic data (what the microbe *does*) with their genotypic data (what the microbe *is*). If the Gram stain suggests one thing and the DNA sequence suggests another, students must investigate why. This mimics real-world diagnostic challenges where mutations or horizontal gene transfer can complicate identification.Steps
Here is some basic scaffolding to help students complete the activity.Final Product
What students will submit as the final product of the activityA 'Comparative Evidence Matrix' and a 2-page 'Final Identification Defense' paper that argues for a specific taxonomic identity based on the weighted strength of all gathered evidence.Alignment
How this activity aligns with the learning objectives & standardsAligns with ASM 1.3 and ASM 3.4. It specifically addresses the learning goal of synthesizing conflicting or ambiguous data from phenotypic and genotypic sources.The Global Risk Assessment: Science in the Hot Seat
The final step of the portfolio asks students to step out of the lab and into the shoes of a consultant. They must evaluate the 'Artisan's Sabotage' scenario: If they misidentified a pathogen as a harmless yeast, what are the legal and health risks? If they misidentified a patentable mutation as a common spoilage organism, what are the economic losses? Students explore the ethics of microbial intellectual property and the public health implications of diagnostic errors.Steps
Here is some basic scaffolding to help students complete the activity.Final Product
What students will submit as the final product of the activityAn 'Impact & Ethics White Paper' formatted as a professional briefing for the brewery owners and local health department officials.Alignment
How this activity aligns with the learning objectives & standardsAligns with ASM 6.3 (impact of microbes on society) and V&C Core Competency 6 (social and ethical implications). This activity connects the technical lab work to the broader professional and global consequences.Rubric & Reflection
Portfolio Rubric
Grading criteria for assessing the overall project portfolioMicrobial Unknown Identification & Global Impact Rubric
Classical Microbiology & Phenotypic Profiling
Assessment of the student's ability to apply classical microbiological techniques to characterize unknown microbial phenotypes.Isolation and Morphological Characterization (ASM 1.3)
The ability to isolate a pure culture through aseptic technique and provide detailed macroscopic/microscopic characterization.
Exemplary
4 PointsDemonstrates flawless aseptic technique with distinct, well-isolated colonies. Macroscopic and microscopic documentation (high-res images) is of professional publication quality. Preliminary hypothesis is supported by robust morphological evidence and taxonomic reasoning.
Proficient
3 PointsSuccessfully isolates the organism with minimal contamination. Documentation is clear and accurate, detailing all required morphological features. Preliminary hypothesis is logical and based on the observed data.
Developing
2 PointsIsolation is partially successful but shows signs of minor contamination. Morphological descriptions are present but lack detail or clarity. Preliminary hypothesis is vague or partially unsupported.
Beginning
1 PointsFailed to isolate a pure culture or documentation is missing significant morphological data. Microscopy results are poor or misinterpreted. Preliminary hypothesis is absent or incorrect.
Metabolic Fingerprinting & Logic (ASM 4.1)
The strategic selection, execution, and interpretation of biochemical assays to create a metabolic profile.
Exemplary
4 PointsAssays are strategically selected based on morphological data. Interpretation shows sophisticated understanding of metabolic pathways, accounting for controls and potential false positives/negatives. Dichotomous key is flawlessly executed.
Proficient
3 PointsSelection of assays is appropriate for the organism type. Results are correctly interpreted and compared to controls. The metabolic fingerprint map and dichotomous key lead to a logical, evidence-based identification.
Developing
2 PointsAssays are selected but may lack a clear diagnostic strategy. Interpretation of results is generally accurate but lacks depth regarding biochemical pathways. Dichotomous key contains minor logical errors.
Beginning
1 PointsAssay selection is arbitrary or insufficient for identification. Interpretation of results is frequently incorrect or ignores control data. Dichotomous key is missing or non-functional.
Molecular Genetics & Bioinformatics
Assessment of the student's ability to utilize molecular tools and databases to study microbial evolution and diversity.Bioinformatics & Phylogeny (ASM 3.4)
Proficiency in using bioinformatics tools (BLAST) and constructing phylogenetic trees to determine genetic identity.
Exemplary
4 PointsDemonstrates advanced mastery of BLAST parameters (E-value, Query Cover, Percent Identity). Phylogenetic tree is professionally formatted, correctly rooted, and provides a sophisticated visualization of evolutionary relationships.
Proficient
3 PointsAccurately interprets BLAST results and identifies the organism to the species/strain level. Phylogenetic tree is correctly constructed and clearly shows the relationship between the isolate and its nearest neighbors.
Developing
2 PointsPerforms BLAST search but shows limited understanding of the significance of alignment scores. Phylogenetic tree is present but contains formatting errors or minor misplacements of taxa.
Beginning
1 PointsFails to correctly identify the organism through genomic data. Bioinformatics summary is incomplete or misinterpreted. Phylogenetic tree is missing or fundamentally flawed.
Critical Thinking & Evidence Synthesis
Assessment of higher-order critical thinking and the ability to navigate ambiguous scientific data.Synthesis and Scientific Argumentation (V&C 1)
The ability to synthesize conflicting phenotypic and genotypic data into a cohesive and scientifically defensible identification.
Exemplary
4 PointsProvides a masterful synthesis of all data, specifically addressing and theorizing reasons for discordant results (e.g., epigenetic factors, horizontal gene transfer). The 'Scientific Defense' is a high-level argument that weights evidence with expert precision.
Proficient
3 PointsSuccessfully reconciles phenotypic and genotypic data. Acknowledges discrepancies and provides plausible scientific explanations for them. The final identification is well-supported by the 'Comparative Evidence Matrix.'
Developing
2 PointsAttempts to reconcile data but may ignore minor discrepancies or provide superficial explanations for conflicting results. The final identification is correct but the supporting argument is thin.
Beginning
1 PointsFails to compare the two data sets effectively. Final identification is either based on only one type of evidence or ignores significant contradictory data. Argumentation lacks scientific rigor.
Professionalism & Societal Context
Assessment of the student's ability to communicate scientific impact and understand the relationship between science and society.Socio-Ethical Impact & Risk Assessment (V&C 6 / ASM 6.3)
Evaluation of the ethical, clinical, and industrial implications of scientific findings in a global context.
Exemplary
4 PointsWhite Paper demonstrates a profound understanding of the 'Precautionary Principle,' SQF standards, and patent ethics. Analysis of misidentification risks is nuanced, considering both local economic and global health impacts. Recommendations are professional and actionable.
Proficient
3 PointsClearly articulates the risks associated with the identified organism in a brewery context. Evaluates the social and ethical implications of the 'Artisan's Sabotage' scenario accurately. Professional briefing format is followed.
Developing
2 PointsIdentifies basic risks but lacks depth in ethical or industrial analysis. Recommendations for the brewery are present but may not fully account for professional standards or the complexity of the scenario.
Beginning
1 PointsFails to connect lab findings to broader societal or ethical consequences. Impact analysis is missing, superficial, or demonstrates a lack of understanding regarding professional scientific responsibility.