Colony vs. Plaque Hybridization: Key Differences in DNA Screening Techniques
Colony hybridization screens intact bacterial colonies on agar; plaque hybridization screens viral plaques in a bacterial lawn. Both use labeled DNA probes to fish out desired sequences from thousands, but they target different biological formats.
Lab memos often say “screen the colonies” even when referring to phage plaques—Petri dishes look alike under the hood, and both techniques share probe cocktails, so names blur in day-to-day chatter.
Key Differences
Colony: intact cells on a membrane, 0.5–1 mm spots, survives lysis for plasmid DNA. Plaque: clear holes in a bacterial lawn, 1–3 mm, viruses released after cell lysis. First uses alkali lysis; second skips it, lysing occurs naturally.
Which One Should You Choose?
Plasmid library? Pick Colony hybridization. Lambda or M13 phage library? Go Plaque hybridization. Your choice is dictated by the vector, not personal preference.
Examples and Daily Life
Imagine hunting an antibiotic-resistance gene: spread E. coli transformants on agar, press a membrane, probe—Colony. Now hunt the same gene in a phage display library—pour top agar with host cells, let plaques form, probe—Plaque.
Can one membrane be reused?
No; stripping destroys bacterial DNA or viral plaques, so always use a fresh replicate.
Do both need radioactivity?
Nope. DIG or fluorescent probes work for either, keeping benches safer.
Is colony PCR faster?
For small batches, yes, but it skips clone verification after hybridization.