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Public evidence
Escherichia colilacYlacZlacI

Does lower ONPG color mean less LacZ enzyme?

Change

Additional deletion of lacY.

Measured

ONPG hydrolysis, A420 normalized to OD600 over time.

Observed outcome

Adding a lacY deletion to MG1655 ΔlacI reduced basal ONPG hydrolysis relative to MG1655 ΔlacI. Figure 2 shows representative technical triplicates; no effect size is digitized here.

Source 1
System
Escherichia coli · MG1655 ΔlacI versus MG1655 ΔlacI ΔlacY
Setting
Intact-cell chromogenic assay in an existing lacI-deletion background.
Comparison
MG1655 ΔlacI retaining lacY.

What was observed

Checked findings go into your research brief.

2
ObservedSource 1

Adding a lacY deletion to MG1655 ΔlacI reduced basal ONPG hydrolysis relative to MG1655 ΔlacI. Figure 2 shows representative technical triplicates; no effect size is digitized here.

Results: Development of HTS platform; Figure 2A and legend

ObservedSource 1

In the intact-cell ONPG assay, substrate hydrolysis depends on envelope permeability or release of intracellular β-galactosidase through lysis.

Results: Development of HTS platform, opening paragraph; Figure 1

What this supports

Interpretation
  • The readout depends on substrate access as well as enzyme activity.
What this does not establish
  • Lower color alone does not establish reduced lacZ transcription, less LacZ protein, or enzyme inactivity.
Gene location & edit specificity

No exact edit interval established by this evidence review.

lacY · MG1655 reference

Same gene, different setting

Compare the contexts before carrying a finding across them.

Does deleting lacZ stop growth?Escherichia coli · MG1655-derived NCM3384 and NCM3387
The strain changes what “lacZ” meansEscherichia coli · BW25113, DH5α KAIST stock, and NEB 5-alpha

Sources

Reviewed Sep 26, 2026
1A High-Throughput Approach To Identify Compounds That Impair Envelope Integrity in Escherichia coli2016 · Peer-reviewed experiment
Reviewed
Selected full-text sections
Sections
Results: Development of HTS platform to measure E. coli envelope integrity · Figure 2A and legend · Table 1
DOI
10.1128/AAC.00537-16
resulting in a significantly lower rate of ONPG hydrolysis
Results: Development of HTS platform, lacY-deletion paragraph
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