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Public evidence
Escherichia colilacZlacY

Does a lacZ deletion prevent E. coli growth, or does the carbon source change the conclusion?

Change

ΔlacZ39 in MG1655-derived NCM3387.

Measured

Culture doubling time, minutes.

Observed outcome

The MG1655-derived ΔlacZ strain NCM3387 and its comparator NCM3384 each had a reported doubling time of 110 min on galactose plus IPTG.

Source 1
System
Escherichia coli · MG1655-derived NCM3384 and NCM3387
Setting
Defined medium; galactose plus IPTG. Glycerol plus IPTG was a separate control condition.
Comparison
NCM3384, the study's matched lac wild-type comparator, not an unmodified stock of every MG1655 strain.

What was observed

Checked findings go into your research brief.

2
ObservedSource 1

The MG1655-derived ΔlacZ strain NCM3387 and its comparator NCM3384 each had a reported doubling time of 110 min on galactose plus IPTG.

Table 5, NCM3384 and NCM3387 rows, Galactose + IPTG column

Measurement details
Reported value
110 min doubling time
Group
NCM3384 and NCM3387; galactose + IPTG
ObservedSource 1

The MG1655-derived ΔlacZ strain NCM3387 and its comparator NCM3384 each had a reported doubling time of 100 min on glycerol plus IPTG.

Table 5, same rows, Glycerol + IPTG column

Measurement details
Reported value
100 min doubling time
Group
NCM3384 and NCM3387; glycerol + IPTG

What this supports

Interpretation
  • No doubling-time difference was reported in these two comparisons.
What this does not establish
  • This is not a lactose-only growth experiment or evidence that every lacZ change is neutral.
Gene location & edit specificity

Reference gene interval

NC_000913.3:363231–366305 (-)

NCBI annotated lacZ interval, 1-based inclusive; not the experimentally verified ΔlacZ39 boundaries or a recommended edit site.

Reference gene located; exact perturbation boundaries not mapped here.

lacZ · MG1655 reference

Same gene, different setting

Compare the contexts before carrying a finding across them.

A weaker reporter can mean less substrate accessEscherichia coli · MG1655 ΔlacI versus MG1655 ΔlacI ΔlacY
The strain changes what “lacZ” meansEscherichia coli · BW25113, DH5α KAIST stock, and NEB 5-alpha

Sources

Reviewed Sep 26, 2026
1Physiological Studies of Escherichia coli Strain MG1655: Growth Defects and Apparent Cross-Regulation of Gene Expression2003 · Peer-reviewed experiment
Reviewed
Selected full-text sections
Sections
Table 1 strain definitions · Table 5 and footnote · Results paragraphs accompanying Table 5
DOI
10.1128/JB.185.18.5611-5626.2003
Only the strain with the (polar) lacY mutation grew slowly
Results paragraph immediately before Table 5
Read the source
2NCBI Gene: lacZ, MG1655, b03442026 · Reference annotation
Reviewed
Reference record
Sections
Genomic context · Reference assembly NC_000913.3
Read the source