Part:BBa_K4342001

ACIAD2049 Upstream

File:IGEM - tdk-kan-selection.png

The insertion of the tdk/kan cassette in place of a target gene (ACIAD2049).

File:IGEM - tdk-kan-counterselection.png

The scarless deletion of the tdk/kan cassette produced by BsmBI digestion.

Introduction

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Usage and Biology

ACIAD2049 is a nonessential gene in Acinetobacter baylyi ADP1 [1]. Knocking out this gene allows for the integration of other DNA sequences in its chromosomal location. Cooper et al. have taken advantage of the ACIAD2049 gene deletion to create ADP1-based biosensors capable of detecting diseases within the human body [1]. Using this part, we demonstrate that ACIAD2049 knockouts can be used to detect antibiotic resistance genes using ADP1 as a chassis organism.

Design

The ACIAD2049 Upstream part comprises the 1292 bp homology directly upstream of the ACIAD2049 gene in ADP1. This specific region was chosen to create optimized primers, which include GC contents of over 40% and melting temperatures of under 70 °C. Restriction sites are attached to the 3’ end, which are specifically designed to allow for ligation to the tdk/kan selection cassette (BBa_K4342000). This composite part, BBa_K4342019, then allows for the deletion of the ACIAD2049 gene via our ADP1 Golden Transformation protocol, found on this page.

This part contains a BsaI restriction site with a standard 4 bp GGA Type 2 Prefix and a BsmBI restriction site with a 4 bp “rescue” complementary scar. See the Contribution page for more details on GGA Type Overhangs. This design allows for easy ligation with any part that contains a complementary 4 bp GGA Type 2 Prefix (BsaI) or the same 4 bp “rescue” complementary scar.

Composite Parts

This basic part can be assembled to create composite parts using the BsaI restriction site, which can be then used to integrate the tdk/kdan cassette in place of the ACIAD2049 gene (Fig. 1). Or, BsmBI digestion can be used with this part to create scarless deletions of the ACIAD2049 gene (Fig. 2).

BsaI Restriction Site

This part is designed to ligate to the 5' end of the tdk/kan cassette, BBa_4342000, creating the ACIAD2049 tdk/kan cassette composite part (BBa_4342019). This composite part allows for successful transformant selection on Kanamycin (Kan) via the kanR gene (Fig. 1).

BsmBI Restriction Site

The tdk/kan cassette can subsequently be knocked out to create a scarless deletion of ACIAD2049 via BsmBI digestion, BBa_4342020. During this reaction, this part is ligated to the 5' end of the ACIAD2049 Downstream part BBa_4342002. This composite part serves as a “rescue” cassette to select for successful transformants on Azidothymidine (AZT) (Fig. 2).

Characterization

To confirm that we successfully created this part, we performed a PCR and gel electrophoresis using genomic DNA from the ADP1-ISx strain as a template. Bands were visible at ~1300 bp, confirming the amplification of the ACIAD2049 Upstream part. A PCR master mix with water in place of template DNA was used as negative control.

References

[1] Cooper, R. M., Wright, J. A., Ng, J. Q., Goyne, J. M., Suzuki, N., Lee, Y. K., Ichinose, M., Radford, G., Thomas, E. M., Vrbanac, L., Knight, R., Woods, S. L., Worthley, D. L., & Hasty, J. (2021). Engineered bacteria detect tumor DNA in vivo. bioRxiv. https://doi.org/10.1101/2021.09.10.459858.