Hello Pokpong Th,

OmpC is a porin, a type of outer membrane protein crucial for the bacterium's structure and function. The amount of OmpC expressed on the surface of E. coli MG1655 can vary depending on growth conditions. The presence of any mutations or differences in the OmpC protein sequence between the specific antibody used and the target MG1655 strain will also matter. High expression is usually needed for reliable detection. 

You need to confirm that E. coli MG1655 actually expresses OmpC under your laboratory conditions. There are certain OmpC antibodies that are designed to be highly specific to particular serotypes or to differences that might arise from mutations. 

You should use a robust antibody pair that would target common surface proteins that are present across most E. coli strains. A major outer membrane protein that is conserved across many E. coli strains is the OmpA. As far as robustness is concerned, OmpA is an integral part of the outer membrane, making it a stable and consistently expressed target regardless of the bacterium's growth phase or environment. This avoids issues that can arise with antibodies targeting transient or variably expressed antigens. MG1655 has the H18 flagellar antigen. You may also use an antibody pair that could target two different epitopes on the H18 antigen.

Best,

Dear Malcolm Nobre,

Thank you very much for your informative suggestions. I have done some initial follow-up, and here are a few details:

1) Most commercial E. coli OmpA antibodies I have found are designed specifically for E. coli O157:H7. I will discuss with my supervisor before making any purchase.

2) According to the ATCC product sheet, the serotype of MG 1655 is OR:H48:K-. Based on my understanding, I believe its flagellar antigen should be H48, not H18. Could you kindly confirm if I understand correctly?

3) I have not yet confirmed whether OmpC expression is conserved in MG 1655. I plan to consult with a microbiologist in my research group about this point.

Thank you again for your valuable advice. I will be sure to share updates as my work progresses.

Best regards,

Yes, you are right. If the serotype of E. coli MG1655 is OR:H48:K-, its flagellar antigen is indeed H48.

Regards,

For non-pathogenic E. coli strains (like K-12, DH5α, BL21), you can use anti–E. coli polyclonal antibodies from Abcam, Thermo Fisher, or Sigma. If you need conserved markers, antibodies against OmpA, OmpC, or LPS core antigens work well. For intracellular proteins, anti-GroEL or anti-DnaK are reliable. Engineered strains expressing GFP can be detected with anti-GFP antibodies. Choice depends on your application (immunofluorescence, western blot, ELISA, or flow cytometry).