Whats the difference between TOP10 and JM109 Ecoli strains? Is that the TOP10 able to express GFP tagged protein and can be visualized under blue light if we are doing cloning, then what makes it let express GFP tagged protein compared to JM109?
There are many genes in bacteria which influence the ability to successfully transfect them with a plasmid carrying foreign DNA and have a high level of expression of a protein encoded by a gene on the plasmid. Some of the important gene families involved are the methylation/restriction genes which are aimed at destroying any DNA seen as "foreign" to the E. coli. Some are involved in controlling plasmid copy number. Some are genes for proteases or protein export pathway proteins which affect how much of the protein is excreted from the E. coli or chopped up and destroyed within the bacterial cell.
JM109 genotype:
Genotype: endA1, recA1, gyrA96, thi, hsdR17 (rk–, mk+), relA1, supE44, λ–, Δ(lac-proAB), [F´, traD36, proAB, lacIqZΔM15], lDE3.
TOP10 genotype:
F- mcrA Δ( mrr-hsdRMS-mcrBC) Φ80lacZΔM15 Δ lacX74 recA1 araD139 Δ( araleu)7697 galU galK rpsL (StrR) endA1 nupG
https://blog.addgene.org/plasmids-101-e-coli-strains-for-protein-expression
https://www.thermofisher.com/order/catalog/product/C404003
https://www.promega.com/products/cloning-and-dna-markers/bacterial-strains-and-competent-cells/bacterial-strain-jm109_de3_/?catNum=P9801
without knowing how your GFP is being expressed and whether there is something about one genotype that affects that system, it is hard to say anything with certainty. But in general I would think you should see adequate GFP expression in both. One major difference though is that JM109 carries lacIq allele so over expresses lac repressors and TOP10 does not, so if your plasmid is being driven by a lac I regulated promoter that could be the difference. Try adding IPTG to the JM109 cultures.
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