I found this on a webpage (http://openwetware.o..._coli_genotypes): dcm = cytosine methylation at second C of CCWGG sites exist. dam & dcm are the default properties and always elided, while dam- or dcm- should be declare explicitly
Now, when reading this I understand that dcm is always present in cells and when its not present in a certain strain it should be noted with dcm- , but when I look at certain strains, it always says: dcm (without the -) does this mean that dcm is present in these strains? Which is weird, since they state its always present ? Or does it mean that its absent? (which would make more sense because they only seem to mention "things" when its absent or mutated)
But the website also states this: coli B strains are naturally lon- and dcm- , does this mean that all B strains are dcm- and this the dcm- part is not mentioned anymore? And when its mentioned, it means its present?? This makes it pretty confusing.
When I look at those B strains it says for example: BL21
E. coli B F- dcm ompT hsdS(rB- mB-) gal [malB+]K-12(λS)
Does this mean dcm is not present or does it mean it is present? Either way, its confusing since they dont use the dcm- and since its a B strain, its automatically not present?
Especially because another B strain (that should not have dcm) is given like this: B2155
thrB1004 pro thi strA hsdsS lacZD M15 (F`lacZD M15 lacIq traD36 proA+ proB+) D dapA::erm (Ermr) pir::RP4 [::kan (Kmr) from SM10]
It does not mention dcm anymore? So dcm is present is this strain or not?
A last question: whats the difference betwen () and  when used in strain genotypes? sometimes I see (...) and [...] in a strain , but what does it mean? for example:
B F- ompT hsdS(rB- mB-) metA::Tn5(kanr)
Tetr gal λ (DE3) endA Hte [argU proL Camr]
Edited by lyok, 11 August 2012 - 01:44 AM.