I was growing a chemical tolerant bacteria(Xanthomonas) on Nutrient agar vs Nutrient agar amended with copper. The bacteria is growing as its supposed to be on NACopper but very few or no growth on NA only. The bacteria is always maintained on media amended with copper. The chemical tolerance is not plasmid borne, so I was keeping out the plasmid addiction from my first guess.
Given that copper is an essential mineral nutrient used by many enzymes, it is likely your species is more reliant on pathways that use copper containing enzymes.
Phil Geis Robert Adolf Brinzer I understand that the term "chemical" was a vague term but it was for wider audience. Also, I mentioned copper later to remove confusion.
Thank you for the inputs. The isolate was growing just fine on media with or without copper. But in a period of time, maybe it became copper dependent. I thought it can be due to media problem or experimental error, so I plated other known bacteria together and they are just fine.
Please don't compromise your science - design, execution or communication - to serve the ignorance of a wider audience who would have nothing technical to offer re. the phenomenon.
Your observation appears phenomenal as copper is largely toxic above background levels. There is some comment to copper dependency in this review Article Copper uptake and resistance in bacteria
What concentration are you using to grow the dependent isolate?
Phil Geis The pathogen we are working is Xanthomonas arboricola pv. pruni. We use 200ppm of CuSO4.5H20 as a threshold to consider resistant (if grows above 200ppm) or tolerant (at or below 200 ppm). This concentration varies widely with other pathovars of Xanthomonas. The one that are resistant has plasmid and the one which are tolerant has only chromosomal copper homeostatis genes.
Its interesting how quickly those chromosomal genes mutated or do not even have genes to store copper for copper dependent pathways (considering this is a major factor). I guess it would be nice to sequence this isolate and see the changes in those genes compared to other copper tolerant isolates as a first step.