How do they prevent the E. Chromi bacteria from eventually being displaced by other non color coding poo bacteria? It seems to me that even if the E. Chromi did work as advertised, that the bacteria would quickly (within days) disappear from your intestinal track.
If anything, I would suspect that the E. Chromi would be at an evolutionary disadvantage in the gut. This is because the E. Chromi would be expending effort trying to color code poo, while their neighboring bacteria would just be focused on digesting and reproduction. Based on the principles of evolution, I would expect the E. Chromi bacteria to disappear entirely from the gut with a few thousand generations of bacteria.
Very important point. E. coli describes a range of organisms that share about 14% of their genome. For comparison, all of primates share over 99%. The strains everyone uses for genetic engineering are derived from strains isolated many decades ago and are incapable of colonizing hosts. They've also been selected over the years to be hysterical (they over respond to any stimulus, since when you're picking colonies to study response, you select the bright, clear one...and if you do it again and again over the years, you select for hysteria).
Poking around, I couldn't find the strain they used. They might have engineered a gut isolate. They might not. Doesn't appear to say anywhere.
If anything, I would suspect that the E. Chromi would be at an evolutionary disadvantage in the gut. This is because the E. Chromi would be expending effort trying to color code poo, while their neighboring bacteria would just be focused on digesting and reproduction. Based on the principles of evolution, I would expect the E. Chromi bacteria to disappear entirely from the gut with a few thousand generations of bacteria.