Since the bacteria enter the human intestine in the form of distribution in a liquid, it should enter the intestines for a period of time slowly, we have made reasonable assumptions about the duration and amount of time and amount of food into the intestines.
For the movement of engineered bacteria in the intestines, we took into account factors such as E. coli moving with the eating palate and being driven by the oil attached to the surface of the intestine.
For safety reasons, E. coli intake needs to be excluded from the body for a certain period of time, and we assume that E. coli will be excluded over time by focusing on the end of the intestine waiting for the body to defecate. A suicide switch is also designed that, due to the relatively high concentration of oxygen outside, will trigger a suicide switch for the engineered bacteria, which in turn will kill E. coli.
The distribution image can better reflect the relative distribution of E. coli in the intestine during this period. Considering the amount of engineered bacteria consumed, the distribution function of the model can only indicate the relative amount of E. coli ingested in various parts of the intestine, while the absolute amount of E. coli is positively correlated with the intake of E. coli.
The distribution image also reflects that after a short period of time, the vast majority of engineering bacteria will be excreted, will not affect the body.
% is time in 10s and in 10mm intervals
%simulation predicts the distribution of E. coli populations over time within each interval
% assuming an initial E. coli population of 1 million
%2000ml liquid enters the digestive tract, where saliva 250ml, stomach fluid 500ml, bile 250ml, pancreatic fluid 500ml, food and drinking water 500ml
%90% of the liquid is absorbed in the small intestine and 8.5% of the liquid is absorbed in the large intestine
%Assuming that E. coli is evenly distributed in its initial state and that E. coli is attached to the diet, its position movement will not be affected by the absorption of moisture in the small intestine %
% liquid amount is calculated
T1 = zeros(3600,750);
U1 = 1000;
T1(1,1) = 1;
for i = 2:3600
T1(i,750) = T1(i-1,750)+T1(i-1,749)*0.8;
T1(i,749) = T1(i-1,750)+T1(i-1,749)-1;
T1(i,750) = 1;
for j = 749:-1:701
sum1 = T1(i-1,j)*0.2+T1(i-1,j-1)*0.8;
sum1 = T1(i-1,j)+T1(i-1,j-1)*0.8;
T1(i,j-1) = T1(i-1,j)+T1(i-1,j-1)-1;
T1(i,j) = 1;
T1(i,j) = sum1;
for j = 700:-1:601
T1(i,j) = T1(i-1,j)*0.2+T1(i-1,j-1)*0.8*(1-1/((100/0.85)-(j-600)));
for j = 600:-1:2
T1(i,j) = T1(i-1,j)*0.2+T1(i-1,j-1)*0.8*(1-1/(600/0.9-(j-1)));
T1(i,1) = T1(i-1,1)*0.2;
T1(i,1) = T1(i,1)+0.8;
U1 = U1-0.8;
T1(i,1) = T1(i,1)+U1;
U1 = 0;
% Randomly simulates the lining oil of the intestine
Y1 = 5+5*rand(1,600);
Y2 = 5*rand(1,150);
Y3 = [Y1 Y2];
sumY = 0;
for i = 1:750
sumY = sumY+Y3(i);
Y = Y3/sumY;
%Simulated engineering bacteria move with liquids and greases
T2 = zeros(3600,750);
for i = 1:3600
for j = 1:750
T2(i,j) = T1(i,j)*Y(j)*10000;
% image display
for i = 1:3
for i = 4:6
a) The mazF by the lac promoter, while the lac promoter strength is related to the lactose concentration in the environment.
b) The mazE is regulated by the phyb promoter, and the phyb promoter is regulated by the oxygen concentration
2. We neglect the effects of dilution/ growth. We thus assume the cell’s volume to be constant over time.
3. Ignore the effects of translation regulation in this process.
Figure. Suicide design
Figure. the Suicide model
Table. 1 ODEs used in model
Table. 2 Symbol interpretation
 Modeling E.coli Tumbles by Rotational Diffusion Implications for Chemotaxis, PLOS one, by Jonathan Saragosti, Pascal SilBerzran, Axel Buguin
 E. coli in Motion, Springer, by Howard C. Berg
 Directional persistence of chemotactic bacteria in a traveling concentration wave, PNAS, by J. Saragosti, V. Calvez, N. Bournaves, B. Perthame, A. Buguin, and P. Silberzan