11.1.2 Culture Vessel and Culture Conditions
The culture vessel and culture conditions were similar to those used in the microcosm N-system. A 300 mL Erlenmeyer flask was used, and the conditions included a
temperature of 25
C and an illuminance of 2400 lux, with an L/D cycle of 12 h each.
11.2 Mathematical Simulation
Differential equations were developed to simulate the dynamics of a batch culture
microcosm that was composed of the bacterial decomposer, Pseudomonad putida;
the protozoan consumer, Cyclidium glaucoma; and the chlorophyte producer, Chlorella vulgaris. Two different types of equations were examined. One was an
equation that accounts for the metabolites of microbes, and the other was an equation
that does not account for them. The results of the simulation were compared with the
empirical data obtained from the substrate-one species and substrate-two species
subsystems and from the microcosm N-system. It was shown that the differential
equations with the variables for the metabolite and a lack of protozoan predation on
bacteria corresponded better with the empirical data than did the equations without
these variables. Therefore, it was suggested that the promotion and inhibition of
microbial growth by each metabolite and the existence of non-predated bacteria by
protozoans were important to the dynamics of a batch culture microcosm.
The population dynamics of genetically engineered microorganisms (GEMs) in a
microcosm were also analyzed using computer simulations. The GEM Escherichia
coli HB101/pBR325 model was inoculated into the microcosm containing the alga,
Chlorella vulgaris; the bacterium, Pseudomonas putida; and the protozoan,
Cyclidium glaucoma, 14 days after cultivation of the microcosm was initiated.
When the model GEMs were added at 10
8 cells/mL (high density), protozoans
multiplied and then decreased rapidly. The same population density was recovered
as that in the microcosm without the addition of the model GEM. The model GEM
also rapidly decreased until it leveled out at a density of ~10
4 cells/mL when
protozoan abundance increased. Conversely, in the microcosm into which model
GEMs were added at 10
4 cells/mL (low density), the population density of neither
the indigenous bacteria nor the model GEM changed. Based on empirical data, a
differential equation that represents the indigenous bacterial and model GEM population dynamics was developed and solved. The simulation corresponded well with
the empirical data. However, there was a difference between the high- and
low-density introductions of the model GEM in the various parameters, representing
the exchange of bacteria between the predated model GEM and the non-predated
model GEM by protozoans. This indicates that the values of parameters changed
when the model GEM aggregated or when a cellular morphological change of the
model GEM occurred.
196
Y. Inamori et al.
The culture vessel and culture conditions were similar to those used in the microcosm N-system. A 300 mL Erlenmeyer flask was used, and the conditions included a
temperature of 25
C and an illuminance of 2400 lux, with an L/D cycle of 12 h each.
11.2 Mathematical Simulation
Differential equations were developed to simulate the dynamics of a batch culture
microcosm that was composed of the bacterial decomposer, Pseudomonad putida;
the protozoan consumer, Cyclidium glaucoma; and the chlorophyte producer, Chlorella vulgaris. Two different types of equations were examined. One was an
equation that accounts for the metabolites of microbes, and the other was an equation
that does not account for them. The results of the simulation were compared with the
empirical data obtained from the substrate-one species and substrate-two species
subsystems and from the microcosm N-system. It was shown that the differential
equations with the variables for the metabolite and a lack of protozoan predation on
bacteria corresponded better with the empirical data than did the equations without
these variables. Therefore, it was suggested that the promotion and inhibition of
microbial growth by each metabolite and the existence of non-predated bacteria by
protozoans were important to the dynamics of a batch culture microcosm.
The population dynamics of genetically engineered microorganisms (GEMs) in a
microcosm were also analyzed using computer simulations. The GEM Escherichia
coli HB101/pBR325 model was inoculated into the microcosm containing the alga,
Chlorella vulgaris; the bacterium, Pseudomonas putida; and the protozoan,
Cyclidium glaucoma, 14 days after cultivation of the microcosm was initiated.
When the model GEMs were added at 10
8 cells/mL (high density), protozoans
multiplied and then decreased rapidly. The same population density was recovered
as that in the microcosm without the addition of the model GEM. The model GEM
also rapidly decreased until it leveled out at a density of ~10
4 cells/mL when
protozoan abundance increased. Conversely, in the microcosm into which model
GEMs were added at 10
4 cells/mL (low density), the population density of neither
the indigenous bacteria nor the model GEM changed. Based on empirical data, a
differential equation that represents the indigenous bacterial and model GEM population dynamics was developed and solved. The simulation corresponded well with
the empirical data. However, there was a difference between the high- and
low-density introductions of the model GEM in the various parameters, representing
the exchange of bacteria between the predated model GEM and the non-predated
model GEM by protozoans. This indicates that the values of parameters changed
when the model GEM aggregated or when a cellular morphological change of the
model GEM occurred.
196
Y. Inamori et al.