influence on the structure and function of the ecosystem was examined. This strain
has Sm
r and Rf
r as markers. Bacillus thuringiensis subsp. aizawai KH rapidly
decreased at 1, 10, or 100 times inoculation concentrations in viable counts using
the selective media method, following microcosm inoculation, and the abundance of
microorganisms (in particular, its primary consumer, the protozoan ciliate,
Cyclidium glaucoma) in the microcosm increased. Bacillus thuringiensis subsp.
aizawai KH has shown to be a suitable food source for constituent heterotrophic
groups such as protozoan ciliates, including Cyclidium glaucoma, Philodina
erythrophthalma, and Aeolosoma hemprichi, in prey-predator interaction tests,
which were considered to be dominated by these predatory actions. By comparison,
in N 30 , no significant difference was observed between the system with Bacillus
thuringiensis subsp. aizawai KH added and the system without it (control system).
Bacillus thuringiensis subsp. aizawai KH, as a microbial pesticide, showed the
same behavior as Bacillus cereus MC, one of the indigenous bacteria acting as a
control. That is, these foreign bacteria decreased in the microcosm and did not
strongly influence the indigenous microorganisms in the microcosm. As described
in Fig. 7.4, the population density of Bacillus thuringiensis subsp. aizawai KH was
7.8 Â 10
7 CFU/mL in the injected day (16th day) and decreased to 1.1 Â 10
6 CFU/
mL 2 days after (18th day), 2.2 Â 10
4 CFU/mL 7 days after (23rd day), and
9.8 Â 10
3 CFU/mL 14 days after (30th day). In a manner similar to the population
density of Bacillus thuringiensis subsp. aizawai KH, the spores did not increase in
abundance but survived at a fixed density of 5.8 Â 10
2 N/mL after injection into the
microcosm. This was because heterotrophs disliked the Bacillus thuringiensis spores
as a food source, and vegetative cells produced spores without interruption. It was
made clear that the predator-prey interaction between Bacillus thuringiensis and
heterotrophs played a significant role in the proliferation and decay of microbial
pesticides. After the injection of Bacillus thuringiensis and Bacillus cereus, a rapid
increase in the number of protozoa, especially Cyclidium glaucoma, was observed.
This suggested that the predator-prey interaction between foreign bacteria injected,
such as microbial pesticide and protozoa, existed. This suggests that the proliferation
and decay of microbial pesticides were greatly affected by the predation of heterotrophs, especially protozoa, which inhabited the microcosm system.
From an estimation of the succession pattern of microorganisms as the structural
parameter, the protozoa Cyclidium glaucoma was strongly influenced by Bacillus
thuringiensis subsp. aizawai KH, and this protozoa increased in its abundance under
the Bacillus thuringiensis addition, and other microorganisms, such as the rotifers,
Lecane sp. and Philodina erythrophthalma, also increased compared with the
control microcosm. Thus, the influence of Bacillus thuringiensis was different in
different microorganisms in coexisting culture conditions, such as the microcosm
system. The water quality, that is, the pH, rose with the Bacillus thuringiensis
addition, but the value of the pH was approximately 8.5 to 9.5 across all experiments. From an estimation of N 30 using the Bacillus thuringiensis addition, all
species of microorganisms increased in abundance. From an estimation of B 16–30 ,
the same as in N 30 , all microorganisms increased (Fig. 7.34).
Moreover, almost the same behavior was seen from the introduced Bacillus
thuringiensis subsp. aizawai KH as bacterial microbial pesticide was observed in a
7 Example Assessments of the Microcosm N-System
135
has Sm
r and Rf
r as markers. Bacillus thuringiensis subsp. aizawai KH rapidly
decreased at 1, 10, or 100 times inoculation concentrations in viable counts using
the selective media method, following microcosm inoculation, and the abundance of
microorganisms (in particular, its primary consumer, the protozoan ciliate,
Cyclidium glaucoma) in the microcosm increased. Bacillus thuringiensis subsp.
aizawai KH has shown to be a suitable food source for constituent heterotrophic
groups such as protozoan ciliates, including Cyclidium glaucoma, Philodina
erythrophthalma, and Aeolosoma hemprichi, in prey-predator interaction tests,
which were considered to be dominated by these predatory actions. By comparison,
in N 30 , no significant difference was observed between the system with Bacillus
thuringiensis subsp. aizawai KH added and the system without it (control system).
Bacillus thuringiensis subsp. aizawai KH, as a microbial pesticide, showed the
same behavior as Bacillus cereus MC, one of the indigenous bacteria acting as a
control. That is, these foreign bacteria decreased in the microcosm and did not
strongly influence the indigenous microorganisms in the microcosm. As described
in Fig. 7.4, the population density of Bacillus thuringiensis subsp. aizawai KH was
7.8 Â 10
7 CFU/mL in the injected day (16th day) and decreased to 1.1 Â 10
6 CFU/
mL 2 days after (18th day), 2.2 Â 10
4 CFU/mL 7 days after (23rd day), and
9.8 Â 10
3 CFU/mL 14 days after (30th day). In a manner similar to the population
density of Bacillus thuringiensis subsp. aizawai KH, the spores did not increase in
abundance but survived at a fixed density of 5.8 Â 10
2 N/mL after injection into the
microcosm. This was because heterotrophs disliked the Bacillus thuringiensis spores
as a food source, and vegetative cells produced spores without interruption. It was
made clear that the predator-prey interaction between Bacillus thuringiensis and
heterotrophs played a significant role in the proliferation and decay of microbial
pesticides. After the injection of Bacillus thuringiensis and Bacillus cereus, a rapid
increase in the number of protozoa, especially Cyclidium glaucoma, was observed.
This suggested that the predator-prey interaction between foreign bacteria injected,
such as microbial pesticide and protozoa, existed. This suggests that the proliferation
and decay of microbial pesticides were greatly affected by the predation of heterotrophs, especially protozoa, which inhabited the microcosm system.
From an estimation of the succession pattern of microorganisms as the structural
parameter, the protozoa Cyclidium glaucoma was strongly influenced by Bacillus
thuringiensis subsp. aizawai KH, and this protozoa increased in its abundance under
the Bacillus thuringiensis addition, and other microorganisms, such as the rotifers,
Lecane sp. and Philodina erythrophthalma, also increased compared with the
control microcosm. Thus, the influence of Bacillus thuringiensis was different in
different microorganisms in coexisting culture conditions, such as the microcosm
system. The water quality, that is, the pH, rose with the Bacillus thuringiensis
addition, but the value of the pH was approximately 8.5 to 9.5 across all experiments. From an estimation of N 30 using the Bacillus thuringiensis addition, all
species of microorganisms increased in abundance. From an estimation of B 16–30 ,
the same as in N 30 , all microorganisms increased (Fig. 7.34).
Moreover, almost the same behavior was seen from the introduced Bacillus
thuringiensis subsp. aizawai KH as bacterial microbial pesticide was observed in a
7 Example Assessments of the Microcosm N-System
135