was faster under higher-temperature culture conditions. Namely, growth was delayed,
the peak abundance of Cyclidium glaucoma appeared 20 days after cultivation began,
and a high population density was maintained at 10
C. However, the population sizes
of other microanimals were lower than 10 N/mL, and the dominant species of bacteria
was represented by only three individuals. At 20
C, the peak abundances of bacteria
and Cyclidium glaucoma appeared 7 days after cultivation began, and the population
of Cyclidium glaucoma stabilized at ~150 N/mL. Other microorganisms also had more
than 1 N/mL after 21 days, but the dominant species of bacteria was represented by
only one individual. At 25
C, all microorganisms exhibited concentrations of more
than 1 N/mL by the 7th day, and a steady state was maintained after the 14th day. In
the steady state, microanimals coexisted as ~100 N/mL of Cyclidium glaucoma, 30 N/
mL of Lecane sp., 40 N/mL of Philodina erythrophthalma, and 10 N/mL of
Aeolosoma hemprichi. At 30
C, the succession pattern was fairly similar to that at
25
C, but a decrease in the abundance of Cyclidium glaucoma by the 7th day was
conspicuous. The microcosm culture allowing for high stability and serial transferring
on a monthly cycle was determined to be 25
C.
2.1.5 Illuminance
Material circulation in ecosystems begins with photosynthesis by plants and
microalgae, such as chlorophytes and blue-green algae, which filled this niche in
the experimental microcosm. To establish a standard condition for illuminance, the
light/dark (L/D) cycle was investigated. An L/D cycle, with 12 hr each, was
considered appropriate because the succession of microbiota was smooth. Even
under a 16 hr/8 hr cycle of light/dark illuminance, the microcosm reached a steady
state; however, the lifespan of the fluorescent lamp was short. Under both 24 hr/0 hr
(total light) and 0 hr/24 hr (total darkness) conditions of illuminance, the succession
of microbiota was unstable.
2.1.6 Substrate Concentration
While the medium is important for cultivating the microcosm, the substrate concentration is of greater importance. To obtain a stable microcosm, the effect of the
substrate concentration was investigated; 25 mg/L, 50 mg/L, and 100 mg/L of
polypeptone were added to Taub’s basal medium, and the microcosm was cultured
under these conditions. The microcosm was able to reach a steady state under all of
these conditions, but there was an observed tendency toward population decline and
extinction of some species of microorganisms under the 25 mg/L of polypeptone
condition. From the results obtained in these experiments, it was determined that a
100 mg/L concentration of polypeptone was safe.
14
K. Murakami et al.
the peak abundance of Cyclidium glaucoma appeared 20 days after cultivation began,
and a high population density was maintained at 10
C. However, the population sizes
of other microanimals were lower than 10 N/mL, and the dominant species of bacteria
was represented by only three individuals. At 20
C, the peak abundances of bacteria
and Cyclidium glaucoma appeared 7 days after cultivation began, and the population
of Cyclidium glaucoma stabilized at ~150 N/mL. Other microorganisms also had more
than 1 N/mL after 21 days, but the dominant species of bacteria was represented by
only one individual. At 25
C, all microorganisms exhibited concentrations of more
than 1 N/mL by the 7th day, and a steady state was maintained after the 14th day. In
the steady state, microanimals coexisted as ~100 N/mL of Cyclidium glaucoma, 30 N/
mL of Lecane sp., 40 N/mL of Philodina erythrophthalma, and 10 N/mL of
Aeolosoma hemprichi. At 30
C, the succession pattern was fairly similar to that at
25
C, but a decrease in the abundance of Cyclidium glaucoma by the 7th day was
conspicuous. The microcosm culture allowing for high stability and serial transferring
on a monthly cycle was determined to be 25
C.
2.1.5 Illuminance
Material circulation in ecosystems begins with photosynthesis by plants and
microalgae, such as chlorophytes and blue-green algae, which filled this niche in
the experimental microcosm. To establish a standard condition for illuminance, the
light/dark (L/D) cycle was investigated. An L/D cycle, with 12 hr each, was
considered appropriate because the succession of microbiota was smooth. Even
under a 16 hr/8 hr cycle of light/dark illuminance, the microcosm reached a steady
state; however, the lifespan of the fluorescent lamp was short. Under both 24 hr/0 hr
(total light) and 0 hr/24 hr (total darkness) conditions of illuminance, the succession
of microbiota was unstable.
2.1.6 Substrate Concentration
While the medium is important for cultivating the microcosm, the substrate concentration is of greater importance. To obtain a stable microcosm, the effect of the
substrate concentration was investigated; 25 mg/L, 50 mg/L, and 100 mg/L of
polypeptone were added to Taub’s basal medium, and the microcosm was cultured
under these conditions. The microcosm was able to reach a steady state under all of
these conditions, but there was an observed tendency toward population decline and
extinction of some species of microorganisms under the 25 mg/L of polypeptone
condition. From the results obtained in these experiments, it was determined that a
100 mg/L concentration of polypeptone was safe.
14
K. Murakami et al.