Determination of Microbial Production
189
Fig. 4.8. Stand for postfiltration procedure through
Nucleopore filter without external vacuum
eutrophic and mesotrophic waters 120-200-ml bottles can be used, while in
poor waters their volume should be greater: 2S0-300m!. Such bottles are used
if each of two parallel subsamples are filtered separately; but it is more convenient and more accurate from the point of possible bottle effects to make
two parallel filtrations from a double volume of the same sample. I have known
colleagues who have unhesitatingly used even 30-ml penicillin bottles for this
purpose, which was completely wrong, because it is impossible to keep the
ambient redox potential in such small bottles with a large relative surface. The
bottles are sterilized with Lugol solution and prepared for work as described
above (see Sect. 2.3.2.3). For their sterilization neither autoclave nor dry sterilization can be used.
The working solution of 14C-carbonate must be prepared by passing the
batch of concentrated isotope via the gas phase for cleaning. Then it must be
treated exactly as described above (see Sect. 2.3.2.1), with its radioactivity
adjusted to about one order more for the accurate measuring of 14C02 uptake
in experiments of given duration: 1 ml working solution for dark 14C02 uptake
measurement should have a radioactivity of 60-100 x 10 6 cpm (30-S0f.lCi). In
this case, 0.20-0.30ml may be injected into the experimental bottles, its portions depending upon the productivity of the basin and the volume of bottles
in use. This ready working solution, having a pH of -9.0-9.2, is filtered twice
through Sartorius membrane filters with 0.10-0.lS-f.lm pores. Then the solution is distributed into 2-ml glass ampules, which are sealed and sterilized. The
189
Fig. 4.8. Stand for postfiltration procedure through
Nucleopore filter without external vacuum
eutrophic and mesotrophic waters 120-200-ml bottles can be used, while in
poor waters their volume should be greater: 2S0-300m!. Such bottles are used
if each of two parallel subsamples are filtered separately; but it is more convenient and more accurate from the point of possible bottle effects to make
two parallel filtrations from a double volume of the same sample. I have known
colleagues who have unhesitatingly used even 30-ml penicillin bottles for this
purpose, which was completely wrong, because it is impossible to keep the
ambient redox potential in such small bottles with a large relative surface. The
bottles are sterilized with Lugol solution and prepared for work as described
above (see Sect. 2.3.2.3). For their sterilization neither autoclave nor dry sterilization can be used.
The working solution of 14C-carbonate must be prepared by passing the
batch of concentrated isotope via the gas phase for cleaning. Then it must be
treated exactly as described above (see Sect. 2.3.2.1), with its radioactivity
adjusted to about one order more for the accurate measuring of 14C02 uptake
in experiments of given duration: 1 ml working solution for dark 14C02 uptake
measurement should have a radioactivity of 60-100 x 10 6 cpm (30-S0f.lCi). In
this case, 0.20-0.30ml may be injected into the experimental bottles, its portions depending upon the productivity of the basin and the volume of bottles
in use. This ready working solution, having a pH of -9.0-9.2, is filtered twice
through Sartorius membrane filters with 0.10-0.lS-f.lm pores. Then the solution is distributed into 2-ml glass ampules, which are sealed and sterilized. The