Escherichia coli cells (ATCC-9637) grew well in the artificial sea water (ASW) containing yeast extract (1%), but the cell growth was repressed with increasing concentration of ASW; complete inhibition was observed in 2.5-fold strength ASW (×2.5 ASW). However, if the cells had been previously incubated with the normal concentration of ASW for a short time (30min), they exhibited salt-tolerance and grew well even in the high salinity medium (×2.5 ASW). This induction of salt-tolerance was dependent on both the concentration of ASW and the suitable organic solutes such as yeast extract. The salt-tolerance was maintained for up to 2 weeks when cell were suspended in ASW, but not in distilled water. NaCl as an osmolyte, and Mg²⁺/Ca²⁺ were suggested to be important for the maintenance of the salt-tolerance.

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Experiments were conducted to examine the effect of continuous application of different kinds of straw on methane emission and production in flooded rice soil microcosms. Consecutive cultivation for four years revealed that there was no significant difference in the amounts of methane emitted by plots applied with rice straw and those applied with wheat straw, though emissions varied remarkably from year to year. Methane emission from plots with an application of 6t ha^-1 rice straw or wheat straw increased 3.5 times or 3.4 times compared to that from plots without straw, respectively. Continuous application of straw altered the methanogenic characteristics by increasing the response to glucose added to the soil. The production potential of methane and carbon dioxide was measured by laboratory incubation, and was significantly increased in samples taken from plots receiving straw applications when glucose was added, while there was no response to glucose addition in soil from plots without straw application. In contrast, dissolved carbon including organic acids were accumulated in the control plot. These results indicated that the methane production potential in response to glucose was maintained by continuous application of straws.

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The significance of several factors (pre-culture conditions, competition, and predation) affecting the population dynamics of γ-HCH-decomposing bacterium, Sphingomonas paucimobilis SS86 inoculated to soil was examined. The exponentially-growing cells of SS86 inoculated to soil declined quickly immediately after inoculation. This might be caused by physiological inadaptation of the bacterial cells to the oligotrophic soil environment. Cell of the SS86 pre-cultured and harvested at late-stationary phase showed better survival than growing cells. Competition between the inoculated SS86 and indigenous soil microorganisms for the natural substrate restricted the multiplication of SS86 in γ-HCH-free soil, but its effect on the decline was relatively small. The predominant factor causing the decline of SS86 in soil was considered to be the grazing activity of protozoa.

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The present article reports on the possible genetic transformability of acid tolerance trait to its homologous sensitive counterpart. The plasmid-cured derivative of the acid tolerant bradyrhizobial isolate RJL2 showed significant growth responses in acidified (pH4.5) culture medium, thus showing non-plasmid control of this trait. Acid-sensitive, but rifampicin-resistant (100μg/ml) Bradyrhizobium TAL216 when was exposed to transforming DNA from RJL2 produced transformant cells at a significant frequency showing both acid tolerance and rif-resistance phenotypes. The growth and survival of both acid tolerant strains RJL2 and the resultant transformants were found to be comparable in acidic soil and in culture medium.

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