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Growth Response of Bradyrhizobium japonicum RCR3407 to Heat Hardening Treatments.

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Author(s): Mohammad Ibrahim Keerio | Mohammad Ashraf Mirjat | Shanila Yasmeen Chang | Irfana Parveen Bhatti

Journal: Journal of Biological Sciences
ISSN 1727-3048

Volume: 1;
Issue: 9;
Start page: 877;
Date: 2001;
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Keywords: B. rhizobium japonicum | heat-hardening | temperature | optical density | pH

ABSTRACT
Heat-hardening treatments indicates that B.rhizobium japonicum can grow better at high temperatures. During first 12h of incubation (after hardening at 40�C) the rhizobia sometimes grew less well than the controls, but growth then increased more quickly up to 36h of incubation compared to controls. A small decrease in cell population was measured after 48h, however, similar to that in the control. At 45�C, the heat-hardened rhizobia grew similar to the controls during the first 12h, then a sharp increase was found after 36h. Growth was then much better in the hardened cultures than controls. Same time at 40�C, the pH declined sharply after 12h and remained stable on further incubation. However, the pH of the culture which was incubated at 45�C did not decline during the first 24h of incubation and only a very slow decline was found after that. Similar results were found in the cultures which had been hardened at 45�C. In cultures which were incubated at 40�C, the pH decreased slightly after 12h of incubation and became stable on further incubation. At 45�C, decrease in the pH was not found up to 24h and then a small decline take place with increasing incubation periods.
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