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A Sigma factor gene which is important in the global regulation of heat shock responses in prokaryotes, rpoH, was isolated from Flexibacter chinesis by PCR, sequenced and compared to the rpoH genes of a variety of other organisms. The rpoH gene was 98% similar to other previously characterized genes. A mutant of rpoH was produced (JR102) which had a reduced growth rate at both low and high temperature. JR102 also produced filaments when grown at temperatures greater than the organism’s optimum growth temperature. During the stationary phase when the wild-type cell size was reducing, the cell size of JR102 did not change, suggesting that cells division was inhibited in the mutant. The results presented in this paper suggest that F. chinensis subjected to starvation and other stresses reduces its cell size by miniaturization or cell division to conserve energy. Anything which prevents the formation of these miniaturized cells reduces the chances of the bacterium surviving under stress conditions.