Comparison of gene expression among normally divided cells, elongated cells, spheroplasts at the beginning of growth, and enlarged spheroplasts at 43 h of growth in Lelliottia amnigena

Abstract

We compared the expression levels of cell division related genes ftsA and ftsZ, DNA maintenance related genes hupA, recA, and topA, stress response related genes clpB, pspA and spy, and outer membrane synthesis related genes ompA and pbp1b, among normally divided cells, elongated (filamentous) cells, spheroplasts at the beginning of growth, and enlarged spheroplasts at 43h of growth in Lelliottia amnigena, by using quantitative RT-PCR. Although the expression level of ftsA was similar among the four samples, the expression level of ftsZ was higher in spheroplasts, and that in enlarged spheroplasts was the highest among the four samples. Although the hupA and recA expression levels in spheroplasts at 0h and 43h of growth were higher than those in divided cells, their topA expression was lower. This suggests that HupA and RecA may play a role in DNA replication during spheroplast enlargement. The stress response genes clpB, pspA, and spy were upregulated in spheroplasts. However, the expression levels of pspA and spy in enlarged spheroplasts at 43h of growth were lower than those in spheroplasts at the beginning of growth, suggesting that enlarged spheroplasts at 43h may be adapted to stress. The expression level of ompA in spheroplasts at 0h of growth was approximately 3 times higher than that in divided cells, but the ompA expression in spheroplasts at 43h of growth was approximately half of that in divided cells. This suggests that OmpA may be dispensable for spheroplast enlargement. Our findings thus show that the gene expression in spheroplast enlargement is quite different from cell elongation.