Outer membrane (OM) is a crucial layer of defence for Gram-negative bacteria. Within the OM lies plethora of proteins and among those, porins are essential components that allow passage of solutes into the cells. The OmpK35 and OmpK36 are known as the major porins of Klebsiella species, and their mutations are highly relevant to antimicrobial resistance. Interestingly, there are two quiescent porins which are structurally similar to them, namely OmpK37 and OmpK38. While the redundancy is puzzling, they are deemed as quiescent porins since discovery because they are not expressed under standard laboratory conditions. The histone-like nucleoid-structuring protein (H-NS) plays an important role of gene repressions in Gram-negative bacteria. Multiple H-NS form a nucleofilament upstream of their target and bridge the adjacent DNA which is subject to environmental cues that would influence the conformation of H-NS. Currently, we have found that excessive LeuO, an H-NS antagonist, upregulates both OmpK37 and OmpK38, determined by RT-qPCR and Western blot. Furthermore, OmpK37 but not OmpK38 was upregulated in the loss of hns, supporting the notion that H-NS regulates the porins but does not explain the regulation of ompK38. It is likely that ompK38 is a transcriptional target of LeuO which is not repressed by H-NS since LeuO is known to target genes free of H-NS as well. Prokaryotes have developed such convoluted way to keep a subset of genes repressed but expressed under unique conditions. Hence, the conditions and mechanisms of their expressions constitute invaluable information regarding response towards antimicrobials in Gram-negative bacteria.