Phage resistance mutation triggered by OmpC deficiency in Klebsiella pneumoniae induced limited fitness costs

Outer membrane proteins (OMPs) play an important role in bacterial fitness costs. Derived from the interaction between Klebsiella pneumoniae K7 and phage GH-K3, K7R(B) is an outer membrane porin-deficient phage-resistant mutant strain triggered by ompC(712) deletion, exhibits expression inhibition of OmpC, OmpN, KPN_02430 and OmpF, but its fitness costs and regulatory mechanism remains unknown. In this study, compared with K7, K7R(B) showed almost unaffected growth rate, slightly decreased virulence, and increased resistance to some antibiotics. Transcriptome analysis showed that the pathways of glycerolipid metabolism and nitrogen metabolism in K7R(B) were significantly inhibited, while the transcription of permeases belonging to ABC transporters tended to be active, nutrient uptakes such as citrate and phenylalanine were also enhanced. However, transcriptional upregulation in K7R(B) was inhibited by overexpression of OmpC, OmpN, KPN_02430 and OmpF in general. Overexpression of OmpN, KPN_02430 and OmpF, respectively, restoring the sensitivity of strains to antibiotics to varying degrees, while OmpC overexpression aggravated the bacterial drug-resistance especially to beta-lactam antibiotics. Besides, unlike OmpC and OmpF, overexpression of OmpN and KPN_02430 reduced bacterial virulence. In brief, by revealing the limited fitness costs of phage-resistant mutant K. pneumoniae with porindeficiency, our study providing a reference for the design and development of drugs to inhibit the ways of bacterial metabolic rewiring and to increase fitness costs.