Doctor of Philosophy (PhD)
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LptD, SurA, PdxA, Outer membrane protein, alginate, CF, Vitamin B6, PLP
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Pseudomonas aeruginosais an opportunistic pathogen that infects cystic fibrosis (CF) patients contributing to their high morbidity and mortality. P. aeruginosaundergoes a phenotypic conversion in the CF lung, from nonmucoid to mucoid, by constitutively producing a polysaccharide called alginate. These mucoid strains often revert to nonmucoid in vitrodue to second-site suppressor mutations. We hypothesized that mapping these mutations would lead to the identification of novel genes involved in alginate production. In a previous study, a mucoid strain, PDO300 (PAOmucA22), was used to isolate suppressors of alginate phenotype (sap). One of the uncharacterized nonmucoid revertants, sap27, is the subject of this study. The mucoid phenotype in sap27was restored by pMO012217 from a minimal tiling path cosmid library. The cosmid pMO012217 harbors 18 P. aeruginosaopen reading frames (ORF). The cosmid was mutagenized with a transposon to map the contributing gene. It was mapped tolptD(PA0595) encoding lipopolysaccharide transport protein. E. coliLptD transports lipopolysaccharide to the outer leaflet of the outer membrane. The Alg+phenotype was restored upon complementation with P. aeruginosa lptDalone, suggesting that sap27likely harbor a chromosomal mutation inlptD. Sequencing analysis of sap27showed the presence of a mutation not in lptDbut in algO, which encodes a periplasmic protease protein. This suggests LptD is able to bypass analgO mutation by positively regulating alginate production. The lptD is a part of a three-gene operon lptD-surA-pdxA. SurA is an essential protein for survival in starvation and a major chaperone protein for all outer membrane proteins and PdxA is a NAD-dependent dehydrogenase and is involved in the vitamin B6biosynthetic pathway. Pyridoxal 5’-phosphate (PLP) is the active form of vitamin B6.P. aeruginosagrown in a media supplemented with PLP increased production of pyocyanin, a virulence factor. The PLP and aromatic amino acids are synthesized from a common precursor chorismic acid. We demonstrated an increase in pyocyanin production when the bacteria were cultured supplemented by the aromatic amino acids phenylalanine. We concluded that the lptDoperon plays a role in the P. aeruginosavirulence by regulating alginate and pyocyanin production.
Pandey, Sundar, "Novel Role of Pseudomonas Aeruginosa LptD Operon" (2018). FIU Electronic Theses and Dissertations. 3734.
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