Michelle Zhang

Abstract

Violacein is a natural product (NP), or small molecule found in nature, first isolated from Chromobacterium violaceum in 1991. This purple pigment has become interesting to scientists due to some properties that have promising effects against some diseases in humans, such as malaria and leishmaniasis. In my previous study, the broad-host range vector pCAP05 was used to capture the violacein biosynthetic gene cluster (BGC) transform it into Pseudomonas putida KT2440 (P. putida KT2440), Agrobacterium tumefaciens LBA4213 (A. tumefaciens LBA4213), and Escherichia coli (E. coli). However, violacein production was only observed in P. putida KT2440 and A. tumefaciens LBA4213. Previous work indicates that the violacein BCG is regulated by a quorum sensing mechanism, which is a two-gene system that activates expression based on cell population density. One hypothesis as to why expression was not observed in E. coli is that this system may be present in P. putida KT2440 and A. tumefaciens LBA4213 but is missing or inactive in E. coli hosts. In this study, the well-characterized quorum sensing system from Vibrio fischeri and homologues from P. putida KT2440 and A. tumefaciens LBA4213, were cloned into a co-expression vector. When transformed into E. coli cells with the violacein BGC present, expression of violacein was activated, indicating that the homologues identified and tested contribute to violacein biosynthesis in P. putida KT2440 and A. tumefaciens LBA4213 and may be missing or inactive in E. coli.