Recombinant Chromobacterium violaceum 2-nonaprenyl-3-methyl-6-methoxy-1,4-benzoquinol hydroxylase (coq7)

Introduction

Chromobacterium violaceum is a Gram-negative bacterium known for producing violacein, a purple pigment with antimicrobial and antiparasitic properties . This bacterium employs quorum sensing, a mechanism to detect and respond to changes in cell population density, which is crucial for its pathogenicity . C. violaceum's metabolic versatility allows it to survive in diverse environments, making it capable of adapting to various stresses and utilizing different energy production methods under both aerobic and anaerobic conditions .

Quorum Sensing in Chromobacterium violaceum

Quorum sensing in C. violaceum relies on a LuxIR-type system . This system involves the CviI protein, an autoinducer synthase, and the CviR protein, which regulates gene expression in response to autoinducer signals . The interaction between CviR and autoinducers directly regulates the cviI promoter, creating a positive feedback loop that enhances autoinducer production at high cell densities .

CviR Regulation and DNA Binding

The CviR protein binds to specific DNA sequences to regulate gene expression . Studies have identified an ideal CviR binding site, CTGNCCNNNNGGNCAG, which helps predict CviR-regulated genes within the C. violaceum genome . This regulation affects various phenotypes, including biofilm formation and chitinase production, although the directness of this regulation is not fully understood .

Role of ChuPRSTUV System in Heme and Hemoglobin Utilization

The ChuPRSTUV system in C. violaceum is involved in heme and hemoglobin utilization . This system includes genes such as chuP, chuR, chuS, chuT, chuU, and chuV, which are co-transcribed and organized into an operon . The ChuP regulator, a HemP/HmuP family protein, plays a key role in this system, which also involves a TonB-dependent receptor (ChuR), a hemin-degrading factor (ChuS), and an ABC-transport system (ChuTUV) .

Importance of Heme Uptake During Infection

Heme uptake is crucial for the virulence of C. violaceum, particularly in the absence of siderophores . While the absence of both siderophores and heme uptake does not impair initial colonization, it affects bacterial maintenance during later stages of infection . This interplay between iron-acquisition strategies highlights the importance of heme uptake for bacterial survival within the host .

Violacein Production and Regulation

C. violaceum produces violacein, a pigment with antimicrobial properties . Violacein synthesis occurs under aerobic conditions and is influenced by environmental signals . For example, hygromycin A from Streptomyces sp. induces violacein production in C. violaceum ATCC 31532 . Antibiotics like tetracycline and spectinomycin also affect gene expression related to violacein production, indicating a complex regulatory network .