Identification of plasmids from Brazilian Chromobacterium violaceum strains

Chromobacterium violaceum is an opportunistic pathogen found in tropical and subtropical regions worldwide. Chromobacterium violaceum infections are difficult to treat, and many strains are resistant to antibiotics. Recently, a novel plasmid (pChV1) was discovered in the type strain ATCC 12472, suggesting that other C. violaceum strains may harbor extra-chromosomal DNA. The aim of the present study was to detect and compare new plasmids in Brazilian strains of C. violaceum using next-generation sequencing techniques. We obtained draft genomes of six plasmids from strains isolated from the Amazon region and aligned them with pChV1. At least three plasmids, CVAC05, CVACO2, and CVT8, were similar to pChV1. Phylogenetic analysis suggested that these new extra-chromosomal DNA sequences have a common origin with pChV1 but have diverged. Many of the ORFs detected were related to plasmid segregation/maintenance, viral structural proteins, and proteins with unknown functions. These findings may enable better genetic manipulation of C. violaceum, which will enhance our ability to exploit this valuable microorganism in industrial and clinical applications.

In silico Analysis of Plant Based Quorum Sensing Inhibitor against Chromobacterium violaceum CviR

Background: Chromobacterium violaceum (C. violaceum), a Gram-negative, facultative anaerobic, non-sporing coccobacillus has a quorum-sensing system consisting of CviI/CviR, a homologous gene. Quorum sensing (QS) is a mechanism of intercellular communication in bacteria that received substantial attention as an alternate strategy for combating bacterial resistance and the development of new anti-infective agents. Methods: DATA SET Information of photochemical from the natural source deposited as a machine readable format in PubChem database was utilized to retrieve the compound for the study. To study ligand - receptor interactions, docking paves way to accomplish the protein ligand interaction was docked through rigid docking CviR protein (PDB ID: 3QP5) was prepared and energy minimized to evaluate the best affinity among the complex. Results: The results showed that the Alpha.,2.Alpha.- Epoxy-1.Beta.- Methyl Cholesta-4,6- Dien-3-One had high affinity for CviR receptor protein and Alpha.,2.Alpha.- Epoxy-1.Beta.- Methyl Cholesta-4,6- Dien-3-One binds to the active site of CviR with binding energy of -9.6 kcal/mol. Conclusion: Overall study concluded that 1. Alpha., 2. Alpha.- Epoxy-1.Beta.-Methyl Cholesta-4,6-Dien-3-One with highest binding affinity for the CviR protein possessing strong inhibitory binding interaction. Hence, we concluded that 1.Alpha.,2.Alpha.-Epoxy-1.Beta.- Methyl Cholesta-4, 6-Dien-3-One good serves as potential an anti-quorum sensing molecule for treating C. violaceum infection.

The MarR family regulator OsbR controls oxidative stress response, anaerobic nitrate respiration, and biofilm formation in Chromobacterium violaceum

Background Chromobacterium violaceum is an environmental opportunistic pathogen that causes rare but deadly infections in humans. The transcriptional regulators that C. violaceum uses to sense and respond to environmental cues remain largely unknown. Results Here, we described a novel transcriptional regulator in C. violaceum belonging to the MarR family that we named OsbR (oxidative stress response and biofilm formation regulator). Transcriptome profiling by DNA microarray using strains with deletion or overexpression of osbR showed that OsbR exerts a global regulatory role in C. violaceum, regulating genes involved in oxidative stress response, nitrate reduction, biofilm formation, and several metabolic pathways. EMSA assays showed that OsbR binds to the promoter regions of several OsbR-regulated genes, and the in vitro DNA binding activity was inhibited by oxidants. We demonstrated that the overexpression of osbR caused activation of ohrA even in the presence of the repressor OhrR, which resulted in improved growth under organic hydroperoxide treatment, as seem by growth curve assays. We showed that the proper regulation of the nar genes by OsbR ensures optimal growth of C. violaceum under anaerobic conditions by tuning the reduction of nitrate to nitrite. Finally, the osbR overexpressing strain showed a reduction in biofilm formation, and this phenotype correlated with the OsbR-mediated repression of two gene clusters encoding putative adhesins. Conclusions Together, our data indicated that OsbR is a MarR-type regulator that controls the expression of a large number of genes in C. violaceum, thereby contributing to oxidative stress defense (ohrA/ohrR), anaerobic respiration (narK1K2 and narGHJI), and biofilm formation (putative RTX adhesins).

Chromobacterium violaceum: A Rare Cause of Urinary Tract Infection

A 41-year-old man with a neurogenic bladder due to spinal cord injury (SCI) attended the outpatient department with chief complaints of fever, pain in the lower abdomen, and persistent hematuria for 10 days. From the urine culture and the microbiological and biochemical tests, the causative organism was identified as Chromobacterium violaceum. The isolate was resistant to cephalosporins, while it was sensitive to ofloxacin, gentamicin, and imipenem. Clinicians should be aware of this rare cause of urinary tract infection (UTI), the choice of antibiotic, length of treatment, and necessity of prompt treatment in SCI patients.

Characterization and low-cost preservation of Chromobacterium violaceum strain TRFM-24 isolated from Tripura state, India

Background Chromobacterium species, through their bioactive molecules, help in combating biotic and abiotic stresses in plants and humans. The present study was aimed to identify, characterize and preserve in natural gums the violet-pigmented bacterial isolate TRFM-24 recovered from the rhizosphere soil of rice collected from Tripura state. Results Based on morphological, biochemical and 16S rRNA gene sequencing, the isolate TFRM-24 was identified as Chromobacterium violaceum (NAIMCC-B-02276; MCC 4212). The bacterium is saprophytic, free living and Gram negative. The strain was found positive for production of IAA, cellulase, xylanase and protease, and showed tolerance to salt (2.5%) and drought (-1.2 MPa). However, it showed poor biocontrol activity against soil-borne phytopathogens and nutrient-solubilizing abilitiets. C. violaceum strain TRFM-24 did not survive on tryptic soya agar (TSA) beyond 12 days between 4 and 32 °C temperature hence a method of preservation of this bacterium was attempted using different natural gums namely Acacia nilotica (babul), Anogeissus latifolia (dhavda), Boswellia serrata (salai) and Butea monosperma (palash) under different temperature regime (6–32 °C). The bacterium survived in babul gum (gum acacia), dhavda and salai solution at room temperature beyond a year. Conclusion Based on polyphasic approach, a violet-pigmented isolate TRFM-24 was identified as Chromobacterim violaceum which possessed some attributes of plant and human importance. Further, a simple and low-cost preservation method of strain TRFM-24 at room temperature was developed using natural gums such as babul, dhavda and salai gums which may be the first report to our knowledge.

Assessment of antibacterial potentials of violacein extract from Chromobacterium violaceum isolated from domestic and recreational water sources in Owerri, Nigeria

This study was carried out with the aim of assessing the antibacterial potentials of violacein extracted from Chromobacterium violaceum isolated from domestic and recreational water sources in Owerri, Nigeria. Water samples were collected from different locations of the domestic water sources, five different swimming pools, and three borehole stations using sterile amber bottles. The isolation of C. violaceum was done using pour plate method on nutrient agar. The violet colonies of C. violaceum were counted, characterized and identified using standard microbiological and biochemical techniques. The mean viable bacterial counts were high. Water sample from Otamiri station-1 have the highest bacterial count (200 × 101 CFU/ml and 19.50 × 101 CFU/ml) respectively. Swimming pool 1 and 3 bacterial counts were (4.50 × 101 CFU/ml, 11 × 101 CFU/ml and 11.50 × 101 CFU/ml) respectively. For borehole 1, 2 and 3, swimming pool 2, 4 and 5, counts were (0.00 × 101 CFU/ml). Ethanolic extraction of violacein from C. violaceum was performed from a 48-hour culture broth. The sensitivity of the bacteria isolates to violacein was assayed on nutrient agar and nutrient broth by agar diffusion and broth dilution methods respectively. All the bacterial isolates were susceptible to the violacein extract at various concentrations, except MRSA that showed resistance to the violacein at 2.19mg/ml for extract from recreational water isolate and at 17.5mg/ml to 2.19mg/ml for extract from domestic water isolates. Conclusively, violacein has the potential to be used as an antibacterial compound for treatment of multidrug resistant bacterial infections.