Impact of violacein from Chromobacterium violaceum on the mammalian gut microbiome

Abstract

Violacein is a violet pigment produced by Chromobacterium violaceum that possesses several functions such as antibacterial, antiviral, antifungal, and antioxidant activities. The search for potential compounds and therapies that may interfere with and modulate the gut microbial consortia without causing severe damage and increased resistance is important for the treatment of inflammatory, allergic, and metabolic diseases. The aim of the present work was to evaluate the ability of violacein to change microbial patterns in the mammalian gut by favoring certain groups over the others in order to be used as a therapy for diseases associated with changes in the intestinal microflora. To do this, we used male Wistar rats, and administered violacein orally, in low (50 μg/ml) and high (500 μg/ml) doses for a month. Initially, the changes in the microbial diversity were observed by DGGE analyses that showed that the violacein significantly affects the gut microbiota of the rats. Pyrosequencing of 16S rDNA was then employed using a 454 GS Titanium platform, and the results demonstrated that higher taxonomic richness was observed with the low violacein treatment group, followed by the control group and high violacein treatment group. Modulation of the microbiota at the class level was observed in the low violacein dose, where Bacilli and Clostridia (Firmicutes) were found as dominant. For the high violacein dose, Bacilli followed by Clostridia and Actinobacteria were present as the major components. Further analyses are crucial for a better understanding of how violacein affects the gut microbiome and whether this change would be beneficial to the host, providing a framework for the development of alternative treatment strategies for intestinal diseases using this compound.

Modulation of gut microbiota in healthy rats after exposure to nutritional supplements

“…77,84 Also, in the study of Pauer et al, rats received violacein directly in the mouth, twice a day, by gavage for a month. 86 Typically, six to 12 animals are assigned to each group although variations have been seen. Therefore, the smallest number of animals in a group was three, while the largest groups comprised 18 animals.…”

“…37 In the study of Pauer et al whole intestinal content was collected, while Han et al sampled ileal, cecal, and colonic content separately. 66,86 The samples are then stored at −80°C (in some cases −40°C and −20°C) until further analysis.…”

“…For instance, violacein is a natural violet pigment produced by Chromobacterium violaceum with broad antibacterial, antiviral, antifungal, and antioxidant properties, however, its effect on rat gut microbiota of Wistar rats has been explored recently. 86…”

“… 13 weeks DNA extraction (PowerSoil® DNA Isolation kit) next generation sequencing of the PCR amplified V3/V4 region of the 16 S rRNA gene (Illumina MiSeq) QIIME ↑ Bacteroidetes phylum in doses of 111, 223, and 446 mg/kg (mostly due to family Prevotellaceae and S24-7) ↑ Verrucomicrobia phylum in doses of 223 and 446 mg/kg ↓ Firmicutes phylum in doses of 111, 223, and 446 mg/kg(mostly due to family Ruminococcaceae , Lachnispiraceae ) ↓class Clostridia in the 111, 223, and 446 mg/kg 85 Natural pigments Natural pigment violacein from Chromobacterium violaceum 16, 2-month-old, male Wistar albino rats n = 6, 50 μg/mL violacein n = 6, 500 μg/mL violacein n = 4, control group Whole intestinal content collected. One month DNA extraction using QIAamp DNA Stool Minikit and MoBio PowerSoil DNA Isolation kit PCR amplificaton Denaturing Gradient Gel Electrophoresis Pyrosequencing QIIME PICRUSt Higher richness ↑ Firmicutes ↓ Proteobacteria ↑ Lactobacillaceae family Bacilli, Clostridia, Bacteroidia among dominant classes in low violacein group Actinobacteria, Coriobacteria in high violacein group 86 ↑- increased abundance, ↓ -decreased abundance, BW-body weight …”

“… 77 , 84 Also, in the study of Pauer et al ., rats received violacein directly in the mouth, twice a day, by gavage for a month. 86 …”