Alecia Anirudhe
Pigment in microbes can have multiple functions. For example, it can be used for photosynthesis or for protections against UV light. However, this Janthinobacterium lividum bacterium uses its purple pigment as protection against other microbes. And this is not only useful for bacterium’s own survival, but also for animals working with it, like the red-backed salamander.
Latin name: Janthinobacterium lividum
Size: 2.5-6.0 µm
Lives: in soil and water
Eats: carbohydrates, like glycerol
Enemies: other microbes, like bacteria and fungi
The dark purple appearance of Janthinobacterium lividum is caused by the substance violacein, produced by the bacterium itself. This pigment is an antioxidant, and also has anti-fungal and anti-bacterial effects. For us, violacein, the purple pigment can be useful in the future for its anticancer and antibiotic effect. However, nowadays the pigment is only used for dyeing fibres. Unfortunately, Janthinobacterium lividum can also cause the spoilage of milk.
Violacein has biological properties with possible medical applications, including antibacterial, antiparasitic, antifungal and antitumour activities (Choi et al., 2015; Durán et al., 2012). Since the discovery of violacein, the physiological significance of this pigment has remained unclear. However, Matz et al. (2004) suggested that violacein is involved in chemical defence in bacteria. Violacein also exhibits cytotoxicity to various tumour cell lines through the induction of apoptosis (Alshatwi, Subash-Babu, & Antonisamy, 2016; Bromberg et al., 2010; Ferreira et al., 2004; Kodach et al., 2006). However, the molecular mechanisms and target molecules involved in this toxicity have not been determined.
Violacein-producing bacteria, with their striking purple hues, have undoubtedly piqued the curiosity of scientists since their first discovery. The bisindole violacein is formed by the condensation of two tryptophan molecules through the action of five proteins. The genes required for its production, and the regulatory mechanisms employed have been studied within a small number of violacein-producing strains. As a compound, violacein is known to have diverse biological activities, including being an anticancer agent and being an antibiotic against Staphylococcus aureus and other Gram-positive pathogens. Identifying the biological roles of this pigmented molecule is of particular interest, and understanding violacein's function and mechanism of action has relevance to those unmasking any of its commercial or therapeutic benefits. Unfortunately, the production of violacein and its related derivatives is not easy and so various groups are also seeking to improve the fermentative yields of violacein through genetic engineering and synthetic biology. This review discusses the recent trends in the research and production of violacein by both natural and genetically modified bacterial strains.
1IndBioCat Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
The disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis, is associated with recent declines in amphibian populations. Susceptibility to this disease varies among amphibian populations and species, and resistance appears to be attributable in part to the presence of antifungal microbial species associated with the skin of amphibians. The betaproteobacterium Janthinobacterium lividum has been isolated from the skins of several amphibian species and produces the antifungal metabolite violacein, which inhibits B. dendrobatidis. In this study, we added J. lividum to red-backed salamanders (Plethodon cinereus) to obtain an increased range of violacein concentrations on the skin. Adding J. lividum to the skin of the salamander increased the concentration of violacein on the skin, which was strongly associated with survival after experimental exposure to B. dendrobatidis. As expected from previous work, some individuals that did not receive J. lividum and were exposed to B. dendrobatidis survived. These individuals had concentrations of bacterially produced violacein on their skins that were predicted to kill B. dendrobatidis. Our study suggests that a threshold violacein concentration of about 18 μM on a salamander's skin prevents mortality and morbidity caused by B. dendrobatidis. In addition, we show that over one-half of individuals in nature support antifungal bacteria that produce violacein, which suggests that there is a mutualism between violacein-producing bacteria and P. cinereus and that adding J. lividum is effective for protecting individuals that lack violacein-producing skin bacteria.
The violet pigment violacein is an indole derivative, isolated mainly from bacteria of the genus Chromobacterium, which exhibits important antitumoural, antimicrobial and antiparasitary properties....
We studied the role of bacterial secondary metabolites in the context of grazing protection against protozoans. A model system was used to examine the impact of violacein-producing bacteria on feeding rates, growth, and survival of three common bacterivorous nanoflagellates. Freshwater isolates of Janthinobacterium lividum and Chromobacterium violaceum produced the purple pigment violacein and exhibited acute toxicity to the nanoflagellates tested. High-resolution video microscopy revealed that these bacteria were ingested by the flagellates at high rates. The uptake of less than three bacteria resulted in rapid flagellate cell death after about 20 min and cell lysis within 1 to 2 h. In selectivity experiments with nontoxic Pseudomonas putida MM1, flagellates did not discriminate against pigmented strains. Purified violacein from cell extracts of C. violaceum showed high toxicity to nanoflagellates. In addition, antiprotozoal activity was found to positively correlate with the violacein content of the bacterial strains. Pigment synthesis in C. violaceum is regulated by an N-acylhomoserine lactone (AHL)-dependent quorum-sensing system. An AHL-deficient, nonpigmented mutant provided high flagellate growth rates, while the addition of the natural C. violaceum AHL could restore toxicity. Moreover, it was shown that the presence of violacein-producing bacteria in an otherwise nontoxic bacterial diet considerably inhibited flagellate population growth. Our results suggest that violacein-producing bacteria possess a highly effective survival mechanism which may exemplify the potential of some bacterial secondary metabolites to undermine protozoan grazing pressure and population dynamics.
Disease has spurred declines in global amphibian populations. In particular, the fungal pathogen Batrachochytrium dendrobatidis has decimated amphibian div
Department of Physiological Ecology, Max Planck Institute for Limnology, D-24302 Plön,1 Department of General Ecology and Limnology, Zoological Institute, University of Cologne, D-50923 Cologne,3 Baltic Sea Research Institute Warnemünde, D-18119 Rostock, Germany,5 School of Biotechnology and Biomolecular Sciences, Centre for Marine Biofouling and Bio-Innovation, University of New South Wales, Sydney 2052, New South Wales, Australia,2 Department of Microbiology, Institute of Plant Biology, University of Zürich, CH-8008 Zürich, Switzerland4
