Draft Genome Sequence of Violacein-Producing Marine Bacterium Pseudoalteromonas sp. 520P1

Molecular Relationships in Biofilm Formation and the Biosynthesis of Exoproducts in Pseudoalteromonas spp

Most members of the Pseudoalteromonas genus have been isolated from living surfaces as members of epiphytic and epizooic microbiomes on marine macroorganisms. Commonly Pseudoalteromonas isolates are reported as a source of bioactive exoproducts, i.e., secondary metabolites, such as exopolymeric substances and extracellular enzymes. The experimental conditions for the production of these agents are commonly associated with sessile metabolic states such as biofilms or liquid cultures in the stationary growth phase. Despite this, the molecular mechanisms that connect biofilm formation and the biosynthesis of exoproducts in Pseudoalteromonas isolates have rarely been mentioned in the literature. This review compiles empirical evidence about exoproduct biosynthesis conditions and molecular mechanisms that regulate sessile metabolic states in Pseudoalteromonas species, to provide a comprehensive perspective on the regulatory convergences that generate the recurrent coexistence of both phenomena in this bacterial genus. This synthesis aims to provide perspectives on the extent of this phenomenon for the optimization of bioprospection studies and biotechnology processes based on these bacteria.

Multi-target drug with potential applications: violacein in the spotlight

The aim of the current review is to address updated research on a natural pigment called violacein, with emphasis on its production, biological activity and applications. New information about violacein's action mechanisms as antitumor agent and about its synergistic action in drug delivery systems has brought new alternatives for anticancer therapy. Thus, violacein is introduced as reliable drug capable of overcoming at least three cancer hallmarks, namely: proliferative signaling, cell death resistance and metastasis. In addition, antimicrobial effects on several microorganisms affecting humans and other animals turn violacein into an attractive drug to combat resistant pathogens. Emphasis is given to effects of violacein combined with different agents, such as antibiotics, anticancer agents and nanoparticles. Although violacein is well-known for many decades, it remains an attractive compound. Thus, research groups have been making continuous effort to help improving its production in recent years, which can surely enable its pharmaceutical and chemical application as multi-task compound, even in the cosmetics and food industries.

Microbial synthesis of violacein pigment and its potential applications

Violacein is a pigment synthesized by Gram-negative bacteria such as Chromobacterium violaceum. It has garnered significant interest owing to its unique physiological and biological activities along with its synergistic effects with various antibiotics. In addition to C. violaceum, several microorganisms, including: Duganella sp., Pseudoalteromonas sp., Iodobacter sp., and Massilia sp., are known to produce violacein. Along with the identification of violacein-producing strains, the genetic regulation, quorum sensing mechanism, and sequence of the vio-operon involved in the biosynthesis of violacein have been elucidated. From an engineering perspective, the heterologous production of violacein using the genetically engineered Escherichia coli or Citrobacter freundii host has also been attempted. Genetic engineering of host cells involves the heterologous expression of genes involved in the vio operon and the optimization of metabolic pathways and gene regulation. Further, the crystallography of VioD and VioE was revealed, and mass production by enzyme engineering has been accelerated. In this review, we highlight the biologically assisted end-use applications of violacein (such as functional fabric development, nanoparticles, functional polymer composites, and sunscreen ingredients) and violacein activation mechanisms, production strains, and the results of mass production with engineered methods. The prospects for violacein research and engineering applications have also been discussed.

An Overview on Industrial and Medical Applications of Bio-Pigments Synthesized by Marine Bacteria

Marine bacterial species contribute to a significant part of the oceanic population, which substantially produces biologically effectual moieties having various medical and industrial applications. The use of marine-derived bacterial pigments displays a snowballing effect in recent times, being natural, environmentally safe, and health beneficial compounds. Although isolating marine bacteria is a strenuous task, these are still a compelling subject for researchers, due to their promising avenues for numerous applications. Marine-derived bacterial pigments serve as valuable products in the food, pharmaceutical, textile, and cosmetic industries due to their beneficial attributes, including anticancer, antimicrobial, antioxidant, and cytotoxic activities. Biodegradability and higher environmental compatibility further strengthen the use of marine bio-pigments over artificially acquired colored molecules. Besides that, hazardous effects associated with the consumption of synthetic colors further substantiated the use of marine dyes as color additives in industries as well. This review sheds light on marine bacterial sources of pigmented compounds along with their industrial applicability and therapeutic insights based on the data available in the literature. It also encompasses the need for introducing bacterial bio-pigments in global pigment industry, highlighting their future potential, aiming to contribute to the worldwide economy.

The art of adapting to extreme environments: The model system Pseudoalteromonas

Extremophilic microbes have adapted to thrive in ecological niches characterized by harsh chemical/physical conditions such as, for example, very low/high temperature. Living organisms inhabiting these environments have developed peculiar mechanisms to cope with extreme conditions, in such a way that they mark the chemical-physical boundaries of life on Earth. Studying such mechanisms is stimulating from a basic research viewpoint and because of biotechnological applications. Pseudoalteromonas species are a group of marine gamma-proteobacteria frequently isolated from a range of extreme environments, including cold habitats and deep-sea sediments. Since deep-sea floors constitute almost 60% of the Earth's surface and cold temperatures represent the most common of the extreme conditions, the genus Pseudoalteromonas can be considered one of the most important model systems for studying microbial adaptation. Particularly, among all Pseudoalteromonas representatives, P. haloplanktis TAC125 has recently gained a central role. This bacterium was isolated from seawater sampled along the Antarctic ice-shell and is considered one of the model organisms of cold-adapted bacteria. It is capable of thriving in a wide temperature range and it has been suggested as an alternative host for the soluble overproduction of heterologous proteins, given its ability to rapidly multiply at low temperatures. In this review, we will present an overview of the recent advances in the characterization of Pseudoalteromonas strains and, more importantly, in the understanding of their evolutionary and chemical-physical strategies to face such a broad array of extreme conditions. A particular attention will be given to systems-biology approaches in the study of the above-mentioned topics, as genome-scale datasets (e.g. genomics, proteomics, phenomics) are beginning to expand for this group of organisms. In this context, a specific section dedicated to P. haloplanktis TAC125 will be presented to address the recent efforts in the elucidation of the metabolic rewiring of the organisms in its natural environment (Antarctica).

Characterization of LuxI and LuxR Protein Homologs of N-Acylhomoserine Lactone-Dependent Quorum Sensing System in Pseudoalteromonas sp. 520P1

Pseudoalteromonas sp. 520P1 (hereafter referred to as strain 520P1) produces N-acylhomoserine lactones (AHLs), which serve as signaling molecules in Gram-negative bacterial quorum sensing. In a previous genomic analysis of the 5.25-Mb genome of strain 520P1, we detected the presence of at least one homolog of the AHL synthase gene (luxI) and five homologs of the transcriptional regulator protein gene (luxR). The LuxI homolog of strain 520P1 (PalI) contained the conserved amino acid motifs shared by all the LuxI family proteins of the different species examined here. The palI gene expressed in Escherichia coli produced two types of AHLs. In the thin-layer chromatography analysis, these AHLs showed identical mobility to the AHLs produced by strain 520P1. The five LuxR homologs of strain 520P1 (PalR1-PalR5) shared only 17-34% amino acid sequence identity, although higher identities were observed in the C-terminal DNA-binding domain. Among the five PalRs, only PalR5 displayed close homology with LuxR family proteins from other Pseudoalteromonas strains. Notably, the palR3 and palI genes were located close together and only 1021 bases apart in the genome. No cognate luxI homolog associated with the four other palR genes was detected. These characteristics of PalI and the PalRs suggest that AHL autoinducers generated by the PalI enzyme might regulate cellular metabolism in cooperation with five transcriptional regulator PalRs, each of which is presumed to play a distinctive role in bacterial signaling.

Advances in Chromobacterium violaceum and properties of violacein-Its main secondary metabolite: A review

Chromobacterium violaceum is important in the production of violacein, like other bacteria, such as Alteromonas, Janthinobacterium, Pseudoalteromonas, Duganella, Collimonas and Escherichia. Violacein is a versatile pigment, where it exhibits several biological activities, and every year, it shows increasing commercially interesting uses, especially for industrial applications in cosmetics, medicines and fabrics. This review on violacein focuses mainly on the last five years of research regarding this target compound and describes production and importance of quorum sensing in C. violaceum, mechanistic aspects of its biosynthesis, monitoring processes, genetic perspectives, pathogenic effects, antiparasitic and antimicrobial activities, immunomodulatory potential and uses, antitumor potential and industrial applications.