Role of methionine in biosynthesis of prodigiosin by Serratia marcescens

High-level production of microbial prodigiosin: A review

Prodigiosin is a natural red pigment derived primarily from secondary metabolites of microorganisms, especially Serratia marcescens. It can also be chemically synthesized. Prodigiosin has been proven to have antitumor, antibacterial, antimalaria, anti-insect, antialgae, and immunosuppressive activities, and is gaining increasing important in the global market because of its great potential application value in clinical medicine development, environmental treatment, preparation of food additives, and so on. Due to the low efficiency of prodigiosin chemical synthesis, high-level prodigiosin of production by microorganisms are necessary for prodigiosin applications. In this paper, the production of prodigiosin by microorganism in recent decades is reviewed. The methods and strategies for increasing the yield of prodigiosin are discussed from the aspects of medium composition, additives, factors affecting production conditions, strain modification, and fermentation methods.

Biotechnological Activities and Applications of Bacterial Pigments Violacein and Prodigiosin

In this review, we discuss violacein and prodigiosin, two chromogenic bacterial secondary metabolites that have diverse biological activities. Although both compounds were "discovered" more than seven decades ago, interest into their biological applications has grown in the last two decades, particularly driven by their antimicrobial and anticancer properties. These topics will be discussed in the first half of this review. The latter half delves into the current efforts of groups to produce these two compounds. This includes in both their native bacterial hosts and heterogeneously in other bacterial hosts, including discussing some of the caveats related to the yields reported in the literature, and some of the synthetic biology techniques employed in this pursuit.

LysR-Type Transcriptional Regulator MetR Controls Prodigiosin Production, Methionine Biosynthesis, Cell Motility, H2O2 Tolerance, Heat Tolerance, and Exopolysaccharide Synthesis in Serratia marcescens

Prodigiosin, a secondary metabolite produced by Serratia marcescens, has attracted attention due to its immunosuppressive, antimicrobial, and anticancer properties. However, information on the regulatory mechanism behind prodigiosin biosynthesis in S. marcescens remains limited. In this work, a prodigiosin-hyperproducing strain with the BVG90_22495 gene disrupted (ZK66) was selected from a collection of Tn5G transposon insertion mutants. Using real-time quantitative PCR (RT-qPCR) analysis, β-galactosidase assays, transcriptomics analysis, and electrophoretic mobility shift assays (EMSAs), the LysR-type regulator MetR encoded by the BVG90_22495 gene was found to affect prodigiosin synthesis, and this correlated with MetR directly binding to the promoter region of the prodigiosin-synthesis positive regulator PigP and hence negatively regulated the expression of the prodigiosin-associated pig operon. More analyses revealed that MetR regulated some other important cellular processes, including methionine biosynthesis, cell motility, H₂O₂ tolerance, heat tolerance, exopolysaccharide synthesis, and biofilm formation in S. marcescens Although MetR protein is highly conserved in many bacteria, we report here on the LysR-type regulator MetR exhibiting novel roles in negatively regulating prodigiosin synthesis and positively regulating heat tolerance, exopolysaccharide synthesis, and biofilm formation.IMPORTANCE Serratia marcescens, a Gram-negative bacterium, is found in a wide range of ecological niches and can produce several secondary metabolites, including prodigiosin, althiomycin, and serratamolide. Among them, prodigiosin shows diverse functions as an immunosuppressant, antimicrobial, and anticancer agent. However, the regulatory mechanisms behind prodigiosin synthesis in S. marcescens are not completely understood. Here, we adapted a transposon mutant library to identify the genes related to prodigiosin synthesis, and the BVG90_22495 gene encoding the LysR-type regulator MetR was found to negatively regulate prodigiosin synthesis. The molecular mechanism of the metR mutant hyperproducing prodigiosin was investigated. Additionally, we provided evidence supporting new roles for MetR in regulating methionine biosynthesis, cell motility, heat tolerance, H₂O₂ tolerance, and exopolysaccharide synthesis in S. marcescens Collectively, this work provides novel insight into regulatory mechanisms of prodigiosin synthesis and uncovers novel roles for the highly conserved MetR protein in regulating prodigiosin synthesis, heat tolerance, exopolysaccharide (EPS) synthesis, and biofilm formation.

Enhanced production of prodigiosin by Serratia marcescens MO-1 using ram horn peptone

This work addresses the production of prodigiosin from ram horn peptone (RHP) using MO-1, a local isolate in submerged culture. First, a novel gram-negative and rod-shaped bacterial strain, MO-1, was isolated from the body of the grasshopper (Poecilemon tauricola Ramme 1951), which was collected from pesticide-contaminated fields. Sequence analysis of 16S rDNA classified the microbe as Serratia marcescens. The substrate utilization potential (BIOLOG) and fatty acid methyl ester profile (FAME) of S. marcescens were also determined. The effect of RHP on the production of prodigiosin by S. marcescens MO-1 was investigated, and the results showed that RHP supplementation promoted the growth of MO-1 and increased the production of prodigiosin. A concentration of 0.4% (w/v) RHP resulted in the greatest yield of prodigiosin (277.74 mg/L) after 48 h when mannitol was used as the sole source of carbon. The pigment yield was also influenced by the types of carbon sources and peptones. As a result, RHP was demonstrated to be a suitable substrate for prodigiosin production. These results revealed that prodigiosin could be produced efficiently by S. marcescens using RHP.

Viscosity dictates metabolic activity of Vibrio ruber

Little is known about metabolic activity of bacteria, when viscosity of their environment changes. In this work, bacterial metabolic activity in media with viscosity ranging from 0.8 to 29.4 mPas was studied. Viscosities up to 2.4 mPas did not affect metabolic activity of Vibrio ruber. On the other hand, at 29.4 mPas respiration rate and total dehydrogenase activity increased 8 and 4-fold, respectively. The activity of glucose-6-phosphate dehydrogenase (GPD) increased up to 13-fold at higher viscosities. However, intensified metabolic activity did not result in faster growth rate. Increased viscosity delayed the onset as well as the duration of biosynthesis of prodigiosin. As an adaptation to viscous environment V. ruber increased metabolic flux through the pentose phosphate pathway and reduced synthesis of a secondary metabolite. In addition, V. ruber was able to modify the viscosity of its environment.

Development of natural anti-tumor drugs by microorganisms

Discoveries of tumor-resistant pharmacological drugs have mainly resulted from screening of natural products and their analogs. Some are also discovered incidentally when studying organisms. The great biodiversity of microorganisms raises the possibility of producing secondary metabolites (e.g., mevastatin, lovastatin, epothilone, salinosporamide A) to cope with adverse environments. Recently, natural plant pigments with anti-tumor activities such as β-carotene, lycopene, curcumin and anthocyanins have been proposed. However, many plants have a long life cycle. Therefore, pigments from microorganisms represent another option for the development of novel anti-tumor drugs. Prodigiosin (PG) is a natural red pigment produced by microorganisms, i.e., Serratia marcescens and other gram-negative bacteria. The anti-tumor potential of PG has been widely demonstrated. The families of PG (PGs), which share a common pyrrolylpyrromethene (PPM) skeleton, are produced by various bacteria. PGs are bioactive pigments and are known to exert immunosuppressive properties, in vitro apoptotic effects, and in vivo anti-tumor activities. Currently the most common strain used for producing PGs is S. marcescens. However, few reports have discussed PGs production. This review therefore describes the development of an anti-tumor drug, PG, that can be naturally produced by microorganisms, and evaluates the microbial production system, fermentation strategies, purification and identification processes. The application potential of PGs is also discussed.

The biosynthesis and regulation of bacterial prodiginines

The red-pigmented prodiginines are bioactive secondary metabolites produced by both Gram-negative and Gram-positive bacteria. Recently, these tripyrrole molecules have received renewed attention owing to reported immunosuppressive and anticancer properties. The enzymes involved in the biosynthetic pathways for the production of two of these molecules, prodigiosin and undecylprodigiosin, are now known. However, the biochemistry of some of the reactions is still poorly understood. The physiology and regulation of prodiginine production in Serratia and Streptomyces are now well understood, although the biological role of these pigments in the producer organisms remains unclear. However, research into the biology of pigment production will stimulate interest in the bioengineering of strains to synthesize useful prodiginine derivatives.

Enhanced undecylprodigiosin production from Serratia marcescens SS-1 by medium formulation and amino-acid supplementation

Serratia marcescens Simon Swift-1 (SS-1) was used to produce a prodigiosin-like pigment, undecylprodigiosin (UP), known to have antitumor activities and potential as an anticancer drug. Modified media containing components of Luria-Bertani (LB) broth and selected amino acids were used to improve UP production from S. marcescens SS-1. Optimal culture conditions (e.g., temperature, pH, agitation rate) for UP production were also identified. It was found that S. marcescens SS-1 was able to produce 690 mg l-1 of UP when it was grown with 5 g l-1 yeast extract alone (YE medium) under the optimal culture conditions of 30 degrees C, 200 rpm, and pH 8. The UP production of 690 mg l-1 is nearly 23-fold of that obtained from original LB medium. Addition of amino acids containing pyrrole-like structures further enhanced UP production. Nearly 2 and 1.4 g l-1 of UP was produced when the SS-1 strain was cultivated with YE medium supplemented with proline and histidine (5 g l-1), respectively. Moreover, the addition of aspartic acid (5 g l-1) also resulted in a high UP production of 1.4 g l-1. Optimal dosages of the three amino acids were subsequently determined and the highest UP production (2.5 g l-1) was achieved with the addition of 10 g l-1 of proline. This suggests that the supplementation of amino acids related to the formation of a UP precursor (e.g., pyrrolylpyrromethene) could enhance UP production by the SS-1 strain.

Lipopolysaccharide is the receptor for kappa phage in Serratia marcescens

Kappa phage active on Serratia marcescens can form plaques on white and red strains with identical efficiencies. To identify the kappa phage receptor, the inactivation of the phage was studied after incubation with several bacterial subcellular fractions. The experiments demonstrated that kappa phage adsorbs to outer membrane fractions of susceptible cells. Proteinase K did not affect the rate of inactivation. Lipopolysaccharide proved to be the primary receptor for kappa phage. Prodigiosin content of the lipopolysaccharide fraction was low.

Biosynthesis of prodigiosin by non-proliferating wild-type Serratia marcescens and mutants deficient in catabolism of alanine, histidine, and proline

Mutants of Serratia marcescens Nima, designated as Aut, Hut, or Put, did not utilize L-alanine, L-histidine, or L-proline, respectively, as a sole carbon source but did utilize other amino acids or glycerol as carbon sources. The bacteria were permeable to alanine, histidine, and proline but lacked the enzymes responsible for degradation of these amino acids. The Aut mutant contained no L-alanine dehydrogenase activity, whereas the Hut and Put mutants contained only 7 and 4% of the histidase and proline oxidase activities, respectively, found in the wild-type strain. Rates of oxygen uptake and protein synthesis were significantly lower when the mutants were incubated in the presence of amino acids they could not degrade. Studies of L-[14C]alanine, L-[14C]histidine, and L-[14C]proline incorporation into prodigiosin synthesized by these mutants and the wild-type strain revealed that proline was incorporated intact, whereas all of alanine except the carboxyl group was incorporated into the pigment molecule. Histidine did not enter prodigiosin directly. These data suggested that the presence of unique biosynthetic pathways, independent of primary metabolism, leads to formation of prodigiosin from specific amino acids.

Role of L-proline in the biosynthesis of prodigiosin

Nonproliferating cells of Serratia marcescens, wild-type strain Nima, synthesized the pigment, prodigiosin, when saline suspensions were incubated with aeration at 27 degrees C in the presence of proline or alanine. Mutants PutS1 and PutS2 derived from strain Nima formed prodigiosin from alanine, but not from proline, unless alanine also was added. Strain Nima utilized proline as a sole source of carbon and of nitrogen for growth, whereas Put mutants did not. Investigation of enzymes degrading proline showed that the wild-type strain contained proline oxidase, which was absent in Put mutants. The wild type, as well as the mutants, utilized alanine as the sole source of carbon and nitrogen for growth. Although nonproliferating cells of Put mutants failed to synthesize prodigiosin from proline, addition of L-[U-14C]proline to suspensions metabolizing and synthesizing the pigment because of addition of alanine resulted in the incorporation of radioactive label into prodigiosin, as well as into cellular protein. Since Put mutants could not catabolize proline, the incorporation of [14C]proline into the prodigiosin molecule indicated that proline was incorporated directly into the pigment.

Incorporation of proline into prodigiosin by a Put mutant of Serratia marcesens

A Put mutant of Serratia marcescens, deficient in proline oxidase and therefore unable to degrade proline, was used to assay for an enzymatic reaction responsible for incorporation of proline into prodigiosin. The reaction had a pH optimum of 7.5 and a Km of 1.1 X 10(-4) M at 27 C. At temperatures above 27 C, the velocity of the reaction decreased with increasing temperature and little activity was detected at 42 C. Activity of the enzyme was directly proportional to the quantity of pigment formed and was inhibited by thioproline, a substrate analog. These data suggested the presence of a unique and specific enzyme in the biosynthetic pathway for prodigiosin.

Macromolecular syntheses during biosynthesis of prodigiosin by Serratia marcescens

Amino acids that were utilized as sole sources of carbon and nitrogen for growth of Serratia marcescens Nima resulted in biosynthesis of prodigiosin in non-proliferating bacteria. Addition of alanine, proline, or histidine to non-proliferating cells incubated at 27 C increased the rate of protein synthesis and also caused biosynthesis of prodigiosin. No increase in the rate of protein synthesis was observed upon the addition of amino acids that did not stimulate prodigiosin biosynthesis. Increased rates of synthesis of ribonucleic acid (RNA) and of deoxyribonucleic acid (DNA) (a small amount) also occurred after addition of amino acids that resulted in biosynthesis of prodigiosin. After incubation of 24 h, the total amount of protein in suspensions of bacteria to which alanine or proline was added increased 67 and 98%, respectively. Total amounts of DNA and of RNA also increased before synthesis of prodigiosin. The amounts of these macromolecules did not increase after addition of amino acids that did not induce biosynthesis of progidiosin. However, macromolecular synthesis was not related only to prodigiosin biosynthesis because the rates of DNA, RNA, and protein synthesis also increased in suspensions of bacteria incubated with proline at 39 C, at which temperature no prodigiosin was synthesized. The quantities of DNA, RNA, and protein synthesized were lower in non-proliferating cells than in growing cells. The data indicated that amino acids causing biosynthesis of prodigiosin in non-proliferating cells must be metabolized and serve as sources of carbon and of nitrogen for synthesis of macromolecules and intermediates. Prodigiosin was synthesized secondarily to these primary metabolic events.

Prodigiosin-like pigments

Prodigiosin, the bright red tripyrrole pigment from Serratia marcescens, has also been identified in Pseudomonas magnesiorubra, Vibrio psychroerythrus, and two Gram-negative rod-shaped mesophilic marine bacteria not members of the genus Serratia. Prodigiosin is sometimes bound to proteins; thus, extracts may require acid treatment before isolation of the pigment. Higher homologs of prodigiosin have been detected by mass spectroscopy. A mutant strain of S. marcescens produced nor-prodigiosin, in which the methoxy group of prodigiosin is replaced by a hydroxy group. Another mutant strain produced a blue tetrapyrrole pigment whose structure is a dimer of prodigiosin's rings A and B. Three novel biosynthetic analogs of prodigiosin have been obtained using a colorless mutant which does make rings A and B but not ring C and which can couple rings A and B with some added monopyrroles similar to ring C. The structures of three prodiginine (prodigiosin-like) pigments from streptomyces have been elucidated. All have the methoxytripyrrole aromatic nucleus of prodigiosin and all have an 11 carbon aliphatic side chain attached at carbon 2 of ring C. In two of the pigments the side chain is also linked to another carbon of ring C. The earlier literature about prodiginine pigments from actinomycetes has been interpreted and evaluated in light of the most recent findings. The structure elucidation of six prodiginine pigments from Actinomadurae (Nocardiae) has been completed. Only one, undecylprodiginine, is the same as from a streptomycete. For three of the six pigments, nine carbon side chains are observed and in four of them the side chain is attached to carbon 5 of ring A as well as carbon 2 of ring C so that a large ring is formed which includes the three pyrrole moieties. A section on identification summarized useful methods and presents information with which any known prodiginine pigment can be identified. The final step in the biosynthesis of prodigiosin was known to be the coupling of methoxybipyrrolecarboxaldehyde (rings A and B) with methylpentylpyrrole (ring C). Recent work using 13C-labeled precursors and Fourier transform 13C nuclear magnetic resonance has shown the pattern of incorporation for acetate, proline, glycine, serine alanine, and methionine into prodigiosin. Each pyrrole ring is constructed in a different way. Two of the streptomyces pigments have also been investigated; the pattern of incorporation is similar to that for prodigiosin. The biological activities of some prodiginine pigments are summarized. All show activity against several Gram-positive bacteria; some have anti-malarial activity. Prodigiosin has been tested clinically against coccidioidomycosis.