The bacterial pigment xanthomonadin offers protection against photodamage

Description of Pseudomarimonas salicorniae sp. nov., Isolated from Salicornia herbacea L. in the Tidal Flat of the Yellow Sea

A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped, designated strain CAU 1642 T, was isolated from a Salicornia herbacea collected from a tidal flat in the Yellow Sea. Strain CAU 1642 T grew optimally at pH 8.0 and 30 °C. The highest 16S rRNA gene sequence similarity was 97.25%, with Pseudomarinomonas arenosa CAU 1598 T, and phylogenetic analysis indicated that strain CAU 1642 T belongs to the genus Pseudomarinomonas. The major cellular fatty acids were iso-C15:0, iso-C16:0, and summed feature 9 (iso-C17:1ω9c and/or 10-methyl C16:0). Ubiquinone-8 was the major respiratory quinone. The draft genome of strain CAU 1642 T was 4.5 Mb, with 68.7 mol% of G + C content. The phylogenetic, phenotypic, and chemotaxonomic analysis data reveal strain CAU 1642 T to be of a novel genus in the family Lysobacteraceae, with the proposed name Pseudomarinomonas salicorniae sp. nov. with type strain CAU 1642 T (= KCTC 92084 T = MCCC 1K07085T).

An insight into pathogenicity and virulence gene content of Xanthomonas spp. and its biocontrol strategies

The genus Xanthomonas primarily serves as a plant pathogen, targeting a diverse range of economically significant crops on a global scale. Xanthomonas spp. utilizes a collection of toxins, adhesins, and protein effectors as part of their toolkit to thrive in their surroundings, and establish themselves within plant hosts. The bacterial secretion systems (Type 1 to Type 6) assist in delivering the effector proteins to their intended destinations. These secretion systems are specialized multi-protein complexes responsible for transporting proteins into the extracellular milieu or directly into host cells. The potent virulence and systematic infection system result in rapid dissemination of the bacteria, posing significant challenges in management due to complexities and substantial loss incurred. Consequently, there has been a notable increase in the utilization of chemical pesticides, leading to bioaccumulation and raising concerns about adverse health effects. Biological control mechanisms through beneficial microorganism (Bacillus, Pseudomonas, Trichoderma, Burkholderia, AMF, etc.) have proven to be an appropriate alternative in integrative pest management system. This review details the pathogenicity and virulence factors of Xanthomonas, as well as its control strategies. It also encourages the use of biological control agents, which promotes sustainable and environmentally friendly agricultural practices.

Unlocking the genomic potential of Red Sea coral probiotics

The application of beneficial microorganisms for corals (BMC) decreases the bleaching susceptibility and mortality rate of corals. BMC selection is typically performed via molecular and biochemical assays, followed by genomic screening for BMC traits. Herein, we present a comprehensive in silico framework to explore a set of six putative BMC strains. We extracted high-quality DNA from coral samples collected from the Red Sea and performed PacBio sequencing. We identified BMC traits and mechanisms associated with each strain as well as proposed new traits and mechanisms, such as chemotaxis and the presence of phages and bioactive secondary metabolites. The presence of prophages in two of the six studied BMC strains suggests their possible distribution within beneficial bacteria. We also detected various secondary metabolites, such as terpenes, ectoines, lanthipeptides, and lasso peptides. These metabolites possess antimicrobial, antifungal, antiviral, anti-inflammatory, and antioxidant activities and play key roles in coral health by reducing the effects of heat stress, high salinity, reactive oxygen species, and radiation. Corals are currently facing unprecedented challenges, and our revised framework can help select more efficient BMC for use in studies on coral microbiome rehabilitation, coral resilience, and coral restoration.

Bacteria as a source of biopigments and their potential applications

From the prehistoric period, the utilization of pigments as colouring agents was an integral part of human life. Early people may have utilized paint for aesthetic motives, according to archaeologists. The pigments are either naturally derived or synthesized in the laboratory. Different studies reported that certain synthetic colouring compounds were toxic and had adverse health and environmental effects. Therefore, knowing the drawbacks of these synthetic colouring agents now scientists are attracted towards the harmless natural pigments. The main sources of natural pigments are plants, animals or microorganisms. Out of these natural pigments, microorganisms are the most important source for the production and application of bioactive secondary metabolites. Among all kinds of microorganisms, bacteria have specific benefits due to their short life cycle, low sensitivity to seasonal and climatic variations, ease of scaling, and ability to create pigments of various colours. Based on these physical characteristics, bacterial pigments appear to be a promising sector for novel biotechnological applications, ranging from functional food production to the development of new pharmaceuticals and biomedical therapies. This review summarizes the need for bacterial pigments, biosynthetic pathways of carotenoids and different applications of bacterial pigments.

Bacterial Pigments and Their Multifaceted Roles in Contemporary Biotechnology and Pharmacological Applications

Synthetic dyes and colourants have been the mainstay of the pigment industry for decades. Researchers are eager to find a more environment friendly and non-toxic substitute because these synthetic dyes have a negative impact on the environment and people’s health. Microbial pigments might be an alternative to synthetic pigments. Microbial pigments are categorized as secondary metabolites and are mainly produced due to impaired metabolism under stressful conditions. These pigments have vibrant shades and possess nutritional and therapeutic properties compared to synthetic pigment. Microbial pigments are now widely used within the pharmaceuticals, food, paints, and textile industries. The pharmaceutical industries currently use bacterial pigments as a medicine alternative for cancer and many other bacterial infections. Their growing popularity is a result of their low cost, biodegradable, non-carcinogenic, and environmentally beneficial attributes. This audit article has made an effort to take an in-depth look into the existing uses of bacterial pigments in the food and pharmaceutical industries and project their potential future applications.

Luteibacter flocculans sp. nov., Isolated from a Eutrophic Pond and Isolation and Characterization of Luteibacter Phage vB_LflM-Pluto

Luteibacter is a genus of the Rhodanobacteraceae family. The present study describes a novel species within the genus Luteibacter (EIF3^T). The strain was analyzed genomically, morphologically and physiologically. Average nucleotide identity analysis revealed that it is a new species of Luteibacter. In silico analysis indicated two putative prophages (one incomplete, one intact). EIF3^T cells form an elliptical morphotype with an average length of 2.0 µm and width of 0.7 µm and multiple flagella at one end. The bacterial strain is an aerobic Gram-negative with optimal growth at 30 °C. EIF3^T is resistant towards erythromycin, tetracycline and vancomycin. We propose the name Luteibacter flocculans sp. nov. with EIF3^T (=DSM 112537^T = LMG 32416^T) as type strain. Further, we describe the first known Luteibacter-associated bacteriophage called vB_LflM-Pluto.

Nature's palette: An emerging frontier for coloring dairy products

Consumers all across the world are looking for the most delectable and appealing foods, while also demanding products that are safer, more nutritious, and healthier. Substitution of synthetic colorants with natural colorants has piqued consumer and market interest in recent years. Due to increasing demand, extensive research has been conducted to find natural and safe food additives, such as natural pigments, that may have health benefits. Natural colorants are made up of a variety of pigments, many of which have significant biological potential. Because of the promising health advantages, natural colorants are gaining immense interest in the dairy industry. This review goes over the use of various natural colorants in dairy products which can provide desirable color as well as positive health impacts. The purpose of this review is to provide an in-depth look into the field of food (natural or synthetic) colorants applied in dairy products as well as their potential health benefits, safety, general trends, and future prospects  in food science and technology. In this paper, we listed a plethora of applications of natural colorants in various milk-based products.

Comparative genomics provides insights into the potential biocontrol mechanism of two Lysobacter enzymogenes strains with distinct antagonistic activities

Lysobacter enzymogenes has been applied as an abundant beneficial microorganism to control plant disease; however, most L. enzymogenes strains have been mainly reported to control fungal diseases, not bacterial diseases. In this study, two L. enzymogenes strains were characterized, of which CX03 displayed a broad spectrum of antagonistic activities toward multiple bacteria, while CX06 exhibited a broad spectrum of antagonistic activities toward diverse fungi and oomycete, and the whole genomes of the two strains were sequenced and compared. The genome annotation showed that the CX03 genome comprised a 5,947,018 bp circular chromosome, while strain CX06 comprised a circular 6,206,196 bp chromosome. Phylogenetic analysis revealed that CX03 had a closer genetic relationship with L. enzymogenes ATCC29487T and M497-1, while CX06 was highly similar to L. enzymogenes C3. Functional gene annotation analyses of the two L. enzymogenes strains showed that many genes or gene clusters associated with the biosynthesis of different secondary metabolites were found in strains CX03 and CX06, which may be responsible for the different antagonistic activities against diverse plant pathogens. Moreover, comparative genomic analysis revealed the difference in bacterial secretory systems between L. enzymogenes strains CX03 and CX06. In addition, numerous conserved genes related to siderophore biosynthesis, quorum sensing, two-component systems, flagellar biosynthesis and chemotaxis were also identified in the genomes of strains CX03 and CX06. Most reported L. enzymogenes strains were proven mainly to suppress fungi, while CX03 exhibited direct inhibitory activities toward plant bacterial pathogens and showed an obvious role in managing bacterial disease. This study provides a novel understanding of the biocontrol mechanisms of L. enzymogenes, and reveals great potential for its application in plant disease control.

Comparative Genomic Analysis of the Lettuce Bacterial Leaf Spot Pathogen, Xanthomonas hortorum pv. vitians, to Investigate Race Specificity

Bacterial leaf spot (BLS) of lettuce caused by Xanthomonas hortorum pv. vitians (Xhv) was first described over 100 years ago and remains a significant threat to lettuce cultivation today. This study investigated the genetic relatedness of the Xhv strains and the possible genetic sources of this race-specific pathogenicity. Whole genome sequences of eighteen Xhv strains representing the three races, along with eight related Xanthomonas strains, were included in the analysis. A maximum likelihood phylogeny based on concatenated whole genome SNPs confirmed previous results describing two major lineages of Xhv strains. Gene clusters encoding secretion systems, secondary metabolites, and bacteriocins were assessed to identify putative virulence factors that distinguish the Xhv races. Genome sequences were mined for effector genes, which have been shown to be involved in race specificity in other systems. Two effectors identified in this study, xopAQ and the novel variant xopAF2, were revealed as possible mediators of a gene-for-gene interaction between Xhv race 1 and 3 strains and wild lettuce Lactuca serriola ARM-09-161-10-1. Transposase sequence identified downstream of xopAF2 and prophage sequence found nearby within Xhv race 1 and 3 insertion sequences suggest that this gene may have been acquired through phage-mediated gene transfer. No other factors were identified from these analyses that distinguish the Xhv races.

HetI-Like Phosphopantetheinyl Transferase Posttranslationally Modifies Acyl Carrier Proteins in Xanthomonas spp

In Xanthomonas spp., the biosynthesis of the yellow pigment xanthomonadin and fatty acids originates in the type II polyketide synthase (PKS II) and fatty acid synthase (FAS) pathways, respectively. The acyl carrier protein (ACP) is the central component of PKS II and FAS and requires posttranslational phosphopantetheinylation to initiate these pathways. In this study, for the first time, we demonstrate that the posttranslational modification of ACPs in X. campestris pv. campestris is performed by an essential 4'-phosphopantetheinyl transferase (PPTase), XcHetI (encoded by Xc_4132). X. campestris pv. campestris strain XchetI could not be deleted from the X. campestris pv. campestris genome unless another PPTase-encoding gene such as Escherichia coli acpS or Pseudomonas aeruginosa pcpS was present. Compared with wild-type strain X. campestris pv. campestris 8004 and mutant XchetI::PapcpS, strain XchetI::EcacpS failed to generate xanthomonadin pigments and displayed reduced pathogenicity for the host plant, Brassica oleracea. Further experiments showed that the expression of XchetI restored the growth of E. coli acpS mutant HT253 and, when a plasmid bearing XchetI was introduced into P. aeruginosa, pcpS, which encodes the sole PPTase in P. aeruginosa, could be deleted. In in vitro enzymatic assays, XcHetI catalyzed the transformation of 4'-phosphopantetheine from coenzyme A to two X. campestris pv. campestris apo-acyl carrier proteins, XcAcpP and XcAcpC. All of these findings indicate that XcHetI is a surfactin PPTase-like PPTase with a broad substrate preference. Moreover, the HetI-like PPTase is ubiquitously conserved in Xanthomonas spp., making it a potential new drug target for the prevention of plant diseases caused by Xanthomonas.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Antibacterial, anti-biofilm, and anti-virulence potential of tea tree oil against leaf blight pathogen Xanthomonas oryzae pv. oryzae instigates disease suppression

Bacterial leaf blight (BLB) disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), causes major annual economic losses around the world. Inorganic copper compounds and antibiotics are conventionally used to control BLB disease. They often cause environmental pollution, contributing to adverse effects on human health. Therefore, research is now leading to the search for alternative control methods. Tea tree oil (TTO) is obtained from a traditional medicinal plant, Melaleuca alternifolia, with antibacterial properties. In this study, we found that TTO showed antibacterial activity against Xoo with a minimum inhibitory concentration (MIC) of 18 mg/ml. These antagonistic activities were not limited only to planktonic cells, as further studies have shown that TTO effectively eradicated sessile cells of Xoo in both initial and mature biofilms. Furthermore, it was also observed that TTO reduced various key virulence properties of Xoo, such as swimming, swarming motility, and the production of extracellular polymeric substances, xanthomonadin, and exoenzymes. TTO triggered ROS generation with cell membrane damage as an antibacterial mode of action against Xoo. The in silico study revealed that 1,8-cineole of TTO was effectively bound to two essential proteins, phosphoglucomutase and peptide deformylase, responsible for the synthesis of EPS and bacterial survival, respectively. These antibacterial and anti-virulence activities of TTO against Xoo were further confirmed by an ex vivo virulence assay where TTO significantly reduced the lesion length caused by Xoo on rice leaves. All these data concluded that TTO could be a safe, environment-friendly alternative approach for the comprehensive management of BLB disease.

Biogeography of Bacterial Communities and Specialized Metabolism in Human Aerodigestive Tract Microbiomes

The aerodigestive tract (ADT) is the primary portal through which pathogens and other invading microbes enter the body. As the direct interface with the environment, we hypothesize that the ADT microbiota possess biosynthetic gene clusters (BGCs) for antibiotics and other specialized metabolites to compete with both endogenous and exogenous microbes. From 1,214 bacterial genomes, representing 136 genera and 387 species that colonize the ADT, we identified 3,895 BGCs. To determine the distribution of BGCs and bacteria in different ADT sites, we aligned 1,424 metagenomes, from nine different ADT sites, onto the predicted BGCs. We show that alpha diversity varies across the ADT and that each site is associated with distinct bacterial communities and BGCs. We identify specific BGC families enriched in the buccal mucosa, external naris, gingiva, and tongue dorsum despite these sites harboring closely related bacteria. We reveal BGC enrichment patterns indicative of the ecology at each site. For instance, aryl polyene and resorcinol BGCs are enriched in the gingiva and tongue, which are colonized by many anaerobes. In addition, we find that streptococci colonizing the tongue and cheek possess different ribosomally synthesized and posttranslationally modified peptide BGCs. Finally, we highlight bacterial genera with BGCs but are underexplored for specialized metabolism and demonstrate the bioactivity of Actinomyces against other bacteria, including human pathogens. Together, our results demonstrate that specialized metabolism in the ADT is extensive and that by exploring these microbiomes further, we will better understand the ecology and biogeography of this system and identify new bioactive natural products.

IMPORTANCE Bacteria produce specialized metabolites to compete with other microbes. Though the biological activities of many specialized metabolites have been determined, our understanding of their ecology is limited, particularly within the human microbiome. As the aerodigestive tract (ADT) faces the external environment, bacteria colonizing this tract must compete both among themselves and with invading microbes, including human pathogens. We analyzed the genomes of ADT bacteria to identify biosynthetic gene clusters (BGCs) for specialized metabolites. We found that the majority of ADT BGCs are uncharacterized and the metabolites they encode are unknown. We mapped the distribution of BGCs across the ADT and determined that each site is associated with its own distinct bacterial community and BGCs. By further characterizing these BGCs, we will inform our understanding of ecology and biogeography across the ADT, and we may uncover new specialized metabolites, including antibiotics.

Deep phylo-taxono genomics reveals Xylella as a variant lineage of plant associated Xanthomonas and supports their taxonomic reunification along with Stenotrophomonas and Pseudoxanthomonas

Genus Xanthomonas is a group of phytopathogens that is phylogenetically related to Xylella, Stenotrophomonas, and Pseudoxanthomonas, having diverse lifestyles. Xylella is a lethal plant pathogen with a highly reduced genome, atypical GC content and is taxonomically related to these three genera. Deep phylo-taxono genomics reveals that Xylella is a variant Xanthomonas lineage that is sandwiched between Xanthomonas clades. Comparative studies suggest the role of unique pigment and exopolysaccharide gene clusters in the emergence of Xanthomonas and Xylella clades. Pan-genome analysis identified a set of unique genes associated with sub-lineages representing plant-associated Xanthomonas clade and nosocomial origin Stenotrophomonas clade. Overall, our study reveals the importance of reconciling classical phenotypic data and genomic findings in reconstituting the taxonomic status of these four genera. SIGNIFICANCE STATEMENT: Xylella fastidiosa is a devastating pathogen of perennial dicots such as grapes, citrus, coffee, and olives. An insect vector transmits the pathogen to its specific host wherein the infection leads to complete wilting of the plants. The genome of X. fastidiosa is significantly reduced both in terms of size (2 Mb) and GC content (50%) when compared with its relatives such as Xanthomonas, Stenotrophomonas, and Pseudoxanthomonas that have higher GC content (65%) and larger genomes (5 Mb). In this study, using systematic and in-depth genome-based taxonomic and phylogenetic criteria and comparative studies, we assert the need to unify Xanthomonas with its relatives (Xylella, Stenotrophomonas and Pseudoxanthomonas). Interestingly, Xylella revealed itself as a minor variant lineage embedded within two major Xanthomonas lineages comprising member species of different hosts.

Escherichia coli Nissle 1917 secondary metabolism: aryl polyene biosynthesis and phosphopantetheinyl transferase crosstalk

Escherichia coli Nissle 1917 (EcN) is a Gram-negative bacterium that is used to treat inflammatory bowel diseases. The probiotic character of EcN is not well-understood, but its ability to produce secondary metabolites plays an important role in its activity. The EcN genome encodes for an aryl polyene (APE) biosynthetic gene cluster (BGC), and APE products have a role in biofilm formation. We show here that this unusual polyketide assembly line synthase produces four APE molecules which are likely cis/trans isomers. Within the APE BGC, two acyl carrier proteins are involved in biosynthesis. Acyl carrier proteins require activation by post-translational modification with a phosphopantetheinyl transferase (PPTase). Through analysis of single, double, and triple mutants of three PPTases, the PPTase-BGC crosstalk relationship in EcN was characterized. Understanding PPTase-BGC crosstalk is important for the engineering of secondary metabolite production hosts and for targeting of PPTases with new antibiotics. KEY POINTS: • Escherichia coli Nissle 1917 biosynthesizes four aryl polyene isoforms. • Phosphopantetheinyl transferase crosstalk is important for biosynthesis.

Identification of essential genes for Escherichia coli aryl polyene biosynthesis and function in biofilm formation

Aryl polyenes (APEs) are specialized polyunsaturated carboxylic acids that were identified in silico as the product of the most widespread family of bacterial biosynthetic gene clusters (BGCs). They are present in several Gram-negative host-associated bacteria, including multidrug-resistant human pathogens. Here, we characterize a biological function of APEs, focusing on the BGC from a uropathogenic Escherichia coli (UPEC) strain. We first perform a genetic deletion analysis to identify the essential genes required for APE biosynthesis. Next, we show that APEs function as fitness factors that increase protection from oxidative stress and contribute to biofilm formation. Together, our study highlights key steps in the APE biosynthesis pathway that can be explored as potential drug targets for complementary strategies to reduce fitness and prevent biofilm formation of multi-drug resistant pathogens.

Foliar Application or Seed Priming of Cholic Acid-Glycine Conjugates can Mitigate/Prevent the Rice Bacterial Leaf Blight Disease via Activating Plant Defense Genes

Xanthomonas Oryzae pv. oryzae (Xoo) causes bacterial blight and Rhizoctonia solani (R. solani) causes sheath blight in rice accounting for >75% of crop losses. Therefore, there is an urgent need to develop strategies for the mitigation of these pathogen infections. In this study, we report the antimicrobial efficacy of Cholic Acid-Glycine Conjugates (CAGCs) against Xoo and R. solani. We show that CAGC C6 is a broad-spectrum antimicrobial and is also able to degrade biofilms. The application of C6 did not hamper plant growth and showed minimal effect on the plant cell membranes. Exogenous application of C6 on pre-infection or post-infection of Xoo on rice susceptible genotype Taichung native (TN1) can mitigate the bacterial load and improve resistance through upregulation of plant defense genes. We further demonstrate that C6 can induce plant defense responses when seeds were primed with C6 CAGC. Therefore, this study demonstrates the potential of CAGCs as effective antimicrobials for crop protection that can be further explored for field applications.

Brought to you courtesy of the red, white, and blue-pigments of nontuberculous mycobacteria

Pigments are chromophores naturally synthesized by animals, plants, and microorganisms, as well as produced synthetically for a wide variety of industries such as food, pharmaceuticals, and textiles. Bacteria produce various pigments including melanin, pyocyanin, bacteriochlorophyll, violacein, prodigiosin, and carotenoids that exert diverse biological activities as antioxidants and demonstrate anti-inflammatory, anti-cancer, and antimicrobial properties. Nontuberculous mycobacteria (NTM) include over 200 environmental and acid-fast species; some of which can cause opportunistic disease in humans. Early in the study of mycobacteriology, the vast majority of mycobacteria were not known to synthesize pigments, particularly NTM isolates of clinical significance such as the Mycobacterium avium complex (MAC) species. This paper reviews the overall understanding of microbial pigments, their applications, as well as highlights what is currently known about pigments produced by NTM, the circumstances that trigger their production, and their potential roles in NTM survival and virulence.

Synergistic consortium of beneficial microorganisms in rice rhizosphere promotes host defense to blight-causing Xanthomonas oryzae pv. oryzae

Rice plants primed with beneficial microbes Bacillus amyloliquefaciens and Aspergillus spinulosporus with biocontrol potential against Xanthomonas oryzae pv. oryzae, provided protection from disease by reprogramming host defence response under pathogen challenge. Plant-beneficial microbe interactions taking place in the rhizosphere are widely used for growth promotion and mitigation of biotic stresses in plants. The present study aims to evaluate the defense network induced by beneficial microorganisms in the rice rhizosphere, and the three-way interaction involved upon inoculation with dreadful bacteria Xanthomonas oryzae pv. oryzae (Xoo). Differential expression of defense-related enzymes, proteins, and genes in rice variety Swarna primed with a microbial consortium of Bacillus amyloliquefaciens and Aspergillus spinulosporus were quantified in the presence and absence of Xoo. The time-based expression profile alterations in leaves under the five distinct treatments "(unprimed unchallenged, unprimed Xoo challenged, B. amyloliquefaciens primed and challenged, A. spinulosporus primed and challenged, B. amyloliquefaciens and A. spinulosporus consortium primed and challenged)" revealed differential early upregulation of SOD, PAL, PO, PPO activities and TPC content in beneficial microbes primed plants in comparison to unprimed challenged plants. The enhanced defense response in all the rice plants recruited with beneficial microbe was also reflected by reduced plant mortality and an increased plant dry biomass and chlorophyll content. Also, more than 550 protein spots were observed per gel by PD Quest software, a total of 55 differentially expressed protein spots were analysed used MALDI-TOF MS, out of which 48 spots were recognized with a significant score with direct or supporting roles in stress alleviation and disease resistance. qRT-PCR was carried out to compare the biochemical and proteomic data to mRNA levels. We conclude that protein biogenesis and alleviated resistance response may contribute to improved biotic stress adaptation. These results might accelerate the functional regulation of the Xoo-receptive proteins in the presence of beneficial rhizospheric microbes and their computation as promising molecular markers for superior disease management.

Allelochemical catechol comprehensively impedes bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae (Xoo) induces bacterial leaf blight (BLB), is known to be the most devastating disease of rice. The present investigation for the first time explains the antibacterial, anti-biofilm, and antivirulence potential of the simplest allelochemical catechol. Bacterial viability and growth are significantly reducing in catechol treatment. Further study also reveals that catechol also inhibits primary attachment and preformed biofilm of Xoo even at half MIC concentration. The half MIC concentration of catechol also induce a significant decrease in virulence factors like swimming, swarming, exopolysaccharide, and xanthomonadin production. Next, we investigate the possible antibacterial mode of action of catechol against Xoo. Results show that, the catechol caused oxidative stress and targets cell membrane for its antibacterial activity. Whereas, in silico study reveals that, catechol binds with the catalytic domain of XanA protein and this may be consider as a reason for antibiofilm activity of catechol. Moreover, in virulence assay on rice plants, we observe significant decrement in lesion length in catechol and Xoo co-treated rice leaves as compared with only Xoo treated leaves. All the results clearly show, allelochemical catechol to be a potential compound for the antibacterial, anti-biofilm, and antivirulence agent against Xoo and consequently mitigating the BLB disease advancement in rice.

Biodiversity and Habitats of Polar Region Polyhydroxyalkanoic Acid-Producing Bacteria: Bioprospection by Popular Screening Methods

Polyhydroxyalkanoates (PHAs), the intracellular polymers produced by various microorganisms as carbon and energy storage, are of great technological potential as biodegradable versions of common plastics. PHA-producing microbes are therefore in great demand and a plethora of different environments, especially extreme habitats, have been probed for the presence of PHA-accumulators. However, the polar region has been neglected in this regard, probably due to the low accessibility of the sampling material and unusual cultivation regime. Here, we present the results of a screening procedure involving 200 bacterial strains isolated from 25 habitats of both polar regions. Agar-based tests, microscopy, and genetic methods were conducted to elucidate the biodiversity and potential of polar-region PHA-accumulators. Microscopic observation of Nile Red stained cells proved to be the most reliable screening method as it allowed to confirm the characteristic bright orange glow of the Nile Red–PHA complex as well as the typical morphology of the PHA inclusions. Psychrophilic PHA-producers belonged mostly to the Comamonadaceae family (Betaproteobacteria) although actinobacterial PHA synthesizers of the families, Microbacteriaceae and Micrococcaceae also featured prominently. Glacial and postglacial habitats as well as developed polar region soils, were evaluated as promising for PHA-producer bioprospection. This study highlights the importance of psychrophiles as biodiverse and potent polyhydroxyalkanoate sources for scientific and application-aimed research.

Chemical Structure, Biological Roles, Biosynthesis and Regulation of the Yellow Xanthomonadin Pigments in the Phytopathogenic Genus Xanthomonas

Xanthomonadins are membrane-bound yellow pigments that are typically produced by phytopathogenic bacterial Xanthomonas spp., Xylella fastidiosa, and Pseudoxanthomonas spp. They are also produced by a diversity of environmental bacterial species. Considerable research has revealed that they are a unique group of halogenated, aryl-polyene, water-insoluble pigments. Xanthomonadins have been shown to play important roles in epiphytic survival and host-pathogen interactions in the phytopathogen Xanthomonas campestris pv. campestris, which is the causal agent of black rot in crucifers. Here, we review recent advances in the understanding of xanthomonadin chemical structures, physiological roles, biosynthetic pathways, regulatory mechanisms, and crosstalk with other signaling pathways. The aim of the present review is to provide clues for further in-depth research on xanthomonadins from Xanthomonas and other related bacterial species.

Friend or foe? Exploring the fine line between Pseudomonas brassicacearum and phytopathogens

Pseudomonas brassicacearum is one of over fifty species of bacteria classified into the P. fluorescens group. Generally considered a harmless commensal, these bacteria are studied for their plant-growth promotion (PGP) and biocontrol characteristics. Intriguingly, P. brassicacearum is closely related to P. corrugata , which is classified as an opportunistic phytopathogen. Twenty-one P. brassicacearum genomes have been sequenced to date. In the current review, genomes of P. brassicacearum and strains from the P. corrugata clade were mined for regions associated with PGP, biocontrol and pathogenicity. We discovered that ‘beneficial’ bacteria and those classified as plant pathogens have many genes in common; thus, only a fine line separates beneficial/harmless commensals from those capable of causing disease in plants. The genotype and physiological state of the plant, the presence of biotic/abiotic stressors, and the ability of bacteria to manipulate the plant immune system collectively contribute to how the bacterial-plant interaction plays out. Because production of extracellular metabolites is energetically costly, these compounds are expected to impart a fitness advantage to the producer. P. brassicacearum is able to reduce the threat of nematode predation through release of metabolites involved in biocontrol. Moreover this bacterium has the unique ability to form biofilms on the head of Caenorhabditis elegans, as a second mechanism of predator avoidance. Rhizobacteria, plants, fungi, and microfaunal predators have occupied a shared niche for millions of years and, in many ways, they function as a single organism. Accordingly, it is essential that we appreciate the dynamic interplay among these members of the community.

Genetic Interference Analysis Reveals that Both 3-Hydroxybenzoic Acid and 4-Hydroxybenzoic Acid Are Involved in Xanthomonadin Biosynthesis in the Phytopathogen Xanthomonas campestris pv. campestris

A characteristic feature of phytopathogenic Xanthomonas bacteria is the production of yellow membrane-bound pigments called xanthomonadins. Previous studies showed that 3-hydroxybenzoic acid (3-HBA) was a xanthomonadin biosynthetic intermediate and also, that it had a signaling role. The question of whether the structural isomers 4-HBA and 2-HBA (salicylic acid) have any role in xanthomonadin biosynthesis remained unclear. In this study, we have selectively eliminated 3-HBA, 4-HBA, or the production of both by expression of the mhb, pobA, and pchAB gene clusters in the Xanthomonas campestris pv. campestris strain XC1. The resulting strains were different in pigmentation, virulence factor production, and virulence. These results suggest that both 3-HBA and 4-HBA are involved in xanthomonadin biosynthesis. When both 3-HBA and 4-HBA are present, X. campestris pv. campestris prefers 3-HBA for Xanthomonadin-A biosynthesis; the 3-HBA-derived Xanthomonadin-A was predominant over the 4-HBA-derived xanthomonadin in the wild-type strain XC1. If 3-HBA is not present, then 4-HBA is used for biosynthesis of a structurally uncharacterized Xanthomonadin-B. Salicylic acid had no effect on xanthomonadin biosynthesis. Interference with 3-HBA and 4-HBA biosynthesis also affected X. campestris pv. campestris virulence factor production and reduced virulence in cabbage and Chinese radish. These findings add to our understanding of xanthomonadin biosynthetic mechanisms and further help to elucidate the biological roles of xanthomonadins in X. campestris pv. campestris adaptation and virulence in host plants.

The cyl Genes Reveal the Biosynthetic and Evolutionary Origins of the Group B Streptococcus Hemolytic Lipid, Granadaene

Group B Streptococcus (GBS) is a β-hemolytic, Gram-positive bacterium that commonly colonizes the female lower genital tract and is associated with fetal injury, preterm birth, spontaneous abortion, and neonatal infections. A major factor promoting GBS virulence is the β-hemolysin/cytolysin, which is cytotoxic to several host cells. We recently showed that the ornithine rhamnolipid pigment, Granadaene, produced by the gene products of the cyl operon, is hemolytic. Here, we demonstrate that heterologous expression of the GBS cyl operon conferred hemolysis, pigmentation, and cytoxicity to Lactococcus lactis, a model non-hemolytic Gram-positive bacterium. Similarly, pigment purified from L. lactis is hemolytic, cytolytic, and identical in structure to Granadaene extracted from GBS, indicating the cyl operon is sufficient for Granadaene production in a heterologous host. Using a systematic survey of phyletic patterns and contextual associations of the cyl genes, we identify homologs of the cyl operon in physiologically diverse Gram-positive bacteria and propose undescribed functions of cyl gene products. Together, these findings bring greater understanding to the biosynthesis and evolutionary foundations of a key GBS virulence factor and suggest that such potentially toxic lipids may be encoded by other bacteria.

Using Nature's polyenes as templates: studies of synthetic xanthomonadin analogues and realising their potential as antioxidants

Two truncated analogues of the polyenyl photoprotective xanthomonadin pigments have been synthesised utilising an iterative Heck-Mizoroki (HM)/iododeboronation cross coupling approach and investigated as models of the natural product photoprotective agents in bacteria. Despite the instability of these types of compounds, both analogues proved to be sufficiently stable to allow isolation, spectroscopic analysis and biological studies of their photoprotective behaviour which showed that despite their shorter polyene chain length, they retained the ability to protect bacteria from photochemical damage; i.e. incorporation of one compound into E. coli provided photoprotective activity against singlet oxygen analogous to the natural photoprotective mechanisms employed by Xanthomonas bacteria, answering key questions about what minimal functionality is required to impart photoprotection, potentially leading to new classes of photoprotective and antioxidants compounds.

A novel 3-oxoacyl-ACP reductase (FabG3) is involved in the xanthomonadin biosynthesis of Xanthomonas campestris pv. campestris

Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot in crucifers, produces a membrane-bound yellow pigment called xanthomonadin to protect against photobiological and peroxidative damage, and uses a quorum-sensing mechanism mediated by the diffusible signal factor (DSF) family signals to regulate virulence factors production. The Xcc gene XCC4003, annotated as Xcc fabG3, is located in the pig cluster, which may be responsible for xanthomonadin synthesis. We report that fabG3 expression restored the growth of the Escherichia coli fabG temperature-sensitive mutant CL104 under non-permissive conditions. In vitro assays demonstrated that FabG3 catalyses the reduction of 3-oxoacyl-acyl carrier protein (ACP) intermediates in fatty acid synthetic reactions, although FabG3 had a lower activity than FabG1. Moreover, the fabG3 deletion did not affect growth or fatty acid composition. These results indicate that Xcc fabG3 encodes a 3-oxoacyl-ACP reductase, but is not essential for growth or fatty acid synthesis. However, the Xcc fabG3 knock-out mutant abolished xanthomonadin production, which could be only restored by wild-type fabG3, but not by other 3-oxoacyl-ACP reductase-encoding genes, indicating that Xcc FabG3 is specifically involved in xanthomonadin biosynthesis. Additionally, our study also shows that the Xcc fabG3-disrupted mutant affects Xcc virulence in host plants.

Microbial Pigments in the Food Industry-Challenges and the Way Forward

Developing new colors for the food industry is challenging, as colorants need to be compatible with a food flavors, safety, and nutritional value, and which ultimately have a minimal impact on the price of the product. In addition, food colorants should preferably be natural rather than synthetic compounds. Micro-organisms already produce industrially useful natural colorants such as carotenoids and anthocyanins. Microbial food colorants can be produced at scale at relatively low costs. This review highlights the significance of color in the food industry, why there is a need to shift to natural food colors compared to synthetic ones and how using microbial pigments as food colorants, instead of colors from other natural sources, is a preferable option. We also summarize the microbial derived food colorants currently used and discuss their classification based on their chemical structure. Finally, we discuss the challenges faced by the use and development of food grade microbial pigments and how to deal with these challenges, using advanced techniques including metabolic engineering and nanotechnology.

Bacterial Pigments: The Bioactivities and as an Alternative for Therapeutic Applications

Synthetic pigments have been widely used in various applications since the 1980s. However, the hyperallergenicity or carcinogenicity effects of synthetic dyes have led to the increased research on natural pigments. Among the natural resources, bacterial pigments are a good alternative to synthetic pigments because of their significant properties. Bacterial pigments are also one of the emerging fields of research since it offers promising opportunities for different applications. Besides its use as safe coloring agents in the cosmetic and food industry, bacterial pigments also possess biological properties such as antimicrobial, antiviral, antioxidant and anticancer activities. This review article highlights the various types of bacterial pigments, the latest studies on the discovery of bacterial pigments and the therapeutic insights of these bacterial pigments which hopefully provides useful information, guidance and improvement in future study.

Biosynthesis of the yellow xanthomonadin pigments involves an ATP-dependent 3-hydroxybenzoic acid: acyl carrier protein ligase and an unusual type II polyketide synthase pathway

Xanthomonadins are yellow pigments that are produced by the phytopathogen Xanthomonas campestris pv. campestris (Xcc). A pig cluster is responsible for xanthomonadin biosynthesis. Previously, Xcc4014 of the cluster was characterized as a bifunctional chorismatase that produces 3-hydroxybenzoic acid (3-HBA) and 4-HBA. In this study, genetic analysis identified 11 genes within the pig cluster to be essential for xanthomonadin biosynthesis. Biochemical and bioinformatics analysis suggest that xanthomonadins are synthesized via an unusual type II polyketide synthase pathway. Heterologous expression of the pig cluster in non-xanthomonadin-producing Pseudomonas aeruginosa strain resulted in the synthesis of chlorinated xanthomonadin-like pigments. Further analysis showed that xanC encodes an acyl carrier protein (ACP) while xanA2 encodes a ATP-dependent 3-HBA:ACP ligase. Both of them act together to catalyse the formation of 3-HBA-S-ACP from 3-HBA to initiate xanthomonadin biosynthesis. Finally, we showed that xanH encodes a FabG-like enzyme and xanK encodes a novel glycosyltransferase. Both xanH and xanK are not only required for xanthomonadin biosynthesis, but also required for the balanced biosynthesis of extracellular polysaccharides and DSF-family quorum sensing signals. These findings provide us with a better understanding of xanthomonadin biosynthetic mechanisms and directly demonstrate the presence of extensive cross-talk among xanthomonadin biosynthetic pathways and other metabolic pathways.

Pigments from Soil Bacteria and Their Therapeutic Properties: A Mini Review

Advancement in research on dyes obtained from natural sources e.g., plants, animals, insects and micro-organisms is widening the application of natural dyes in various fields. The natural dyes substituted their synthetic analogs at the beginning of twentieth century due to their improved quality, value, ease of production, ease of dyeing and some other factors. This era of dominance ended soon when toxic effects of synthetic dyes were reported. In the last few decades, pigments from micro-organisms especially soil derived bacteria is replacing dyes from other natural sources because of the increasing demand for safe, non-toxic, and biodegradable natural product. Apart from application in agriculture practices, cosmetics, textile, food and paper industries, bacterial pigments have additional biological activities e.g., anti-tumor, anti-fungal, anti-bacterial, immunosuppressive anti-viral, and many more which make them a potential candidate for pharmaceutical industry. Optimization of culture conditions and fermentation medium is the key strategies for large scale production of these natural dyes. An effort has been done to give an overview of pigments obtained from bacteria of soil origin, their dominance over dyes from other sources (natural and synthetic) and applications in the medical world in the underlying study.

Insights Into the Roles of Two Genes of the Histidine Biosynthesis Operon in Pathogenicity of Xanthomonas oryzae pv. oryzicola

Xanthomonas oryzae pv. oryzicola is an X. oryzae pathovar that causes bacterial leaf streak in rice. In this study, we performed functional characterization of a nine-gene his operon in X. oryzae pv. oryzicola. Sequence analysis indicates that this operon is highly conserved in Xanthomonas spp. Auxotrophic assays confirmed that the his operon was involved in histidine biosynthesis. We found that two genes within this operon, trpR and hisB, were required for virulence and bacterial growth in planta. Further research revealed that trpR and hisB play different roles in X. oryzae pv. oryzicola. The trpR acts as a transcriptional repressor and could negatively regulate the expression of hisG, -D, -C, -B, -H, -A, and -F. hisB, which encodes a bifunctional enzyme implicated in histidine biosynthesis, was shown to be required for xanthomonadin production in X. oryzae pv. oryzicola. The disruption of hisB reduced the transcriptional expression of five known shikimate pathway-related genes xanB2, aroE, aroA, aroC, and aroK. We found that the his operon in X. oryzae pv. oryzicola is not involved in hypersensitive response in nonhost tobacco plants. Collectively, our results revealed that two genes in histidine biosynthesis operon play an important role in the pathogenicity of X. oryzae pv. oryzicola Rs105.

Identification of a fabZ gene essential for flexirubin synthesis in Cytophaga hutchinsonii

Cytophaga hutchinsonii, an aerobic soil bacterium which could degrade cellulose, produces yellow flexirubin pigments. In this study, fabZ, annotated as a putative β-hydroxyacyl-(acyl carrier protein) (ACP) dehydratase gene, was identified by insertional mutation and gene deletion as an essential gene for flexirubin pigment synthesis. The availability of a FabZ mutant that fails to produce flexirubin allowed us to investigate the biological role of the pigment in C. hutchinsonii. Loss of flexirubin made the FabZ mutant more sensitive to UV radiation, oxidative stress and alkaline stress than the wild type.

Structural Characterization of a Novel Antioxidant Pigment Produced by a Photochromogenic Microbacterium oxydans Strain

The Microbacteriaceae family, such as Microbacterium, is well known for its ability to produce carotenoid-type pigments, but little has been published on the structure of such pigments. Here, we isolated the yellow pigment that is responsible for the yellowish color of a Microbacterium oxydans strain isolated from a decomposing stump of a resinous tree. The pigment, which is synthesized when the bacterium is grown under light, was purified and characterized using several spectroscopic analyses, such as ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonance (¹H NMR, ¹³C NMR), and high-resolution mass spectrometry (HRMS). From these analysis, a molecular formula (C₂₇H₄₂O₂) and a chemical structure (8-hydroxymethyl-2,4,12-trimethyl-14-(2,6,6-trimethyl-cyclohex-2-enyl)-teradeca-3,7,9,11,13-pentan-2-ol) were deduced. The chemical properties of the pigment, such as aqueous stability at different pH, stability in different organic solvents, and antioxidant capacity, are also reported. Together, these data and previous studies have resulted in the identification of a new antioxidant pigment produced by M. oxydans. To the best of our knowledge, this is the first thorough investigation of this carotenoid-like pigment in the Microbacterium genera.

The Lysobacter capsici AZ78 Genome Has a Gene Pool Enabling it to Interact Successfully with Phytopathogenic Microorganisms and Environmental Factors

Lysobacter capsici AZ78 has considerable potential for biocontrol of phytopathogenic microorganisms. However, lack of information about genetic cues regarding its biological characteristics may slow down its exploitation as a biofungicide. In order to obtain a comprehensive overview of genetic features, the L. capsici AZ78 genome was sequenced, annotated and compared with the phylogenetically related pathogens Stenotrophomonas malthophilia K729a and Xanthomonas campestris pv. campestris ATCC 33913. Whole genome comparison, supported by functional analysis, indicated that L. capsici AZ78 has a larger number of genes responsible for interaction with phytopathogens and environmental stress than S. malthophilia K729a and X. c. pv. campestris ATCC 33913. Genes involved in the production of antibiotics, lytic enzymes and siderophores were specific for L. capsici AZ78, as well as genes involved in resistance to antibiotics, environmental stressors, fungicides and heavy metals. The L. capsici AZ78 genome did not encompass genes involved in infection of humans and plants included in the S. malthophilia K729a and X. c. pv. campestris ATCC 33913 genomes, respectively. The L. capsici AZ78 genome provides a genetic framework for detailed analysis of other L. capsici members and the development of novel biofungicides based on this bacterial strain.

Aryl Polyenes, a Highly Abundant Class of Bacterial Natural Products, Are Functionally Related to Antioxidative Carotenoids

Bacterial pigments of the aryl polyene type are structurally similar to the well-known carotenoids with respect to their polyene systems. Their biosynthetic gene cluster is widespread in taxonomically distant bacteria, and four classes of such pigments have been found. Here we report the structure elucidation of the aryl polyene/dialkylresorcinol hybrid pigments of Variovorax paradoxus B4 by HPLC-UV-MS, MALDI-MS and NMR. Furthermore, we show for the first time that this pigment class protects the bacterium from reactive oxygen species, similarly to what is known for carotenoids. An analysis of the distribution of biosynthetic genes for aryl polyenes and carotenoids in bacterial genomes is presented; it shows a complementary distribution of these protective pigments in bacteria.

Phytohormone-mediated interkingdom signaling shapes the outcome of rice-Xanthomonas oryzae pv. oryzae interactions

BACKGROUND

Small-molecule hormones are well known to play key roles in the plant immune signaling network that is activated upon pathogen perception. In contrast, little is known about whether phytohormones also directly influence microbial virulence, similar to what has been reported in animal systems.

RESULTS

In this paper, we tested the hypothesis that hormones fulfill dual roles in plant-microbe interactions by orchestrating host immune responses, on the one hand, and modulating microbial virulence traits, on the other. Employing the rice-Xanthomonas oryzae pv. oryzae (Xoo) interaction as a model system, we show that Xoo uses the classic immune hormone salicylic acid (SA) as a trigger to activate its virulence-associated quorum sensing (QS) machinery. Despite repressing swimming motility, sodium salicylate (NaSA) induced production of the Diffusible Signal Factor (DSF) and Diffusible Factor (DF) QS signals, with resultant accumulation of xanthomonadin and extracellular polysaccharides. In contrast, abscisic acid (ABA), which favors infection by Xoo, had little impact on DF- and DSF-mediated QS, but promoted bacterial swimming via the LuxR solo protein OryR. Moreover, we found both DF and DSF to influence SA- and ABA-responsive gene expression in planta.

CONCLUSIONS

Together our findings indicate that the rice SA and ABA signaling pathways cross-communicate with the Xoo DF and DSF QS systems and underscore the importance of bidirectional interkingdom signaling in molding plant-microbe interactions.

Microbial pigments as natural color sources: current trends and future perspectives

Synthetic colors have been widely used in various industries including food, textile, cosmetic and pharmaceuticals. However toxicity problems caused by synthetic pigments have triggered intense research in natural colors and dyes. Among the natural Sources, pigment producing microorganisms hold a promising potential to meet present day challenges. Furthermore natural colors not only improve the marketability of the product but also add extra features like anti oxidant, anti cancer properties etc. In this review, we present various sources of microbial pigments and to explore their biological and clinical properties like antimicrobial, antioxidant, anticancer and anti inflammatory. The study also emphasizes upon key parameters to improve the bioactivity and production of microbial pigments for their commercial use in pharmacological and medical fields.

Group B streptococcal haemolysin and pigment, a tale of twins

Group B streptococcus [(GBS or Streptococcus agalactiae)] is a leading cause of neonatal meningitis and septicaemia. Most clinical isolates express simultaneously a β-haemolysin/cytolysin and a red polyenic pigment, two phenotypic traits important for GBS identification in medical microbiology. The genetic determinants encoding the GBS haemolysin and pigment have been elucidated and the molecular structure of the pigment has been determined. The cyl operon involved in haemolysin and pigment production is regulated by the major two-component system CovS/R, which coordinates the expression of multiple virulence factors of GBS. Genetic analyses indicated strongly that the haemolysin activity was due to a cytolytic toxin encoded by cylE. However, the biochemical nature of the GBS haemolysin has remained elusive for almost a century because of its instability during purification procedures. Recently, it has been suggested that the haemolytic and cytolytic activity of GBS is due to the ornithine rhamnopolyenic pigment and not to the CylE protein. Here we review and summarize our current knowledge of the genetics, regulation and biochemistry of these twin GBS phenotypic traits, including their functions as GBS virulence factors.

Insights into secondary metabolism from a global analysis of prokaryotic biosynthetic gene clusters

Although biosynthetic gene clusters (BGCs) have been discovered for hundreds of bacterial metabolites, our knowledge of their diversity remains limited. Here, we used a novel algorithm to systematically identify BGCs in the extensive extant microbial sequencing data. Network analysis of the predicted BGCs revealed large gene cluster families, the vast majority uncharacterized. We experimentally characterized the most prominent family, consisting of two subfamilies of hundreds of BGCs distributed throughout the Proteobacteria; their products are aryl polyenes, lipids with an aryl head group conjugated to a polyene tail. We identified a distant relationship to a third subfamily of aryl polyene BGCs, and together the three subfamilies represent the largest known family of biosynthetic gene clusters, with more than 1,000 members. Although these clusters are widely divergent in sequence, their small molecule products are remarkably conserved, indicating for the first time the important roles these compounds play in Gram-negative cell biology.

Identification and biosynthesis of a novel xanthomonadin-dialkylresorcinol-hybrid from Azoarcus sp. BH72

A novel xanthomonadin-dialkylresorcinol hybrid named arcuflavin was identified in Azoarcus sp. BH72 by a combination of feeding experiments, HPLC-MS and MALDI-MS and gene clusters encoding the biosynthesis of this non-isoprenoid aryl-polyene containing pigment are reported. A chorismate-utilizing enzyme from the XanB2-type producing 3- and 4-hydroxybenzoic acid and an AMP-ligase encoded by these gene clusters were characterized, that might perform the first two steps of the polyene biosynthesis. Furthermore, a detailed analysis of the already known or novel biosynthesis gene clusters involved in the biosynthesis of polyene containing pigments like arcuflavin, flexirubin and xanthomonadin revealed the presence of similar gene clusters in a wide range of bacterial taxa, suggesting that polyene and polyene-dialkylresorcinol pigments are more widespread than previously realized.