Lone Gram

Lone Gram
Technical University of Denmark | DTU · Department of Biotechnology and Biomedicine

Ph.D.

About

587
Publications
71,819
Reads
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19,578
Citations
Additional affiliations
January 2013 - present
Technical University of Denmark
Position
  • Professor (Full)
January 2009 - present
University of Maryland, Baltimore
Position
  • Professor (Associate)
March 2000 - December 2012
Technical University of Denmark
Position
  • Professor

Publications

Publications (587)
Article
The broad range of bioactive potentials of cyclodepsipeptides makes these compounds invaluable in the pharmaceutical industry. Recently, a few novel cyclodepsipeptides have been discovered in marine Proteobacteria ; however, their biosynthetic pathways remain to be revealed.
Article
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Many microbial secondary metabolites have been studied for decades primarily because of their antimicrobial properties. However, several of these metabolites also possess non-antimicrobial functions, both influencing the physiology of the producer and their ecological neighbors. An example of a versatile bacterial secondary metabolite with multiple...
Article
Fish pathogenic bacteria of the Tenacibaculum genus are a serious emerging concern in modern aquaculture, causing tenacibaculosis in a broad selection of cultured finfish. Data describing their virulence mechanisms are scarce and few means, antibiotic treatment aside, are available to control their proliferation in aquaculture systems. We genome se...
Article
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As we stand on the brink of the post-antibiotic era, we are in dire need of novel antimicrobial compounds. Microorganisms produce a wealth of so-called secondary metabolites and have been our most prolific source of antibiotics so far. However, rediscovery of known antibiotics from well-studied cultured microorganisms, and the fact that the majorit...
Article
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Pigmented Pseudoalteromonas strains are renowned for their production of secondary metabolites, and genome mining has revealed a high number of biosynthetic gene clusters (BGCs) for which the chemistry is unknown. Identification of those BGCs is a prerequisite for linking products to gene clusters and for further exploitation through heterologous e...
Article
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Species of the genus Pseudomonas are used for several biotechnological purposes, including plant biocontrol and bioremediation. To exploit the Pseudomonas genus in environmental, agricultural, or industrial settings, the organisms must be profiled at the species level as their bioactivity potential differs markedly between species. Standard 16S rRN...
Preprint
Full-text available
Species of the genus Pseudomonas are used for several biotechnological purposes, including plant biocontrol and bioremediation. To exploit the Pseudomonas genus in environmental, agricultural or industrial settings, the organisms must be profiled at species level as their bioactivity potential differs markedly between species. Standard 16S rRNA gen...
Article
Whilst the effects of antibiotics on microorganisms are widely studied, it remains less well-understood how antibiotics affect the physiology of the native producing organisms. Here, using a marine bacterium Photobacterium galatheae S2753 that produces the antibiotic holomycin, we generated a holomycin deficient strain by in-frame deletion of hlmE...
Article
Deciphering the cues that stimulate microorganisms to produce their full secondary metabolic potential promises to speed up the discovery of novel drugs. Ecology-relevant conditions, including carbon-source(s) and microbial interactions, are important effectors of secondary metabolite production. Vice versa, secondary metabolites are important medi...
Article
Plastic is omnipresent in the oceans and serves as surface for biofilm-forming microorganisms. Plastic debris comprises different polymers, which may influence microbial colonization and here, we evaluated if polymer type affects bacterial biofilm formation. Quantifying the biofilm on polyethylene (PE), polypropylene (PP) or polystyrene (PS) pellet...
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Genome mining of pigmented Pseudoalteromonas has revealed a large potential for the production of bioactive compounds and hydrolytic enzymes. The purpose of the present study was to explore this bioactivity potential in a potent antibiotic and enzyme producer, Pseudoalteromonas rubra strain S4059. Proteomic analyses (data are available via Proteome...
Article
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Despite being the world’s third largest ocean, the Indian Ocean is one of the least studied and understood with respect to microbial diversity as well as biogeochemical and ecological functions. In this study, we investigated the microbial community and its metabolic potential for nitrogen (N) acquisition in the oligotrophic surface waters of the I...
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The development and spread of multidrug resistant pathogens have reinforced the urgency to find novel natural products with antibiotic activity. In bacteria, orphan biosynthetic gene clusters (BGCs) far outnumber the BGCs for which chemistry is known, possibly because they are transcriptionally silent under laboratory conditions. A strategy to trig...
Article
Phaeobacter inhibens has been assessed as a probiotic bacterium for application in aquaculture. Studies addressing the efficacy and safety indicate that P. inhibens maintains it antagonistic activity against pathogenic vibrios in aquaculture live cultures (live feed and fish egg/larvae), while having no or a positive effect on the host organisms, a...
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Novel antimicrobials are urgently needed due to the rapid spread of antibiotic resistant bacteria. In a genome-wide analysis of Pseudoalteromonas strains, one strain (S4498) was noticed due to its potent antibiotic activity. It did not produce the yellow antimicrobial pigment bromoalterochromide, which was produced by several related type strains w...
Article
Azoxy compounds belong to a small group of natural products sharing a common functional group with the general structure RN = N + (O −)R. Three new azoxides, azodyrecins A−C (1−3), were isolated from a soil-derived Streptomyces sp. strain P8-A2. The cis-alkenyl unit in 1−3 was found to readily isomerize to the trans-congeners (4− 6). The structures...
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This study comprehensively described the taxonomy and functionality of mangrove microbiomes, including their capacity for secondary metabolite biosynthesis and their ability to resist antibiotics. The microbial taxonomic and functional characteristics differed between geographical locations, corresponding to the environmental condition of two diver...
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Since bacterial resistance to antibiotics is developing worldwide, new antibiotics are needed. Most antibiotics discovered so far have been found in soil-dwelling bacteria, so we instead targeted marine environments as a novel source of bioactive potential. We used amplicon sequencing of bioactive gene clusters in the microbiome of coastal seawater...
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Coating surfaces with a copper-silver alloy in clinical settings can be an alternative or complementary antibacterial strategy to other existing technologies and disinfection interventions. A newly developed copper-silver alloy coating has a high antibacterial efficacy against common pathogenic bacteria in laboratory setups, and the purpose of this...
Article
The Phaeobacter genus has been explored as probiotics in mariculture as a sustainable strategy for prevention of bacterial infections. Its antagonistic effect against common fish pathogens is predominantly due to the production of the antibacterial compound tropodithietic acid (TDA) and TDA-producing strains have repeatedly been isolated from maric...
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Despite the discovery of the first N-acyl homoserine lactone (AHL) based quorum sensing (QS) in the marine environment, relatively little is known about the abundance, nature and diversity of AHL QS systems in this diverse ecosystem. Establishing the prevalence and diversity of AHL QS systems and how they may influence population dynamics within th...
Article
Covering: up to 2019 Humanity is in dire need for novel medicinal compounds with biological activities ranging from antibiotic to anticancer and anti-dementia effects. Recent developments in genome sequencing and mining have revealed an unappreciated potential for bioactive molecule production in marine Proteobacteria. Also, novel bioactive compoun...
Article
Opportunistic pathogenic bacteria readily proliferate in live feed cultures used to feed marine fin fish larvae. As a consequence, larvae cultures fed infected live feed can suffer devastating larvae mortalities. Antibiotics are still used to control these pathogenic bacteria, but due to the risk of antibiotic resistance, sustainable alternatives a...
Article
Full-text available
The antibacterial efficacy of a copper–silver alloy coating under conditions resembling build up of dry surface bacterial biofilms is successfully demonstrated according to US EPA test methods with a ≥99.9% reduction of test organisms over a 24 h period. A tailor-made confocal imaging protocol is designed to visualize in situ the killing of bacteri...
Article
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Infectious bacteria are developing and spreading resistance to conventional treatments at a rapid pace. To provide novel potent antimicrobials, we must develop new bioprospecting strategies. Here, we combined in silico and phenotypic approaches to explore the bioactive potential of the marine bacterial genus Pseudoalteromonas . We found that pigmen...
Article
The Roseobacter group is a widespread marine bacterial group, of which some species produce the broad‐spectrum antibiotic tropodithietic acid (TDA). A mode of action for TDA has previously been proposed in Escherichia coli, but little is known about its effect on non‐producing marine bacteria at in situ concentrations. The purpose of this study was...
Article
An S-methylated analogue of tropodithietic acid (TDA, 1), methyl troposulfenin (2), was isolated from the marine alphaproteobacterium Phaeobacter inhibens. The structure was elucidated by NMR and HRMS. Its inhibitory effect against the fish pathogen Vibrio anguillarum was 4-fold to 100-fold lower than that of the known antibacterial compound TDA. M...
Article
Antimicrobial surfaces such as copper alloys can reduce the spread of pathogenic microorganisms, e.g., in healthcare settings; however, the surface chemistry and thus the antibacterial activity are influenced by environmental parameters such as cleaning and disinfection procedures. Therefore, the purpose of the present study was to assess how coppe...
Article
Full-text available
The production of pentabromopseudilin and related brominated compounds by Pseudoalteromonas spp. has recently been linked to the bmp biosynthetic gene cluster. This study explored the distribution and evolutionary history of this gene cluster in the genus Pseudoalteromonas. A phylogeny of the genus revealed numerous clades that do not contain type...
Article
Full-text available
Bacteria‐host interactions are universal in nature and have significant effects on host functionality. Bacterial secondary metabolites are believed to play key roles in such interactions as well as in interactions within the host‐associated microbial community. Hence, prominent secondary metabolite‐producing bacteria may be strong drivers of microb...
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Our understanding of microbial natural environments combines in situ experimentation with studies of specific interactions in laboratory-based setups. The purpose of this work was to develop, build and demonstrate the use of a microbial culture chamber enabling both in situ and laboratory-based studies. The design uses an enclosed chamber surrounde...
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We present here the genome sequences of Shewanella baltica strain CW2 and Shewanella morhuae strain CW7, isolated from the gastrointestinal tract of Salvelinus namaycush (lean lake trout) and Coregonus clupeaformis (whitefish), respectively. These genome sequences provide insights into the niche adaptation of these specific species in freshwater sy...
Article
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The aquaculture industry is suffering from losses associated with bacterial infections by opportunistic pathogens. Vibrio anguillarum is one of the most important pathogens, causing vibriosis in fish and shellfish cultures leading to high mortalities and economic losses. Bacterial resistance to antibiotics and inefficient vaccination at the larval...
Article
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We present here the whole-genome sequence of Shewanella sp. WE21, an unusual omega-3 fatty acid-producing bacterium isolated from the gastrointestinal tract of the freshwater fish Sander vitreus (walleye). This genome contains a number of unique, large genomic islands with genes not present in other Shewanella bacteria.
Article
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The expanding aquaculture industry plays an important role in feeding the growing human population and with the expansion, sustainable bacterial disease control, such as probiotics, becomes increasingly important. Tropodithietic acid (TDA)‐producing Phaeobacter spp. can protect live feed, for example rotifers and Artemia as well as larvae of turbot...
Preprint
Full-text available
The Roseobacter-group species Phaeobacter inhibens produces the antibacterial tropodithietic acid (TDA) and the algaecidal roseobacticides with both compound classes sharing part of the same biosynthetic pathway. The purpose of this study was to investigate the production of roseobacticides more broadly in TDA-producing roseobacters and to compare...
Article
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The extent of genome divergence and the evolutionary events leading to speciation of marine bacteria have mostly been studied for (locally) abundant, free-living groups. The genus Phaeobacter is found on different marine surfaces, seems to occupy geographically disjunct habitats, and is involved in different biotic interactions, and was therefore t...
Article
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Four heterotrophic, antimicrobial, motile, marine bacterial strains, 27-4(T), 8-1, M6-4.2 and S26, were isolated from aquaculture units in Spain, Denmark and Greece. All four strains produced the antibiotic compound tropodithietic acid, which is a key molecule in their antagonism against fish pathogenic bacteria. Cells of the strains were Gram-reac...
Article
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Vibrionaceae is a large marine bacterial family, which can constitute up to 50% of the prokaryotic population in marine waters. Photobacterium is the second largest genus in the family and we used comparative genomics on 35 strains representing 16 of the 28 species described so far, to understand the genomic diversity present in the Photobacterium...
Article
Whole genome sequencing is increasing used in epidemiology, e.g. for tracing outbreaks of food-borne diseases. This requires in-depth understanding of pathogen emergence, persistence, and genomic diversity along the food production chain including in food processing plants. We sequenced the genomes of 80 isolates of Listeria monocytogenes sampled f...
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Vibrio anguillarum is a marine bacterium that can cause vibriosis in many fish and shellfish species, leading to high mortalities and economic losses in aquaculture. Although putative virulence factors have been identified, the mechanism of pathogenesis of V. Anguillarum is not fully understood. Here, we analyzed wholegenome sequences of a collecti...
Article
Only 1% of marine bacteria are currently culturable using standard laboratory procedures, and this is a major obstacle for our understanding of the biology of marine microorganisms and for the discovery of novel microbial natural products. Therefore, the purpose of this study was to investigate if improved cultivation conditions, including the use...
Article
The ISME Journal: Multidisciplinary Journal of Microbial Ecology is the official Journal of the International Society for Microbial Ecology, publishing high-quality, original research papers, short communications, commentary articles and reviews in the rapidly expanding and diverse discipline of microbial ecology.
Article
Vibrionaceae infections are a major obstacle for marine larviculture; however, little is known about virulence differences of Vibrio strains. The virulence of Vibrio strains, mostly isolated from vibriosis outbreaks in farmed fish, was tested in larval challenge trials with cod (Gadus morhua), turbot (Scophthalmus maximus) and halibut (Hippoglossus...
Article
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Members of the Vibrionaceae family are often associated with chitin-containing organisms, and they are thought to play a major role in chitin degradation. The purpose of the present study was to determine how chitin affects the transcriptome and metabolome of two bioactive Vibrionaceae strains, Vibrio coralliilyticus and Photobacterium galatheae ....
Chapter
Scanning electron microscope (SEM) is increasingly used for morphology characterization in various research fields. The technique is appealing due to the fact that it has a fairly large field of view (µm to mm) with nm lateral resolution, which makes it suitable for characterization of micrometer scale objects, which have nm scale features, such as...
Article
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Chitinolytic microorganisms secrete a range of chitin modifying enzymes, which can be exploited for production of chitin derived products or as fungal or pest control agents. Here, we explored the potential of 11 marine bacteria (Pseudoalteromonadaceae, Vibrionaceae) for chitin degradation using in silico and phenotypic assays. Of 10 chitinolytic s...
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It has previously been reported that some strains of the marine bacterium Pseudoalteromonas luteoviolacea produce the purple bioactive pigment violacein as well as the antibiotic compound indolmycin, hitherto only found in Streptomyces. The purpose of the present study was to determine the relative role of each of these two compounds as antibacteri...
Article
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Tropodithietic acid (TDA)-producing Ruegeria mobilis strains of the Roseobacter clade have primarily been isolated from marine aquaculture and have probiotic potential due to inhibition of fish pathogens. We hypothesized that TDA producers with additional novel features are present in the oceanic environment. We isolated 42 TDA-producing R. mobilis...
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The human pathogenic bacterium Listeria monocytogenes is exposed to antibiotics both during clinical treatment and in its saprophytic life tyle. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial phys...