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Fungus-growing ants depend on a fungal mutualist that can fall prey to fungal pathogens. This mutualist is cultivated by these ants in structures called fungus gardens. Ants exhibit weeding behaviors that keep their fungus gardens healthy by physically removing compromised pieces. However, how ants detect diseases of their fungus gardens is unknown. Here, we applied the logic of Koch’s postulates using environmental fungal community gene sequencing, fungal isolation, and laboratory infection experiments to establishTrichodermaspp. as previously unrecognized pathogens ofTrachymyrmex septentrionalisfungus gardens. Our environmental data showed thatTrichodermaare the most abundant non-cultivar fungi in wildT. septentrionalisfungus gardens. We further determined that metabolites produced byTrichodermainduce an ant weeding response that mirrors their response to liveTrichoderma. Combining ant behavioral experiments with bioactivity-guided fractionation and statistical prioritization of metabolites inTrichodermaextracts demonstrated thatT. septentrionalisants weed in response to peptaibols, a specific class of secondary metabolites known to be produced byTrichodermafungi. Similar assays conducted using purified peptaibols, including the two new peptaibols trichokindins VIII and IX, suggested that weeding is likely induced by peptaibols as a class rather than by a single peptaibol metabolite. In addition to their presence in laboratory experiments, we detected peptaibols in wild fungus gardens. Our combination of environmental data and laboratory infection experiments strongly support that peptaibols act as chemical cues ofTrichodermapathogenesis inT. septentrionalisfungus gardens.Significance StatementAn extended defense response may exist in any relationship where one partner benefits from defending a mutualistic partner. Such a response is observed in the fungus-growing ant symbiosis, where ants must identify and remove pathogens of their symbiotic fungus gardens. Here we describe the fungal pathogenTrichodermaand its associated metabolites, which induceTrachymyrmex septentrionalisant weeding behavior. Ants removed fungus garden pieces inoculated withTrichodermaspores or peptaibol-richTrichodermaextracts, and peptaibols as a class cued ant defensive behavior, allowingT. septentrionalisto differentiate healthy from diseased fungus gardens. Extended defense responses mediated by chemical cues may be underappreciated mechanisms that structure symbiotic interactions.

The emergence of new pathogens and multidrug resistant bacteria is an important public health issue that requires the development of novel classes of antibiotics. Antimicrobial peptides (AMPs) are a promising platform with great potential for the identification of new lead compounds that can combat the aforementioned pathogens due to their broad-spectrum antimicrobial activity and relatively low rate of resistance emergence. AMPs of multicellular organisms made their debut four decades ago thanks to ingenious researchers who asked simple questions about the resistance to bacterial infections of insects. Questions such as "Do fruit flies ever get sick?", combined with pioneering studies, have led to an understanding of AMPs as universal weapons of the immune system. This review focuses on a subclass of AMPs that feature a metal binding motif known as the amino terminal copper and nickel (ATCUN) motif. One of the metal-based strategies of hosts facing a pathogen, it includes wielding the inherent toxicity of copper and deliberately trafficking this metal ion into sites of infection. The sudden increase in the concentration of copper ions in the presence of ATCUN-containing AMPs (ATCUN-AMPs) likely results in a synergistic interaction. Herein, we examine common structural features in ATCUN-AMPs that exist across species, and we highlight unique features that deserve additional attention. We also present the current state of knowledge about the molecular mechanisms behind their antimicrobial activity and the methods available to study this promising class of AMPs.

Small genes (40,000 small-gene families in ~2.3 million phage genome contigs. We find that small genes in phage genomes are approximately 3-fold more prevalent than in host prokaryotic genomes. Our approach enriches for small genes that are translated in microbiomes, suggesting the small genes identified are coding. More than 9,000 families encode potentially secreted or transmembrane proteins, more than 5,000 families encode predicted anti-CRISPR proteins, and more than 500 families encode predicted antimicrobial proteins. By combining homology and genomic-neighborhood analyses, we reveal substantial novelty and diversity within phage biology, including small phage genes found in multiple host phyla, small genes encoding proteins that play essential roles in host infection, and small genes that share genomic neighborhoods and whose encoded proteins may share related functions.

Within social insect colonies, microbiomes often differ between castes due to their different functional roles, and between colony locations. Trachymyrmex septentrionalis fungus-growing ants form colonies throughout the eastern USA and Northern Mexico that include workers, female and male alates (unmated reproductive castes), larvae, and pupae. How T. septentrionalis microbiomes vary across this geographic range and between castes is unknown. Our sampling of individual ants from colonies across the Eastern USA revealed a conserved T. septentrionalis worker ant microbiome, and that worker ant microbiomes are more conserved within colonies than between them. A deeper sampling of individual ants from two colonies that included all available castes (pupae, larvae, workers, female and male alates), from both before and after adaptation to controlled laboratory conditions, revealed that ant microbiomes from each colony, caste, and rearing condition were typically conserved within but not between each sampling category. Tenericute bacterial symbionts were especially abundant in these ant microbiomes and varied widely in abundance between sampling categories. This study demonstrates how individual insect colonies primarily drive the composition of their microbiomes, and that these microbiomes are further modified by developmental differences between insect castes and the different environmental conditions experienced by each colony.IMPORTANCEThis study investigates microbiome assembly in the fungus-growing ant Trachymyrmex septentrionalis, showing how colony, caste, and lab adaptation influences the microbiome and revealing unique patterns of Mollicute symbiont abundance. We find that ant microbiomes differ strongly between colonies but less so within colonies. Microbiomes of different castes and following lab adaptation also differ in a colony-specific manner. This study advances understanding of the nature of individuality in social insect microbiomes, and cautions against the common practice of only sampling a limited number of populations to understand microbiome diversity and function.

Many ant species grow fungus gardens that predigest food as an essential step of the ants' nutrient uptake. These symbiotic fungus gardens have long been studied and feature a gradient of increasing substrate degradation from top to bottom. To further facilitate the study of fungus gardens and enable the understanding of the predigestion process in more detail than currently known, we applied recent mass spectrometry-based approaches and generated a three-dimensional (3D) molecular map of an Atta texana fungus garden to reveal chemical modifications as plant substrates pass through it. The metabolomics approach presented in this study can be applied to study similar processes in natural environments to compare with lab-maintained ecosystems. IMPORTANCE The study of complex ecosystems requires an understanding of the chemical processes involving molecules from several sources. Some of the molecules present in fungus-growing ants' symbiotic system originate from plants. To facilitate the study of fungus gardens from a chemical perspective, we provide a molecular map of an Atta texana fungus garden to reveal chemical modifications as plant substrates pass through it. The metabolomics approach presented in this study can be applied to study similar processes in natural environments.

Virtual conferences can offer significant benefits but require considerable planning and creativity to be successful. Here we describe the successes and failures of a hybrid in-person/virtual conference model. The COVID-19 epidemic presents the scientific community with an opportunity to pioneer novel models that effectively engage virtual participants to advance conference goals.

Although there are numerous studies of firefly mating flashes, lantern bioluminescence, and anti-predation lucibufagin metabolites, almost nothing is known about their microbiome. We therefore used 16S rRNA community amplicon sequencing to characterize the gut and body microbiomes of four North American firefly taxa: Ellychnia corrusca, the Photuris versicolor species complex, Pyractomena borealis, and Pyropyga decipiens. These firefly microbiomes all have very low species diversity, often dominated by a single species, and each firefly type has a characteristic microbiome. Although the microbiomes of male and female fireflies did not differ from each other, Ph. versicolor gut and body microbiomes did, with their gut microbiomes being enriched in Pseudomonas and Acinetobacter. Ellychnia corrusca egg and adult microbiomes were unique except for a single egg microbiome that shared a community type with E. corrusca adults, which could suggest microbial transmission from mother to offspring. Mollicutes that had been previously isolated from fireflies were common in our firefly microbiomes. These results set the stage for further research concerning the function and transmission of these bacterial symbionts.

Spiroplasma platyhelix is a helical bacterium belonging to the class Mollicutes. First isolated from a Pachydiplax longipennis dragonfly, it has the smallest reported Spiroplasma genome size of 740 kbp. Here, we report the genome sequence of S. platyhelix ATCC 51748.

Although there are numerous studies of firefly mating flashes, lantern bioluminescence, and anti-predation lucibufagin metabolites, almost nothing is known about their microbiome. We therefore used 16S rRNA community amplicon sequencing to characterize the gut and body microbiomes of four North American firefly taxa: Ellychnia corrusca, the Photuris versicolor species complex, Pyractomena borealis, and Pyropyga decipiens. These firefly microbiomes all have very low species diversity, often dominated by a single species, and each firefly type has a characteristic microbiome. Although the microbiomes of male and female fireflies did not differ from each other, Ph. versicolor gut and body microbiomes did, with their gut microbiomes being enriched in Pseudomonas and Acinetobacter. Ellychnia corrusca egg and adult microbiomes were unique except for a single egg microbiome that shared a community type with E. corrusca adults, which could suggest microbial transmission from mother to offspring. Mollicutes that had been previously isolated from fireflies were common in our firefly microbiomes. These results set the stage for further research concerning the function and transmission of these bacterial symbionts.

Symbiotic microbes help a myriad of insects acquire nutrients. Recent work suggests that insects also frequently associate with actinobacterial symbionts that produce molecules to help defend against parasites and predators. Here we explore a potential association between Actinobacteria and two species of fungus-farming ambrosia beetles, Xyleborinus saxesenii and Xyleborus affinis. We isolated and identified actinobacterial and fungal symbionts from laboratory reared nests, and characterized small molecules produced by the putative actinobacterial symbionts. One 16S rRNA phylotype of Streptomyces (XylebKG-1) was abundantly and consistently isolated from the galleries and adults of X. saxesenii and X. affinis nests. In addition to Raffaelea sulphurea, the symbiont that X. saxesenii cultivates, we also repeatedly isolated a strain of Nectria sp. that is an antagonist of this mutualism. Inhibition bioassays between Streptomyces griseus XylebKG-1 and the fungal symbionts from X. saxesenii revealed strong inhibitory activity of the actinobacterium toward the fungal antagonist Nectria sp. but not the fungal mutualist R. sulphurea. Bioassay guided HPLC fractionation of S. griseus XylebKG-1 culture extracts, followed by NMR and mass spectrometry, identified cycloheximide as the compound responsible for the observed growth inhibition. A biosynthetic gene cluster putatively encoding cycloheximide was also identified in S. griseus XylebKG-1. The consistent isolation of a single 16S phylotype of Streptomyces from two species of ambrosia beetles, and our finding that a representative isolate of this phylotype produces cycloheximide, which inhibits a parasite of the system but not the cultivated fungus, suggests that these actinobacteria may play defensive roles within these systems.

Experimental manipulations are a key means to establish causal relationships in microbiology. However, challenges remain to establish the applicability of such experiments beyond the precise conditions in which they were conducted. Ecological information can help address these challenges by describing the extent to which an experimentally-determined mechanism can explain the natural phenomenon that it is purported to cause.

Bioassay-guided metabolomic analyses led to the characterization of four new 20-membered glycosylated polyketide macrolactams, macrotermycins A-D, from a termite-associated actinomycete, Amycolatopsis sp. M39. M39's sequenced genome revealed the macrotermycin's putative biosynthetic gene cluster. Macrotermycins A and C had antibacterial activity against human-pathogenic Staphylococcus aureus and, of greater ecological relevance, they also had selective antifungal activity against a fungal parasite of the termite fungal garden.

Two new elaiophylin derivatives, efomycins K (1) and L (2), and five known elaiophylin derivatives (3–7) were isolated from the termite-associated Streptomyces sp. M56. The structures were determined by 1D and 2D NMR and HR-ESIMS analyses and comparative CD spectroscopy. The putative gene cluster responsible for the production of the elaiophylin and efomycin derivatives was identified based on significant homology to related clusters. Phylogenetic analysis of gene cluster domains was used to provide a biosynthetic rational for these new derivatives and to demonstrate how a single biosynthetic pathway can produce diverse structures.

Beewolf wasp eggs release nitrogen oxides to provide protection against fungi and other microbes.

CorrespondenceWe introduce a web-enabled small-molecule mass spectrometry (MS) search engine. To date, no tool can query all the public small-molecule tandem MS data in metabolomics repositories, greatly limiting the utility of these resources in clinical, environmental and natural product applications. Therefore, we introduce aMassSpectrometrySearchTool (MASST) (https://proteosafe-extensions.ucsd.edu/masst/), that enables the discovery of molecular relationships among accessible public metabolomics and natural product tandem mass spectrometry data (MS/MS).

The geographic and phylogenetic scale of ecologically relevant microbial diversity is still poorly understood. Using a model mutualism, fungus-growing ants and their defensive bacterial associate Pseudonocardia, we analyzed genetic diversity and biosynthetic potential in 46 strains isolated from ant colonies in a 20km transect near Barro Colorado Island in Panama. Despite an average pairwise core genome similarity of greater than 99%, population genomic analysis revealed several distinct bacterial populations matching ant host geographic distribution. We identified both genetic diversity signatures and divergent genes distinct to each lineage. We also identify natural product biosynthesis clusters specific to isolation locations. These geographic patterns were observable despite the populations living in close proximity to each other and provides evidence of ongoing genetic exchange. Our results add to the growing body of literature suggesting that variation in traits of interest can be found at extremely fine phylogenetic scales.

Symbiotic microbes help a myriad of insects acquire nutrients. Recent work suggests that insects also frequently associate with actinobacterial symbionts that produce molecules to help defend against parasites and predators. Here we explore a potential association between Actinobacteria and two species of fungus-farming ambrosia beetles,Xyleborinus saxeseniiandXyleborus affinis. We isolated and identified actinobacterial and fungal symbionts from laboratory reared nests, and characterized small molecules produced by the putative actinobacterial symbionts. One 16S rRNA phylotype ofStreptomyces(XylebKG-1) was abundantly and consistently isolated from the nests and adults ofX. saxeseniiandX. affinisnests. In addition toRaffaelea sulphurea, the symbiont thatX. saxeseniicultivates, we also repeatedly isolated a strain ofNectriasp. that is an antagonist of this mutualism. Inhibition bioassays betweenS. griseusXylebKG-1 and the fungal symbionts fromX. saxeseniirevealed strong inhibitory activity of the actinobacterium towards the fungal antagonistNectriasp. but not the fungal mutualistR. sulphurea. Bioassay guided HPLC fractionation ofS. griseusXylebKG-1 culture extracts, followed by NMR and mass spectrometry identified cycloheximide as the compound responsible for the observed growth inhibition. A biosynthetic gene cluster putatively encoding cycloheximide was also identified inS. griseusXylebKG-1. The consistent isolation of a single 16S phylotype ofStreptomycesfrom two species of ambrosia beetles, and our finding that a representative isolate of this phylotype produces cycloheximide, which inhibits a parasite of the system but not the cultivated fungus, suggests that these actinobacteria may play defensive roles within these systems.

Antimicrobial resistance is a global health crisis and few novel antimicrobials have been discovered in recent decades. Natural products, particularly from Streptomyces, are the source of most antimicrobials, yet discovery campaigns focusing on Streptomyces from the soil largely rediscover known compounds. Investigation of understudied and symbiotic sources has seen some success, yet no studies have systematically explored microbiomes for antimicrobials. Here we assess the distinct evolutionary lineages of Streptomyces from insect microbiomes as a source of new antimicrobials through large-scale isolations, bioactivity assays, genomics, metabolomics, and in vivo infection models. Insect-associated Streptomyces inhibit antimicrobial-resistant pathogens more than soil Streptomyces. Genomics and metabolomics reveal their diverse biosynthetic capabilities. Further, we describe cyphomycin, a new molecule active against multidrug resistant fungal pathogens. The evolutionary trajectories of Streptomyces from the insect microbiome influence their biosynthetic potential and ability to inhibit resistant pathogens, supporting the promise of this source in augmenting future antimicrobial discovery., Host microbiomes are feasible sources for drug discovery. Here, using large-scale isolations, bioactivity assays and omics, the authors uncover the antimicrobial potential of insect-associated Streptomyces and identify a compound, cyphomycin, active against multidrug-resistant fungal pathogens.

Microbial ecology research requires sampling strategies that accurately represent the microbial community under study. These communities must typically be transported from the collection location to the laboratory and then stored until they can be processed. However, there is a lack of consensus on how best to preserve microbial communities during transport and storage. Here, we evaluated DESS (Dimethyl sulfoxide, Ethylenediamine tetraacetic acid, Saturated Salt) solution as a broadly applicable preservative for microbial ecology experiments. We stored fungus gardens grown by the ant Trachymyrmex septentrionalis in DESS, 15% glycerol, and phosphate buffered saline (PBS) to test the ability of these preservatives to maintain the structure of fungus garden microbial communities. Variation in microbial community structure due to differences in preservative type was minimal when compared to variation between ant colonies. Additionally, DESS preserved the structure of a defined mock community more faithfully than either 15% glycerol or PBS. DESS is inexpensive, easy to transport, and effective in preserving microbial community structure. We therefore conclude that DESS is a valuable preservative for use in microbial ecology research.

BackgroundShort-read sequencing technologies have made microbial genome sequencing cheap and accessible. However, closing genomes is often costly and assembling short reads from genomes that are repetitive and/or have extreme %GC content remains challenging. Long-read, single-molecule sequencing technologies such as the Oxford Nanopore MinION have the potential to overcome these difficulties, although the best approach for harnessing their potential remains poorly evaluated.ResultsWe sequenced nine bacterial genomes spanning a wide range of GC contents using Illumina MiSeq and Oxford Nanopore MinION sequencing technologies to determine the advantages of each approach, both individually and combined. Assemblies using only MiSeq reads were highly accurate but lacked contiguity, a deficiency that was partially overcome by adding MinION reads to these assemblies. Even more contiguous genome assemblies were generated by using MinION reads for initial assembly, but these were more error-prone and required further polishing. This was especially pronounced when Illumina libraries were biased, as was the case for our strains with both high and low GC content. Increased genome contiguity dramatically improved the annotation of insertion sequences and secondary metabolite biosynthetic gene clusters, likely because long-reads can disambiguate these highly repetitive but biologically important genomic regions.ConclusionsGenome assembly using short-reads is challenged by repetitive sequences and extreme GC contents. Our results indicate that these difficulties can be largely overcome by using single-molecule, long-read sequencing technologies such as the Oxford Nanopore MinION. Using MinION reads for assembly followed by polishing with Illumina reads generated the most contiguous genomes and enabled the accurate annotation of important but difficult to sequence genomic features such as insertion sequences and secondary metabolite biosynthetic gene clusters. The combination of Oxford Nanopore and Illumina sequencing is cost effective and dramatically advances studies of microbial evolution and genome-driven drug discovery.

For their food source, Trachymyrmex septentrionalis ants raise symbiotic fungus gardens that contain bacteria whose functions are poorly understood. Here, we report the genome sequences of eight bacteria isolated from these fungus gardens to better describe the ecology of these strains and their potential to produce secondary metabolites in this niche.

Why does a microorganism associate with a host? What function does it perform? Such questions are difficult to unequivocally address and remain hotly debated. This is partially because scientists often use different philosophical definitions of ‘function’ ambiguously and interchangeably, as exemplified by the controversy surrounding the Encyclopedia of DNA Elements (ENCODE) project. Here, I argue that research studying host-associated microbial communities and their genomes (that is, microbiomes) faces similar pitfalls and that unclear or misapplied conceptions of function underpin many controversies in this field. In particular, experiments that support phenomenological models of function can inappropriately be used to support functional models that instead require specific measurements of evolutionary selection. Microbiome research also requires uniquely clear definitions of ‘who the function is for’, in contrast to most single-organism systems where this is implicit. I illustrate how obscuring either of these issues can lead to substantial confusion and misinterpretation of microbiome function, using the varied conceptions of the holobiont as a current and cogent example. Using clear functional definitions and appropriate types of evidence are essential to effectively communicate microbiome research and foster host health. This Perspective argues that microbiome research needs to consider the different philosophical definitions of function to avoid confusion in the field, and uses the hologenome concept as an example.

The annotation of small molecules is one of the most challenging and important steps in untargeted mass spectrometry analysis, as most of our biological interpretations rely on structural annotations. Molecular networking has emerged as a structured way to organize and mine data from untargeted tandem mass spectrometry (MS/MS) experiments and has been widely applied to propagate annotations. However, propagation is done through manual inspection of MS/MS spectra connected in the spectral networks and is only possible when a reference library spectrum is available. One of the alternative approaches used to annotate an unknown fragmentation mass spectrum is through the use of in silico predictions. One of the challenges of in silico annotation is the uncertainty around the correct structure among the predicted candidate lists. Here we show how molecular networking can be used to improve the accuracy of in silico predictions through propagation of structural annotations, even when there is no match to a MS/MS spectrum in spectral libraries. This is accomplished through creating a network consensus of re-ranked structural candidates using the molecular network topology and structural similarity to improve in silico annotations. The Network Annotation Propagation (NAP) tool is accessible through the GNPS web-platform https://gnps.ucsd.edu/ProteoSAFe/static/gnps-theoretical.jsp., Author summary For genome analysis it is commonly accepted that one can hypothesize the function of genes based on sequence similarity, using annotated reference sequences. Once a homology hypothesis has been made based on reference annotations, it allows one to build hypothesis in terms of function and ultimately understand the underlying biology. In contrast, mass spectrometry (MS) can detect many molecules, as ions, yet we often cannot link a MS signal to a molecule. The reference libraries to annotate fragmented molecular data only cover a small portion of the known molecular space. The use of computational (in silico) fragmentation predictions from structural libraries offers a promising alternative. One of the weaknesses of the molecular annotation using such in silico approaches is that they currently annotate the molecules individually. However, molecular relationships, based on spectral similarity, can be used to enhance the structural hypothesis inferred from the annotation of molecules detected by mass spectrometry. We introduce an online tool called “Network Annotation Propagation” that uses a combination of molecular networks, based on spectral similarity, from which we infer molecular similarity, together with in silico fragmentation, to enable the scientific community to strengthen their MS annotations.

M.H.M. was supported by a Rubicon fellowship of the Netherlands Organization for Scientific Research (NWO;Rubicon 825.13.001). The work of R.K. was supported by the European Union’s Seventh Framework Programme(Joint Call OCEAN.2011–2: Marine microbial diversity—new insights into marine ecosystems functioning and its biotechnological potential) under the grant agreement no.287589 (Micro B3). M.C. was supported by a Biotechnology and Biological Sciences Research Council (BBSRC)studentship (BB/J014478/1). The GSC is supported by funding from the Natural Environment Research Council(UK), the National Institute for Energy Ethics and Society(NIEeS; UK), the Gordon and Betty Moore Foundation,the National Science Foundation (NSF; US) and the US Department of Energy. The Manchester Synthetic Biology Research Centre, SYNBIOCHEM, is supported by BBSRC/Engineering and Physical Sciences Research Council(EPSRC) grant BB/M017702/1, Medema, M.H., Kottmann, R., Yilmaz, P., Cummings, M., Biggins, J.B., Blin, K., De Bruijn, I., Chooi, Y.H., Claesen, J., Coates, R.C., Cruz-Morales, P., Duddela, S., Düsterhus, S., Edwards, D.J., Fewer, D.P., Garg, N., Geiger, C., Gomez-Escribano, J.P., Greule, A., Hadjithomas, M., Haines, A.S., Helfrich, E.J.N., Hillwig, M.L., Ishida, K., Jones, A.C., Jones, C.S., Jungmann, K., Kegler, C., Kim, H.U., Kötter, P., Krug, D., Masschelein, J., Melnik, A.V., Mantovani, S.M., Monroe, E.A., Moore, M., Moss, N., Nützmann, H.-W., Pan, G., Pati, A., Petras, D., Reen, F.J., Rosconi, F., Rui, Z., Tian, Z., Tobias, N.J., Tsunematsu, Y., Wiemann, P., Wyckoff, E., Yan, X., Yim, G., Yu, F., Xie, Y., Aigle, B., Apel, A.K., Balibar, C.J., Balskus, E.P., Barona-Gómez, F., Bechthold, A., Bode, H.B., Borriss, R., Brady, S.F., Brakhage, A.A., Caffrey, P., Cheng, Y.Q., Clardy, J., Cox, R.J., De Mot, R., Donadio, S., Donia, M.S., Van Der Donk, W.A., Dorrestein, P.C., Doyle, S., Driessen, A.J.M., Ehling-Schulz, M., Entian, K.-D., Fischbach, M.A., Gerwick, L., Gerwick, W.H., Gross, H., Gust, B., Hertweck, C., Höfte, M., Jensen, S.E., Ju, J., Katz, L., Kaysser, L., Klassen, J.L., Keller, N.P., Kormanec, J., Kuipers, O.P., Kuzuyama, T., Kyrpides, N.C., Kwon, H.-J., Lautru, S., Lavigne, R., Lee, C.Y., Linquan, B., Liu, X., Liu, W., Luzhetskyy, A., Mahmud, T., Mast, Y., Méndez, C., Metsä-Ketelä, M., Micklefield, J., Mitchell, D.A., Moore, B.S., Moreira, L.M., Müller, R., Neilan, B.A., Nett, M., Nielsen, J., O'Gara, F., Oikawa, H., Osbourn, A., Osburne, M.S., Ostash, B., Payne, S.M., Pernodet, J.-L., Petricek, M., Piel, J., Ploux, O., Raaijmakers, J.M., Salas, J.A., Schmitt, E.K., Scott, B., Seipke, R.F., Shen, B., Sherman, D.H., Sivonen, K., Smanski, M.J., Sosio, M., Stegmann, E., Süssmuth, R.D., Tahlan, K., Thomas, C.M., Tang, Y., Truman, A.W., Viaud, M., Walton, J.D., Walsh, C.T., Weber, T., Van Wezel, G.P., Wilkinson, B., Willey, J.M., Wohlleben, W., Wright, G.D., Ziemert, N., Zhang, C., Zotchev, S.B., Breitling, R., Takano, E., Glöckner, F.O.

Three new dentigerumycin analogues are produced by Streptomyces sp. M41, a bacterium isolated from a South African termite, Macrotermes natalensis. The structures of the complex nonribosomal peptide synthetase–polyketide synthase (NRPS/PKS) hybrid compounds were determined by 1D- and 2D-NMR spectroscopy, high-resolution mass spectrometry, and circular dichroism (CD) spectroscopy. Both cyclic and linear peptides are reported, and the genetic organization of the NRPS modules within the biosynthetic gene cluster accounts for the observed structural diversity.

The discovery of six new, highly substituted tropolone alkaloids, rubterolones A-F, from Actinomadura sp. 5-2, isolated from the gut of the fungus-growing termite Macrotermes natalensis is reported. Rubterolones were identified by using fungus-bacteria challenge assays and a HRMS-based dereplication strategy, and characterised by NMR and HRMS analyses and by X-ray crystallography. Feeding experiments and subsequent chemical derivatisation led to a first library of rubterolone derivatives (A-L). Genome sequencing and comparative analyses revealed their putative biosynthetic pathway, which was supported by feeding experiments. This study highlights how gut microbes can present a prolific source of secondary metabolites.

Oil in subsurface reservoirs is biodegraded by resident microbial communities. Water-mediated, anaerobic conversion of hydrocarbons to methane and CO2, catalyzed by syntrophic bacteria and methanogenic archaea, is thought to be one of the dominant processes. We compared 160 microbial community compositions in ten hydrocarbon resource environments (HREs) and sequenced twelve metagenomes to characterize their metabolic potential. Although anaerobic communities were common, cores from oil sands and coal beds had unexpectedly high proportions of aerobic hydrocarbon-degrading bacteria. Likewise, most metagenomes had high proportions of genes for enzymes involved in aerobic hydrocarbon metabolism. Hence, although HREs may have been strictly anaerobic and typically methanogenic for much of their history, this may not hold today for coal beds and for the Alberta oil sands, one of the largest remaining oil reservoirs in the world. This finding may influence strategies to recover energy or chemicals from these HREs by in situ microbial processes.

Investigators have long recognised the effects of microbial activity on archaeological bone. These investigators, however, have focused on single or groups of microbes rather than on complex microbial aggregates such as biofilms, a focus that has affected our understanding of archaeological bone biodeterioration. In this paper, we report on the investigation of a biofilm in archaeological human bone from the site of Tell Leilan, Syria (2900–1900 BCE). Scanning electron microscopy indicated that the biofilm is characterised by single cells and microcolonies of bacteria and fungi, as well as calcite crystals that were all embedded within extracellular polymeric substances. Using culture techniques and DNA sequencing, we isolated and identified several microbes from the biofilm including Amycolatopsis sp., Penicillium chrysogenum, Aspergillus sp., Chaetomium sp., and Cladosporium sp. Having characterised the Leilan biofilm, we are now closer to understanding the complex process of bone biodeterioration in archaeological bone collections.

Streptomyces sp. AVP053U2 is a marine bacterium isolated from Styela clava , a tunicate collected in Long Island Sound. Here, we report a draft genome for this bacterium, which was found to contain a high capacity for secondary metabolite production based on analysis and identification of numerous biosynthetic gene clusters.

Virtually all multicellular organisms host a community of symbionts composed of mutualistic, commensal, and pathogenic microbes, i.e., their microbiome. The mechanism of selection on host-microbe assemblages remains contentious, particularly regarding whether selection acts differently on hosts and their microbial symbionts. Here, we attempt to reconcile these viewpoints using a model that describes how hosts and their microbial symbionts alter each other’s niche and thereby fitness. We describe how host-microbe interactions might change the shape of the host niche and/or reproductive rates within it, which are directly related to host fitness. A host may also alter the niche of a symbiotic microbe, although this depends on the extent to which that microbe is dependent on the host for reproduction. Finally, we provide a mathematical model to test whether interactions between hosts and microbes are necessary to describe the niche of either partner. Our synthesis highlights the phenotypic effects of host-microbe interactions while respecting the unique lifestyles of each partner, and thereby provides a unified framework to describe how selection might act on a host that is associated with its microbiome.

Streptomyces sp. PTY087I2 is a marine bacterium isolated from Styela canopus , a tunicate collected in Bocas del Toro, Panama. Here, we report a draft genome sequence for this bacterium, found to have 94.7% average nucleotide identity (ANI) with Streptomyces roseosporus NRRL 11379, and containing a diverse suite of secondary metabolite gene clusters.

Given the complexity of host-microbiota symbioses, scientists and philosophers are asking questions at new biological levels of hierarchical organization—what is a holobiont and hologenome? When should this vocabulary be applied? Are these concepts a null hypothesis for host-microbe systems or limited to a certain spectrum of symbiotic interactions such as host-microbial coevolution? Critical discourse is necessary in this nascent area, but productive discourse requires that skeptics and proponents use the same lexicon., Given the complexity of host-microbiota symbioses, scientists and philosophers are asking questions at new biological levels of hierarchical organization—what is a holobiont and hologenome? When should this vocabulary be applied? Are these concepts a null hypothesis for host-microbe systems or limited to a certain spectrum of symbiotic interactions such as host-microbial coevolution? Critical discourse is necessary in this nascent area, but productive discourse requires that skeptics and proponents use the same lexicon. For instance, critiquing the hologenome concept is not synonymous with critiquing coevolution, and arguing that an entity is not a primary unit of selection dismisses the fact that the hologenome concept has always embraced multilevel selection. Holobionts and hologenomes are incontrovertible, multipartite entities that result from ecological, evolutionary, and genetic processes at various levels. They are not restricted to one special process but constitute a wider vocabulary and framework for host biology in light of the microbiome.

The assembly and annotation of the draft genome sequence of Shewanella sp. strain P1-14-1 are reported here to investigate the genes responsible for interkingdom interactions, secondary metabolite production, and microbial electrogenesis.

Microtermolides A (1) and B (2) were isolated from a Streptomyces sp. strain associated with fungus-growing termites. The structures of 1 and 2 were determined by 1D- and 2D-NMR spectroscopy and high-resolution mass spectrometry. Structural elucidation of 1 led to the re-examination of the structure originally proposed for vinylamycin (3). Based on a comparison of predicted and experimental (1)H and (13)C NMR chemical shifts, we propose that vinylamycin's structure be revised from 3 to 4.

The genomes of three Pseudoalteromonas strains (P1-8, P1-11, and P1-30) were sequenced and assembled. These genomes will inform future study of the genes responsible for the production of biologically active compounds responsible for these strains’ antimicrobial, biofouling, and algicidal activities.

We isolated several Hymenobacter-like strains from Victoria Upper Glacier, Antarctica, basal ice that diverged substantially from currently defined Hymenobacter species according to their 16S rRNA and gyrB gene phylogenies. All strains were psychrotolerant, heterotrophic aerobes which grew preferentially on low salt and low nutrient strength agar. Further phenotypic and chemotaxonomic characterization of these isolates supported their assignment as five novel species: H. algoricola sp. nov., H. antarcticus sp. nov., H. elongatus sp. nov., H. fastidiosus sp. nov., and H. glaciei sp. nov. Remarkable among these data was the prevalence of horizontal gene transfers and phenotypic variation, even between apparently closely related strains. These results suggest extensive non-vertical evolution within the genus Hymenobacter, and may reflect evolutionary trajectories resulting from dormancy, e.g., during interment in glacial ice.

Dissolved organic matter (DOM) is an important component of aquatic carbon and nutrient budgets and is a metabolic substrate for organisms at the base of aquatic food chains. Active microbial communities in glaciers affect the abundance and characteristics of organic matter (OM) that is exported to downstream ecosystems. However, how OM is biogeochemically altered in glaciers remains unknown and studies documenting active microbial activity by detecting in situ biogeochemical modifications of OM are lacking due to difficulties characterizing OM and the low concentrations of DOM typical of glacier environments. To address this issue, we measure the abundance and fluorescence characteristics of DOM in basal ice at Victoria Upper Glacier (VUG), McMurdo Dry Valleys, Antarctica. We compare these observations with the results of microbial incubations from the same basal ice samples to determine whether the occurrence of fluorophores indicative of recent microbial activity is linked to the presence of culturable microbial communities containing organisms that could have produced them. Psychrotolerant bacteria were isolated from basal ice samples and were associated with marine humic-like fluorescence. This is interpreted as being indicative of in situ microbial degradation of OM within basal ice at VUG. Marine humic-like material is a recalcitrant form of OM, and its biogeochemical transformation from a relatively labile form of OM in glacier ice may function as a carbon sink.